forked from luck/tmp_suning_uos_patched
15616ba17d
2070 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Waiman Long
|
fd99aeb978 |
clocksource: Avoid accidental unstable marking of clocksources
[ Upstream commit c86ff8c55b8ae68837b2fa59dc0c203907e9a15f ]
Since commit db3a34e17433 ("clocksource: Retry clock read if long delays
detected") and commit 2e27e793e280 ("clocksource: Reduce clocksource-skew
threshold"), it is found that tsc clocksource fallback to hpet can
sometimes happen on both Intel and AMD systems especially when they are
running stressful benchmarking workloads. Of the 23 systems tested with
a v5.14 kernel, 10 of them have switched to hpet clock source during
the test run.
The result of falling back to hpet is a drastic reduction of performance
when running benchmarks. For example, the fio performance tests can
drop up to 70% whereas the iperf3 performance can drop up to 80%.
4 hpet fallbacks happened during bootup. They were:
[ 8.749399] clocksource: timekeeping watchdog on CPU13: hpet read-back delay of 263750ns, attempt 4, marking unstable
[ 12.044610] clocksource: timekeeping watchdog on CPU19: hpet read-back delay of 186166ns, attempt 4, marking unstable
[ 17.336941] clocksource: timekeeping watchdog on CPU28: hpet read-back delay of 182291ns, attempt 4, marking unstable
[ 17.518565] clocksource: timekeeping watchdog on CPU34: hpet read-back delay of 252196ns, attempt 4, marking unstable
Other fallbacks happen when the systems were running stressful
benchmarks. For example:
[ 2685.867873] clocksource: timekeeping watchdog on CPU117: hpet read-back delay of 57269ns, attempt 4, marking unstable
[46215.471228] clocksource: timekeeping watchdog on CPU8: hpet read-back delay of 61460ns, attempt 4, marking unstable
Commit 2e27e793e280 ("clocksource: Reduce clocksource-skew threshold"),
changed the skew margin from 100us to 50us. I think this is too small
and can easily be exceeded when running some stressful workloads on a
thermally stressed system. So it is switched back to 100us.
Even a maximum skew margin of 100us may be too small in for some systems
when booting up especially if those systems are under thermal stress. To
eliminate the case that the large skew is due to the system being too
busy slowing down the reading of both the watchdog and the clocksource,
an extra consecutive read of watchdog clock is being done to check this.
The consecutive watchdog read delay is compared against
WATCHDOG_MAX_SKEW/2. If the delay exceeds the limit, we assume that
the system is just too busy. A warning will be printed to the console
and the clock skew check is skipped for this round.
Fixes: db3a34e17433 ("clocksource: Retry clock read if long delays detected")
Fixes: 2e27e793e280 ("clocksource: Reduce clocksource-skew threshold")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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Paul E. McKenney
|
cacc6c30e3 |
clocksource: Reduce clocksource-skew threshold
[ Upstream commit 2e27e793e280ff12cb5c202a1214c08b0d3a0f26 ] Currently, WATCHDOG_THRESHOLD is set to detect a 62.5-millisecond skew in a 500-millisecond WATCHDOG_INTERVAL. This requires that clocks be skewed by more than 12.5% in order to be marked unstable. Except that a clock that is skewed by that much is probably destroying unsuspecting software right and left. And given that there are now checks for false-positive skews due to delays between reading the two clocks, it should be possible to greatly decrease WATCHDOG_THRESHOLD, at least for fine-grained clocks such as TSC. Therefore, add a new uncertainty_margin field to the clocksource structure that contains the maximum uncertainty in nanoseconds for the corresponding clock. This field may be initialized manually, as it is for clocksource_tsc_early and clocksource_jiffies, which is copied to refined_jiffies. If the field is not initialized manually, it will be computed at clock-registry time as the period of the clock in question based on the scale and freq parameters to __clocksource_update_freq_scale() function. If either of those two parameters are zero, the tens-of-milliseconds WATCHDOG_THRESHOLD is used as a cowardly alternative to dividing by zero. No matter how the uncertainty_margin field is calculated, it is bounded below by twice WATCHDOG_MAX_SKEW, that is, by 100 microseconds. Note that manually initialized uncertainty_margin fields are not adjusted, but there is a WARN_ON_ONCE() that triggers if any such field is less than twice WATCHDOG_MAX_SKEW. This WARN_ON_ONCE() is intended to discourage production use of the one-nanosecond uncertainty_margin values that are used to test the clock-skew code itself. The actual clock-skew check uses the sum of the uncertainty_margin fields of the two clocksource structures being compared. Integer overflow is avoided because the largest computed value of the uncertainty_margin fields is one billion (10^9), and double that value fits into an unsigned int. However, if someone manually specifies (say) UINT_MAX, they will get what they deserve. Note that the refined_jiffies uncertainty_margin field is initialized to TICK_NSEC, which means that skew checks involving this clocksource will be sufficently forgiving. In a similar vein, the clocksource_tsc_early uncertainty_margin field is initialized to 32*NSEC_PER_MSEC, which replicates the current behavior and allows custom setting if needed in order to address the rare skews detected for this clocksource in current mainline. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20210527190124.440372-4-paulmck@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Yu Liao
|
a9f2c6af5a |
timekeeping: Really make sure wall_to_monotonic isn't positive
commit 4e8c11b6b3f0b6a283e898344f154641eda94266 upstream. Even after commit |
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Michael Pratt
|
f67f6eb717 |
posix-cpu-timers: Clear task::posix_cputimers_work in copy_process()
commit ca7752caeaa70bd31d1714af566c9809688544af upstream.
copy_process currently copies task_struct.posix_cputimers_work as-is. If a
timer interrupt arrives while handling clone and before dup_task_struct
completes then the child task will have:
1. posix_cputimers_work.scheduled = true
2. posix_cputimers_work.work queued.
copy_process clears task_struct.task_works, so (2) will have no effect and
posix_cpu_timers_work will never run (not to mention it doesn't make sense
for two tasks to share a common linked list).
Since posix_cpu_timers_work never runs, posix_cputimers_work.scheduled is
never cleared. Since scheduled is set, future timer interrupts will skip
scheduling work, with the ultimate result that the task will never receive
timer expirations.
Together, the complete flow is:
1. Task 1 calls clone(), enters kernel.
2. Timer interrupt fires, schedules task work on Task 1.
2a. task_struct.posix_cputimers_work.scheduled = true
2b. task_struct.posix_cputimers_work.work added to
task_struct.task_works.
3. dup_task_struct() copies Task 1 to Task 2.
4. copy_process() clears task_struct.task_works for Task 2.
5. Future timer interrupts on Task 2 see
task_struct.posix_cputimers_work.scheduled = true and skip scheduling
work.
Fix this by explicitly clearing contents of task_struct.posix_cputimers_work
in copy_process(). This was never meant to be shared or inherited across
tasks in the first place.
Fixes:
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Greg Kroah-Hartman
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f49fd9882f |
Revert "posix-cpu-timers: Force next expiration recalc after itimer reset"
This reverts commit
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Thomas Gleixner
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3d12ccecfa |
hrtimer: Ensure timerfd notification for HIGHRES=n
[ Upstream commit 8c3b5e6ec0fee18bc2ce38d1dfe913413205f908 ] If high resolution timers are disabled the timerfd notification about a clock was set event is not happening for all cases which use clock_was_set_delayed() because that's a NOP for HIGHRES=n, which is wrong. Make clock_was_set_delayed() unconditially available to fix that. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210713135158.196661266@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Thomas Gleixner
|
aadfa1d6ca |
hrtimer: Avoid double reprogramming in __hrtimer_start_range_ns()
[ Upstream commit 627ef5ae2df8eeccb20d5af0e4cfa4df9e61ed28 ] If __hrtimer_start_range_ns() is invoked with an already armed hrtimer then the timer has to be canceled first and then added back. If the timer is the first expiring timer then on removal the clockevent device is reprogrammed to the next expiring timer to avoid that the pending expiry fires needlessly. If the new expiry time ends up to be the first expiry again then the clock event device has to reprogrammed again. Avoid this by checking whether the timer is the first to expire and in that case, keep the timer on the current CPU and delay the reprogramming up to the point where the timer has been enqueued again. Reported-by: Lorenzo Colitti <lorenzo@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20210713135157.873137732@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Frederic Weisbecker
|
13ccaef77e |
posix-cpu-timers: Force next expiration recalc after itimer reset
[ Upstream commit 406dd42bd1ba0c01babf9cde169bb319e52f6147 ]
When an itimer deactivates a previously armed expiration, it simply doesn't
do anything. As a result the process wide cputime counter keeps running and
the tick dependency stays set until it reaches the old ghost expiration
value.
This can be reproduced with the following snippet:
void trigger_process_counter(void)
{
struct itimerval n = {};
n.it_value.tv_sec = 100;
setitimer(ITIMER_VIRTUAL, &n, NULL);
n.it_value.tv_sec = 0;
setitimer(ITIMER_VIRTUAL, &n, NULL);
}
Fix this with resetting the relevant base expiration. This is similar to
disarming a timer.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210726125513.271824-4-frederic@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
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Thomas Gleixner
|
23e36a8610 |
timers: Move clearing of base::timer_running under base:: Lock
commit bb7262b295472eb6858b5c49893954794027cd84 upstream.
syzbot reported KCSAN data races vs. timer_base::timer_running being set to
NULL without holding base::lock in expire_timers().
This looks innocent and most reads are clearly not problematic, but
Frederic identified an issue which is:
int data = 0;
void timer_func(struct timer_list *t)
{
data = 1;
}
CPU 0 CPU 1
------------------------------ --------------------------
base = lock_timer_base(timer, &flags); raw_spin_unlock(&base->lock);
if (base->running_timer != timer) call_timer_fn(timer, fn, baseclk);
ret = detach_if_pending(timer, base, true); base->running_timer = NULL;
raw_spin_unlock_irqrestore(&base->lock, flags); raw_spin_lock(&base->lock);
x = data;
If the timer has previously executed on CPU 1 and then CPU 0 can observe
base->running_timer == NULL and returns, assuming the timer has completed,
but it's not guaranteed on all architectures. The comment for
del_timer_sync() makes that guarantee. Moving the assignment under
base->lock prevents this.
For non-RT kernel it's performance wise completely irrelevant whether the
store happens before or after taking the lock. For an RT kernel moving the
store under the lock requires an extra unlock/lock pair in the case that
there is a waiter for the timer, but that's not the end of the world.
Reported-by: syzbot+aa7c2385d46c5eba0b89@syzkaller.appspotmail.com
Reported-by: syzbot+abea4558531bae1ba9fe@syzkaller.appspotmail.com
Fixes:
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Frederic Weisbecker
|
6e81e2c38a |
posix-cpu-timers: Fix rearm racing against process tick
commit 1a3402d93c73bf6bb4df6d7c2aac35abfc3c50e2 upstream.
Since the process wide cputime counter is started locklessly from
posix_cpu_timer_rearm(), it can be concurrently stopped by operations
on other timers from the same thread group, such as in the following
unlucky scenario:
CPU 0 CPU 1
----- -----
timer_settime(TIMER B)
posix_cpu_timer_rearm(TIMER A)
cpu_clock_sample_group()
(pct->timers_active already true)
handle_posix_cpu_timers()
check_process_timers()
stop_process_timers()
pct->timers_active = false
arm_timer(TIMER A)
tick -> run_posix_cpu_timers()
// sees !pct->timers_active, ignore
// our TIMER A
Fix this with simply locking process wide cputime counting start and
timer arm in the same block.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Fixes:
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Nicolas Saenz Julienne
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0ff2ea9d8f |
timers: Fix get_next_timer_interrupt() with no timers pending
[ Upstream commit aebacb7f6ca1926918734faae14d1f0b6fae5cb7 ] |
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Paul E. McKenney
|
d9b40ebd44 |
clocksource: Check per-CPU clock synchronization when marked unstable
[ Upstream commit 7560c02bdffb7c52d1457fa551b9e745d4b9e754 ] Some sorts of per-CPU clock sources have a history of going out of synchronization with each other. However, this problem has purportedy been solved in the past ten years. Except that it is all too possible that the problem has instead simply been made less likely, which might mean that some of the occasional "Marking clocksource 'tsc' as unstable" messages might be due to desynchronization. How would anyone know? Therefore apply CPU-to-CPU synchronization checking to newly unstable clocksource that are marked with the new CLOCK_SOURCE_VERIFY_PERCPU flag. Lists of desynchronized CPUs are printed, with the caveat that if it is the reporting CPU that is itself desynchronized, it will appear that all the other clocks are wrong. Just like in real life. Reported-by: Chris Mason <clm@fb.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20210527190124.440372-2-paulmck@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Paul E. McKenney
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03a65c14ab |
clocksource: Retry clock read if long delays detected
[ Upstream commit db3a34e17433de2390eb80d436970edcebd0ca3e ] When the clocksource watchdog marks a clock as unstable, this might be due to that clock being unstable or it might be due to delays that happen to occur between the reads of the two clocks. Yes, interrupts are disabled across those two reads, but there are no shortage of things that can delay interrupts-disabled regions of code ranging from SMI handlers to vCPU preemption. It would be good to have some indication as to why the clock was marked unstable. Therefore, re-read the watchdog clock on either side of the read from the clock under test. If the watchdog clock shows an excessive time delta between its pair of reads, the reads are retried. The maximum number of retries is specified by a new kernel boot parameter clocksource.max_cswd_read_retries, which defaults to three, that is, up to four reads, one initial and up to three retries. If more than one retry was required, a message is printed on the console (the occasional single retry is expected behavior, especially in guest OSes). If the maximum number of retries is exceeded, the clock under test will be marked unstable. However, the probability of this happening due to various sorts of delays is quite small. In addition, the reason (clock-read delays) for the unstable marking will be apparent. Reported-by: Chris Mason <clm@fb.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20210527190124.440372-1-paulmck@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Chen Jun
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af830b27c3 |
posix-timers: Preserve return value in clock_adjtime32()
commit 2d036dfa5f10df9782f5278fc591d79d283c1fad upstream.
The return value on success (>= 0) is overwritten by the return value of
put_old_timex32(). That works correct in the fault case, but is wrong for
the success case where put_old_timex32() returns 0.
Just check the return value of put_old_timex32() and return -EFAULT in case
it is not zero.
[ tglx: Massage changelog ]
Fixes:
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Oleg Nesterov
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4523e648b7 |
kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()
commit 5abbe51a526253b9f003e9a0a195638dc882d660 upstream.
Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.
Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.
Fixes:
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Anna-Maria Behnsen
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df7dbfc24c |
hrtimer: Update softirq_expires_next correctly after __hrtimer_get_next_event()
[ Upstream commit 46eb1701c046cc18c032fa68f3c8ccbf24483ee4 ]
hrtimer_force_reprogram() and hrtimer_interrupt() invokes
__hrtimer_get_next_event() to find the earliest expiry time of hrtimer
bases. __hrtimer_get_next_event() does not update
cpu_base::[softirq_]_expires_next to preserve reprogramming logic. That
needs to be done at the callsites.
hrtimer_force_reprogram() updates cpu_base::softirq_expires_next only when
the first expiring timer is a softirq timer and the soft interrupt is not
activated. That's wrong because cpu_base::softirq_expires_next is left
stale when the first expiring timer of all bases is a timer which expires
in hard interrupt context. hrtimer_interrupt() does never update
cpu_base::softirq_expires_next which is wrong too.
That becomes a problem when clock_settime() sets CLOCK_REALTIME forward and
the first soft expiring timer is in the CLOCK_REALTIME_SOFT base. Setting
CLOCK_REALTIME forward moves the clock MONOTONIC based expiry time of that
timer before the stale cpu_base::softirq_expires_next.
cpu_base::softirq_expires_next is cached to make the check for raising the
soft interrupt fast. In the above case the soft interrupt won't be raised
until clock monotonic reaches the stale cpu_base::softirq_expires_next
value. That's incorrect, but what's worse it that if the softirq timer
becomes the first expiring timer of all clock bases after the hard expiry
timer has been handled the reprogramming of the clockevent from
hrtimer_interrupt() will result in an interrupt storm. That happens because
the reprogramming does not use cpu_base::softirq_expires_next, it uses
__hrtimer_get_next_event() which returns the actual expiry time. Once clock
MONOTONIC reaches cpu_base::softirq_expires_next the soft interrupt is
raised and the storm subsides.
Change the logic in hrtimer_force_reprogram() to evaluate the soft and hard
bases seperately, update softirq_expires_next and handle the case when a
soft expiring timer is the first of all bases by comparing the expiry times
and updating the required cpu base fields. Split this functionality into a
separate function to be able to use it in hrtimer_interrupt() as well
without copy paste.
Fixes:
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Thomas Gleixner
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330c1ee7d5 |
tick/sched: Remove bogus boot "safety" check
[ Upstream commit ba8ea8e7dd6e1662e34e730eadfc52aa6816f9dd ] can_stop_idle_tick() checks whether the do_timer() duty has been taken over by a CPU on boot. That's silly because the boot CPU always takes over with the initial clockevent device. But even if no CPU would have installed a clockevent and taken over the duty then the question whether the tick on the current CPU can be stopped or not is moot. In that case the current CPU would have no clockevent either, so there would be nothing to keep ticking. Remove it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20201206212002.725238293@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org> |
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Zeng Tao
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cb47755725 |
time: Prevent undefined behaviour in timespec64_to_ns()
UBSAN reports: Undefined behaviour in ./include/linux/time64.h:127:27 signed integer overflow: 17179869187 * 1000000000 cannot be represented in type 'long long int' Call Trace: timespec64_to_ns include/linux/time64.h:127 [inline] set_cpu_itimer+0x65c/0x880 kernel/time/itimer.c:180 do_setitimer+0x8e/0x740 kernel/time/itimer.c:245 __x64_sys_setitimer+0x14c/0x2c0 kernel/time/itimer.c:336 do_syscall_64+0xa1/0x540 arch/x86/entry/common.c:295 Commit |
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YueHaibing
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9010e3876e |
timers: Remove unused inline funtion debug_timer_free()
There is no caller in tree, remove it. Signed-off-by: YueHaibing <yuehaibing@huawei.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20200909134749.32300-1-yuehaibing@huawei.com |
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YueHaibing
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5254cb87c0 |
hrtimer: Remove unused inline function debug_hrtimer_free()
There is no caller in tree, remove it. Signed-off-by: YueHaibing <yuehaibing@huawei.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20200909134850.21940-1-yuehaibing@huawei.com |
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Quanyang Wang
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4cd2bb1298 |
time/sched_clock: Mark sched_clock_read_begin/retry() as notrace
Since sched_clock_read_begin() and sched_clock_read_retry() are called
by notrace function sched_clock(), they shouldn't be traceable either,
or else ftrace_graph_caller will run into a dead loop on the path
as below (arm for instance):
ftrace_graph_caller()
prepare_ftrace_return()
function_graph_enter()
ftrace_push_return_trace()
trace_clock_local()
sched_clock()
sched_clock_read_begin/retry()
Fixes:
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Willy Tarreau
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3744741ada |
random32: add noise from network and scheduling activity
With the removal of the interrupt perturbations in previous random32
change (random32: make prandom_u32() output unpredictable), the PRNG
has become 100% deterministic again. While SipHash is expected to be
way more robust against brute force than the previous Tausworthe LFSR,
there's still the risk that whoever has even one temporary access to
the PRNG's internal state is able to predict all subsequent draws till
the next reseed (roughly every minute). This may happen through a side
channel attack or any data leak.
This patch restores the spirit of commit
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George Spelvin
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c51f8f88d7 |
random32: make prandom_u32() output unpredictable
Non-cryptographic PRNGs may have great statistical properties, but are usually trivially predictable to someone who knows the algorithm, given a small sample of their output. An LFSR like prandom_u32() is particularly simple, even if the sample is widely scattered bits. It turns out the network stack uses prandom_u32() for some things like random port numbers which it would prefer are *not* trivially predictable. Predictability led to a practical DNS spoofing attack. Oops. This patch replaces the LFSR with a homebrew cryptographic PRNG based on the SipHash round function, which is in turn seeded with 128 bits of strong random key. (The authors of SipHash have *not* been consulted about this abuse of their algorithm.) Speed is prioritized over security; attacks are rare, while performance is always wanted. Replacing all callers of prandom_u32() is the quick fix. Whether to reinstate a weaker PRNG for uses which can tolerate it is an open question. Commit |
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Linus Torvalds
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41eea65e2a |
Merge tag 'core-rcu-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU changes from Ingo Molnar: - Debugging for smp_call_function() - RT raw/non-raw lock ordering fixes - Strict grace periods for KASAN - New smp_call_function() torture test - Torture-test updates - Documentation updates - Miscellaneous fixes [ This doesn't actually pull the tag - I've dropped the last merge from the RCU branch due to questions about the series. - Linus ] * tag 'core-rcu-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (77 commits) smp: Make symbol 'csd_bug_count' static kernel/smp: Provide CSD lock timeout diagnostics smp: Add source and destination CPUs to __call_single_data rcu: Shrink each possible cpu krcp rcu/segcblist: Prevent useless GP start if no CBs to accelerate torture: Add gdb support rcutorture: Allow pointer leaks to test diagnostic code rcutorture: Hoist OOM registry up one level refperf: Avoid null pointer dereference when buf fails to allocate rcutorture: Properly synchronize with OOM notifier rcutorture: Properly set rcu_fwds for OOM handling torture: Add kvm.sh --help and update help message rcutorture: Add CONFIG_PROVE_RCU_LIST to TREE05 torture: Update initrd documentation rcutorture: Replace HTTP links with HTTPS ones locktorture: Make function torture_percpu_rwsem_init() static torture: document --allcpus argument added to the kvm.sh script rcutorture: Output number of elapsed grace periods rcutorture: Remove KCSAN stubs rcu: Remove unused "cpu" parameter from rcu_report_qs_rdp() ... |
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Linus Torvalds
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ed016af52e |
These are the locking updates for v5.10:
- Add deadlock detection for recursive read-locks. The rationale is outlined
in:
224ec489d3cd: ("lockdep/Documention: Recursive read lock detection reasoning")
The main deadlock pattern we want to detect is:
TASK A: TASK B:
read_lock(X);
write_lock(X);
read_lock_2(X);
- Add "latch sequence counters" (seqcount_latch_t):
A sequence counter variant where the counter even/odd value is used to
switch between two copies of protected data. This allows the read path,
typically NMIs, to safely interrupt the write side critical section.
We utilize this new variant for sched-clock, and to make x86 TSC handling safer.
- Other seqlock cleanups, fixes and enhancements
- KCSAN updates
- LKMM updates
- Misc updates, cleanups and fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'locking-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
"These are the locking updates for v5.10:
- Add deadlock detection for recursive read-locks.
The rationale is outlined in commit
|
||
|
Linus Torvalds
|
f5f59336a9 |
Updates for timekeeping, timers and related drivers:
Core:
- Early boot support for the NMI safe timekeeper by utilizing
local_clock() up to the point where timekeeping is initialized. This
allows printk() to store multiple timestamps in the ringbuffer which is
useful for coordinating dmesg information across a fleet of machines.
- Provide a multi-timestamp accessor for printk()
- Make timer init more robust by checking for invalid timer flags.
- Comma vs. semicolon fixes
Drivers:
- Support for new platforms in existing drivers (SP804 and Renesas CMT)
- Comma vs. semicolon fixes
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Merge tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
"Updates for timekeeping, timers and related drivers:
Core:
- Early boot support for the NMI safe timekeeper by utilizing
local_clock() up to the point where timekeeping is initialized.
This allows printk() to store multiple timestamps in the ringbuffer
which is useful for coordinating dmesg information across a fleet
of machines.
- Provide a multi-timestamp accessor for printk()
- Make timer init more robust by checking for invalid timer flags.
- Comma vs semicolon fixes
Drivers:
- Support for new platforms in existing drivers (SP804 and Renesas
CMT)
- Comma vs semicolon fixes
* tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
clocksource/drivers/armada-370-xp: Use semicolons rather than commas to separate statements
clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements
timers: Mask invalid flags in do_init_timer()
clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode
clocksource/drivers/sp804: Add support for Hisilicon sp804 timer
clocksource/drivers/sp804: Support non-standard register offset
clocksource/drivers/sp804: Prepare for support non-standard register offset
clocksource/drivers/sp804: Remove a mismatched comment
clocksource/drivers/sp804: Delete the leading "__" of some functions
clocksource/drivers/sp804: Remove unused sp804_timer_disable() and timer-sp804.h
clocksource/drivers/sp804: Cleanup clk_get_sys()
dt-bindings: timer: renesas,cmt: Document r8a774e1 CMT support
dt-bindings: timer: renesas,cmt: Document r8a7742 CMT support
alarmtimer: Convert comma to semicolon
timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
|
||
|
Ingo Molnar
|
e705d39796 |
Merge branch 'locking/urgent' into locking/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Ingo Molnar
|
b36c830f8c |
Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull v5.10 RCU changes from Paul E. McKenney: - Debugging for smp_call_function(). - Strict grace periods for KASAN. The point of this series is to find RCU-usage bugs, so the corresponding new RCU_STRICT_GRACE_PERIOD Kconfig option depends on both DEBUG_KERNEL and RCU_EXPERT, and is further disabled by dfefault. Finally, the help text includes a goodly list of scary caveats. - New smp_call_function() torture test. - Torture-test updates. - Documentation updates. - Miscellaneous fixes. Signed-off-by: Ingo Molnar <mingo@kernel.org> |
||
|
Qianli Zhao
|
b952caf2d5 |
timers: Mask invalid flags in do_init_timer()
do_init_timer() accepts any combination of timer flags handed in by the caller without a sanity check, but only TIMER_DEFFERABLE, TIMER_PINNED and TIMER_IRQSAFE are valid. If the supplied flags have other bits set, this could result in malfunction. If bits are set in TIMER_CPUMASK the first timer usage could deference a cpu base which is outside the range of possible CPUs. If TIMER_MIGRATION is set, then the switch_timer_base() will live lock. Prevent that with a sanity check which warns when invalid flags are supplied and masks them out. [ tglx: Made it WARN_ON_ONCE() and added context to the changelog ] Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/9d79a8aa4eb56713af7379f99f062dedabcde140.1597326756.git.zhaoqianli@xiaomi.com |
||
|
Stephen Boyd
|
f9e62f318f |
treewide: Make all debug_obj_descriptors const
This should make it harder for the kernel to corrupt the debug object descriptor, used to call functions to fixup state and track debug objects, by moving the structure to read-only memory. Signed-off-by: Stephen Boyd <swboyd@chromium.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20200815004027.2046113-3-swboyd@chromium.org |
||
|
Ahmed S. Darwish
|
249d053835 |
timekeeping: Use seqcount_latch_t
Latch sequence counters are a multiversion concurrency control mechanism where the seqcount_t counter even/odd value is used to switch between two data storage copies. This allows the seqcount_t read path to safely interrupt its write side critical section (e.g. from NMIs). Initially, latch sequence counters were implemented as a single write function, raw_write_seqcount_latch(), above plain seqcount_t. The read path was expected to use plain seqcount_t raw_read_seqcount(). A specialized read function was later added, raw_read_seqcount_latch(), and became the standardized way for latch read paths. Having unique read and write APIs meant that latch sequence counters are basically a data type of their own -- just inappropriately overloading plain seqcount_t. The seqcount_latch_t data type was thus introduced at seqlock.h. Use that new data type instead of seqcount_raw_spinlock_t. This ensures that only latch-safe APIs are to be used with the sequence counter. Note that the use of seqcount_raw_spinlock_t was not very useful in the first place. Only the "raw_" subset of seqcount_t APIs were used at timekeeping.c. This subset was created for contexts where lockdep cannot be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the seqcount_t writer serialization lock is held -- cannot thus be done. References: |
||
|
Ahmed S. Darwish
|
a690ed0735 |
time/sched_clock: Use seqcount_latch_t
Latch sequence counters have unique read and write APIs, and thus seqcount_latch_t was recently introduced at seqlock.h. Use that new data type instead of plain seqcount_t. This adds the necessary type-safety and ensures only latching-safe seqcount APIs are to be used. Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200827114044.11173-5-a.darwish@linutronix.de |
||
|
Ahmed S. Darwish
|
58faf20a08 |
time/sched_clock: Use raw_read_seqcount_latch() during suspend
sched_clock uses seqcount_t latching to switch between two storage places protected by the sequence counter. This allows it to have interruptible, NMI-safe, seqcount_t write side critical sections. Since |
||
|
Xu Wang
|
ec02821c1d |
alarmtimer: Convert comma to semicolon
Replace a comma between expression statements by a semicolon. Signed-off-by: Xu Wang <vulab@iscas.ac.cn> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Stephen Boyd <sboyd@kernel.org> Link: https://lore.kernel.org/r/20200818062651.21680-1-vulab@iscas.ac.cn |
||
|
Paul E. McKenney
|
bca37119c5 |
tick-sched: Clarify "NOHZ: local_softirq_pending" warning
Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH" (where "HH" is the hexadecimal softirq vector number) when one or more non-RCU softirq handlers are still enabled when checking to stop the scheduler-tick interrupt. This message is not as enlightening as one might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #HH". Reported-by: Andy Lutomirski <luto@kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> |
||
|
Gustavo A. R. Silva
|
df561f6688 |
treewide: Use fallthrough pseudo-keyword
Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> |
||
|
Thomas Gleixner
|
e2d977c9f1 |
timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.
Provide an interface to retrieve all three timestamps in one go.
There are some caveats:
1) Boot time and late sleep time injection
Boot time is a racy access on 32bit systems if the sleep time injection
happens late during resume and not in timekeeping_resume(). That could be
avoided by expanding struct tk_read_base with boot offset for 32bit and
adding more overhead to the update. As this is a hard to observe once per
resume event which can be filtered with reasonable effort using the
accurate mono/real timestamps, it's probably not worth the trouble.
Aside of that it might be possible on 32 and 64 bit to observe the
following when the sleep time injection happens late:
CPU 0 CPU 1
timekeeping_resume()
ktime_get_fast_timestamps()
mono, real = __ktime_get_real_fast()
inject_sleep_time()
update boot offset
boot = mono + bootoffset;
That means that boot time already has the sleep time adjustment, but
real time does not. On the next readout both are in sync again.
Preventing this for 64bit is not really feasible without destroying the
careful cache layout of the timekeeper because the sequence count and
struct tk_read_base would then need two cache lines instead of one.
2) Suspend/resume timestamps
Access to the time keeper clock source is disabled accross the innermost
steps of suspend/resume. The accessors still work, but the timestamps
are frozen until time keeping is resumed which happens very early.
For regular suspend/resume there is no observable difference vs. sched
clock, but it might affect some of the nasty low level debug printks.
OTOH, access to sched clock is not guaranteed accross suspend/resume on
all systems either so it depends on the hardware in use.
If that turns out to be a real problem then this could be mitigated by
using sched clock in a similar way as during early boot. But it's not as
trivial as on early boot because it needs some careful protection
against the clock monotonic timestamp jumping backwards on resume.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
|
||
|
Thomas Gleixner
|
71419b30ca |
timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
During early boot the NMI safe timekeeper returns 0 until the first clocksource becomes available. This prevents it from being used for printk or other facilities which today use sched clock. sched clock can be available way before timekeeping is initialized. The obvious workaround for this is to utilize the early sched clock in the default dummy clock read function until a clocksource becomes available. After switching to the clocksource clock MONOTONIC and BOOTTIME will not jump because the timekeeping_init() bases clock MONOTONIC on sched clock and the offset between clock MONOTONIC and BOOTTIME is zero during boot. Clock REALTIME cannot provide useful timestamps during early boot up to the point where a persistent clock becomes available, which is either in timekeeping_init() or later when the RTC driver which might depend on I2C or other subsystems is initialized. There is a minor difference to sched_clock() vs. suspend/resume. As the timekeeper clock source might not be accessible during suspend, after timekeeping_suspend() timestamps freeze up to the point where timekeeping_resume() is invoked. OTOH this is true for some sched clock implementations as well. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20200814115512.041422402@linutronix.de |
||
|
Linus Torvalds
|
b923f1247b |
A set oftimekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the counter
read function when time namespace support is enabled. Adding the pointer
is a NOOP for all other architectures because the compiler is supposed
to optimize that out when it is unused in the architecture specific
inline. The change also solved a similar problem for MIPS which
fortunately has time namespaces not yet enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another sequence
counter in the S390 implementation. A better solution is to utilize the
already existing VDSO sequence count for this. The core code now exposes
helper functions which allow to serialize against the timekeeper code
and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It now has
an embedded architecture specific struct embedded which defaults to an
empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support to
work from a common upstream base.
- A trivial comment fix.
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Merge tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping updates from Thomas Gleixner:
"A set of timekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
implementation.
S390 requires that the VDSO data pointer is handed in to the
counter read function when time namespace support is enabled.
Adding the pointer is a NOOP for all other architectures because
the compiler is supposed to optimize that out when it is unused in
the architecture specific inline. The change also solved a similar
problem for MIPS which fortunately has time namespaces not yet
enabled.
S390 needs to update clock related VDSO data independent of the
timekeeping updates. This was solved so far with yet another
sequence counter in the S390 implementation. A better solution is
to utilize the already existing VDSO sequence count for this. The
core code now exposes helper functions which allow to serialize
against the timekeeper code and against concurrent readers.
S390 needs extra data for their clock readout function. The initial
common VDSO data structure did not provide a way to add that. It
now has an embedded architecture specific struct embedded which
defaults to an empty struct.
Doing this now avoids tree dependencies and conflicts post rc1 and
allows all other architectures which work on generic VDSO support
to work from a common upstream base.
- A trivial comment fix"
* tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time: Delete repeated words in comments
lib/vdso: Allow to add architecture-specific vdso data
timekeeping/vsyscall: Provide vdso_update_begin/end()
vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()
|
||
|
Linus Torvalds
|
b6b178e38f |
A set of posix CPU timer changes which allows to defer the heavy work of
posix CPU timers into task work context. The tick interrupt is reduced to a quick check which queues the work which is doing the heavy lifting before returning to user space or going back to guest mode. Moving this out is deferring the signal delivery slightly but posix CPU timers are inaccurate by nature as they depend on the tick so there is no real damage. The relevant test cases all passed. This lifts the last offender for RT out of the hard interrupt context tick handler, but it also has the general benefit that the actual heavy work is accounted to the task/process and not to the tick interrupt itself. Further optimizations are possible to break long sighand lock hold and interrupt disabled (on !RT kernels) times when a massive amount of posix CPU timers (which are unpriviledged) is armed for a task/process. This is currently only enabled for x86 because the architecture has to ensure that task work is handled in KVM before entering a guest, which was just established for x86 with the new common entry/exit code which got merged post 5.8 and is not the case for other KVM architectures. -----BEGIN PGP SIGNATURE----- iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAl82sRkTHHRnbHhAbGlu dXRyb25peC5kZQAKCRCmGPVMDXSYoUs2D/9IZuALnVXtnvsOQh5uMRpxr/I6tpQm KJSRkcSSne9rIV3dQlswDdaT7bGibd7pbKQOnlA0vc37vDwaJHEzmTOJGpHpHnMA fHH2QP3LL2oZ1d7DG6eNJESCmaFBcaYXNbKtluOWQzHQhd9P8yHb4N+kzfxHK0Fr uNd+cd6T658xPsNOLaLP3MG2Yz0rVt2F5c1v8n78NfibeKckYhPov8cwVrf2WGWr XFHKorx4lXZ+vFwKEeZ7qQtqvAsLDixgMkFfY2GGSPhd1AMAaIUICZgsdEj2gg7H YK+lwA0uoqPaXshOCmdkCLkfPA7BRmAySWE7jUPbIvRqM94Uapk9+4CqjgiH1Qs+ T8CWbcZk8tZACFrouhZkhrnjUTev/vE7oirsjn26DRY68/Ec7llpCOjvVA7HZWqN vJ/BN35IufA7WEkf2TWNv5mg1zIlHI0O17zDifFq4g2VKFDVvQB0QYWlvug/eAu9 zYNX3WwA/IP8C9EOHZt54e6AKH8F3dT04oLFUkmRIcVKv1SEbdFufVfV7RavPEwK P21JNXPDdd0aLUO7ksqyQN7pyR3puGXSCb5NAPtZY6UWSMN4G/3SVry3mJa/0BJd mn+uYGpo9vmceh90vAHBoGIena/pez/PyRLWgGeT9jMjk95rNY0sEhaLEAOF9AR5 ck+3K2rY0S3wwQ== =Reot -----END PGP SIGNATURE----- Merge tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull more timer updates from Thomas Gleixner: "A set of posix CPU timer changes which allows to defer the heavy work of posix CPU timers into task work context. The tick interrupt is reduced to a quick check which queues the work which is doing the heavy lifting before returning to user space or going back to guest mode. Moving this out is deferring the signal delivery slightly but posix CPU timers are inaccurate by nature as they depend on the tick so there is no real damage. The relevant test cases all passed. This lifts the last offender for RT out of the hard interrupt context tick handler, but it also has the general benefit that the actual heavy work is accounted to the task/process and not to the tick interrupt itself. Further optimizations are possible to break long sighand lock hold and interrupt disabled (on !RT kernels) times when a massive amount of posix CPU timers (which are unpriviledged) is armed for a task/process. This is currently only enabled for x86 because the architecture has to ensure that task work is handled in KVM before entering a guest, which was just established for x86 with the new common entry/exit code which got merged post 5.8 and is not the case for other KVM architectures" * tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Select POSIX_CPU_TIMERS_TASK_WORK posix-cpu-timers: Provide mechanisms to defer timer handling to task_work posix-cpu-timers: Split run_posix_cpu_timers() |
||
|
Linus Torvalds
|
97d052ea3f |
A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in various
situations caused by the lockdep additions to seqcount to validate that
the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict per
CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored and
write_seqcount_begin() has a lockdep assertion to validate that the
lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API is
unchanged and determines the type at compile time with the help of
_Generic which is possible now that the minimal GCC version has been
moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs which
have been addressed already independent of this.
While generaly useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if the
writers are serialized by an associated lock, which leads to the well
known reader preempts writer livelock. RT prevents this by storing the
associated lock pointer independent of lockdep in the seqcount and
changing the reader side to block on the lock when a reader detects
that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
"A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in
various situations caused by the lockdep additions to seqcount to
validate that the write side critical sections are non-preemptible.
- The seqcount associated lock debug addons which were blocked by the
above fallout.
seqcount writers contrary to seqlock writers must be externally
serialized, which usually happens via locking - except for strict
per CPU seqcounts. As the lock is not part of the seqcount, lockdep
cannot validate that the lock is held.
This new debug mechanism adds the concept of associated locks.
sequence count has now lock type variants and corresponding
initializers which take a pointer to the associated lock used for
writer serialization. If lockdep is enabled the pointer is stored
and write_seqcount_begin() has a lockdep assertion to validate that
the lock is held.
Aside of the type and the initializer no other code changes are
required at the seqcount usage sites. The rest of the seqcount API
is unchanged and determines the type at compile time with the help
of _Generic which is possible now that the minimal GCC version has
been moved up.
Adding this lockdep coverage unearthed a handful of seqcount bugs
which have been addressed already independent of this.
While generally useful this comes with a Trojan Horse twist: On RT
kernels the write side critical section can become preemtible if
the writers are serialized by an associated lock, which leads to
the well known reader preempts writer livelock. RT prevents this by
storing the associated lock pointer independent of lockdep in the
seqcount and changing the reader side to block on the lock when a
reader detects that a writer is in the write side critical section.
- Conversion of seqcount usage sites to associated types and
initializers"
* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
locking/seqlock, headers: Untangle the spaghetti monster
locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
x86/headers: Remove APIC headers from <asm/smp.h>
seqcount: More consistent seqprop names
seqcount: Compress SEQCNT_LOCKNAME_ZERO()
seqlock: Fold seqcount_LOCKNAME_init() definition
seqlock: Fold seqcount_LOCKNAME_t definition
seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
hrtimer: Use sequence counter with associated raw spinlock
kvm/eventfd: Use sequence counter with associated spinlock
userfaultfd: Use sequence counter with associated spinlock
NFSv4: Use sequence counter with associated spinlock
iocost: Use sequence counter with associated spinlock
raid5: Use sequence counter with associated spinlock
vfs: Use sequence counter with associated spinlock
timekeeping: Use sequence counter with associated raw spinlock
xfrm: policy: Use sequence counters with associated lock
netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
netfilter: conntrack: Use sequence counter with associated spinlock
sched: tasks: Use sequence counter with associated spinlock
...
|
||
|
Randy Dunlap
|
b0294f3025 |
time: Delete repeated words in comments
Drop repeated words in kernel/time/. {when, one, into}
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/r/20200807033248.8452-1-rdunlap@infradead.org
|
||
|
Thomas Gleixner
|
1fb497dd00 |
posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
Running posix CPU timers in hard interrupt context has a few downsides: - For PREEMPT_RT it cannot work as the expiry code needs to take sighand lock, which is a 'sleeping spinlock' in RT. The original RT approach of offloading the posix CPU timer handling into a high priority thread was clumsy and provided no real benefit in general. - For fine grained accounting it's just wrong to run this in context of the timer interrupt because that way a process specific CPU time is accounted to the timer interrupt. - Long running timer interrupts caused by a large amount of expiring timers which can be created and armed by unpriviledged user space. There is no hard requirement to expire them in interrupt context. If the signal is targeted at the task itself then it won't be delivered before the task returns to user space anyway. If the signal is targeted at a supervisor process then it might be slightly delayed, but posix CPU timers are inaccurate anyway due to the fact that they are tied to the tick. Provide infrastructure to schedule task work which allows splitting the posix CPU timer code into a quick check in interrupt context and a thread context expiry and signal delivery function. This has to be enabled by architectures as it requires that the architecture specific KVM implementation handles pending task work before exiting to guest mode. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de |
||
|
Thomas Gleixner
|
820903c784 |
posix-cpu-timers: Split run_posix_cpu_timers()
Split it up as a preparatory step to move the heavy lifting out of interrupt context. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20200730102337.677439437@linutronix.de |
||
|
Thomas Gleixner
|
19d0070a27 |
timekeeping/vsyscall: Provide vdso_update_begin/end()
Architectures can have the requirement to add additional architecture specific data to the VDSO data page which needs to be updated independent of the timekeeper updates. To protect these updates vs. concurrent readers and a conflicting update through timekeeping, provide helper functions to make such updates safe. vdso_update_begin() takes the timekeeper_lock to protect against a potential update from timekeeper code and increments the VDSO sequence count to signal data inconsistency to concurrent readers. vdso_update_end() makes the sequence count even again to signal data consistency and drops the timekeeper lock. [ Sven: Add interrupt disable handling to the functions ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200804150124.41692-3-svens@linux.ibm.com |
||
|
Linus Torvalds
|
442489c219 |
Time, timers and related driver updates:
- Prevent unnecessary timer softirq invocations by extending the tracking
of the next expiring timer in the timer wheel beyond the existing NOHZ
functionality. The tracking overhead at enqueue time is within the
noise, but on sensitive workloads the avoidance of the soft interrupt
invocation is a measurable improvement.
- The obligatory new clocksource driver for Ingenic X100 OST
- The usual fixes, improvements, cleanups and extensions for newer chip
variants all over the driver space.
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Merge tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Time, timers and related driver updates:
- Prevent unnecessary timer softirq invocations by extending the
tracking of the next expiring timer in the timer wheel beyond the
existing NOHZ functionality.
The tracking overhead at enqueue time is within the noise, but on
sensitive workloads the avoidance of the soft interrupt invocation
is a measurable improvement.
- The obligatory new clocksource driver for Ingenic X100 OST
- The usual fixes, improvements, cleanups and extensions for newer
chip variants all over the driver space"
* tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
timers: Recalculate next timer interrupt only when necessary
clocksource/drivers/ingenic: Add support for the Ingenic X1000 OST.
dt-bindings: timer: Add Ingenic X1000 OST bindings.
clocksource/drivers: Replace HTTP links with HTTPS ones
clocksource/drivers/nomadik-mtu: Handle 32kHz clock
clocksource/drivers/sh_cmt: Use "kHz" for kilohertz
clocksource/drivers/imx: Add support for i.MX TPM driver with ARM64
clocksource/drivers/ingenic: Add high resolution timer support for SMP/SMT.
timers: Lower base clock forwarding threshold
timers: Remove must_forward_clk
timers: Spare timer softirq until next expiry
timers: Expand clk forward logic beyond nohz
timers: Reuse next expiry cache after nohz exit
timers: Always keep track of next expiry
timers: Optimize _next_timer_interrupt() level iteration
timers: Add comments about calc_index() ceiling work
timers: Move trigger_dyntick_cpu() to enqueue_timer()
timers: Use only bucket expiry for base->next_expiry value
timers: Preserve higher bits of expiration on index calculation
clocksource/drivers/timer-atmel-tcb: Add sama5d2 support
...
|
||
|
Linus Torvalds
|
0a72761b27 |
threads-v5.9
-----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCXygcLwAKCRCRxhvAZXjc ohajAP4n5E3BmN0jpIviXT4eNhP62jzxJtxlVXtgGT3D8b1mpQEA5n8NSOlQLoAh yUGsjtwR9xDcHMcrhXD3yN6eYJSK0A8= =tn4R -----END PGP SIGNATURE----- Merge tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull thread updates from Christian Brauner: "This contains the changes to add the missing support for attaching to time namespaces via pidfds. Last cycle setns() was changed to support attaching to multiple namespaces atomically. This requires all namespaces to have a point of no return where they can't fail anymore. Specifically, <namespace-type>_install() is allowed to perform permission checks and install the namespace into the new struct nsset that it has been given but it is not allowed to make visible changes to the affected task. Once <namespace-type>_install() returns, anything that the given namespace type additionally requires to be setup needs to ideally be done in a function that can't fail or if it fails the failure must be non-fatal. For time namespaces the relevant functions that fell into this category were timens_set_vvar_page() and vdso_join_timens(). The latter could still fail although it didn't need to. This function is only implemented for vdso_join_timens() in current mainline. As discussed on-list (cf. [1]), in order to make setns() support time namespaces when attaching to multiple namespaces at once properly we changed vdso_join_timens() to always succeed. So vdso_join_timens() replaces the mmap_write_lock_killable() with mmap_read_lock(). Please note that arm is about to grow vdso support for time namespaces (possibly this merge window). We've synced on this change and arm64 also uses mmap_read_lock(), i.e. makes vdso_join_timens() a function that can't fail. Once the changes here and the arm64 changes have landed, vdso_join_timens() should be turned into a void function so it's obvious to callers and implementers on other architectures that the expectation is that it can't fail. We didn't do this right away because it would've introduced unnecessary merge conflicts between the two trees for no major gain. As always, tests included" [1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein * tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: tests: add CLONE_NEWTIME setns tests nsproxy: support CLONE_NEWTIME with setns() timens: add timens_commit() helper timens: make vdso_join_timens() always succeed |
||
|
Linus Torvalds
|
e4cbce4d13 |
The main changes in this cycle were:
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the values
become larger. This is now replaced with more precise arithmetics,
using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Improve uclamp performance by using a static key for the fast path
- Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
better power efficiency of RT tasks on battery powered devices.
(The default is to maximize performance & reduce RT latencies.)
- Improve utime and stime tracking accuracy, which had a fixed boundary
of error, which created larger and larger relative errors as the
values become larger. This is now replaced with more precise
arithmetics, using the new mul_u64_u64_div_u64() helper in math64.h.
- Improve the deadline scheduler, such as making it capacity aware
- Improve frequency-invariant scheduling
- Misc cleanups in energy/power aware scheduling
- Add sched_update_nr_running tracepoint to track changes to nr_running
- Documentation additions and updates
- Misc cleanups and smaller fixes
* tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst
sched/doc: Document capacity aware scheduling
sched: Document arch_scale_*_capacity()
arm, arm64: Fix selection of CONFIG_SCHED_THERMAL_PRESSURE
Documentation/sysctl: Document uclamp sysctl knobs
sched/uclamp: Add a new sysctl to control RT default boost value
sched/uclamp: Fix a deadlock when enabling uclamp static key
sched: Remove duplicated tick_nohz_full_enabled() check
sched: Fix a typo in a comment
sched/uclamp: Remove unnecessary mutex_init()
arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE
sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
arch_topology, sched/core: Cleanup thermal pressure definition
trace/events/sched.h: fix duplicated word
linux/sched/mm.h: drop duplicated words in comments
smp: Fix a potential usage of stale nr_cpus
sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
sched: nohz: stop passing around unused "ticks" parameter.
sched: Better document ttwu()
sched: Add a tracepoint to track rq->nr_running
...
|
||
|
Linus Torvalds
|
8f0cb6660a |
These are the latest RCU bits for v5.9:
- kfree_rcu updates - RCU tasks updates - Read-side scalability tests - SRCU updates - Torture-test updates - Documentation updates - Miscellaneous fixes Signed-off-by: Ingo Molnar <mingo@kernel.org> -----BEGIN PGP SIGNATURE----- iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAl8n80ERHG1pbmdvQGtl cm5lbC5vcmcACgkQEnMQ0APhK1gauA/+NtuExW9V9cPDZ8AAp6x6QfoEIgqN4VEk pYuyP0+ZbmwH+h8z7qPqMrwxUHQnhef7gqtlWa7wj9MawbEbmqnA/3uivjX/3Aao bGMMXkqXppc6hgwktgLNk8vfq3LRVEH2P0i0I+Tymgxu3DCHSGRep4LWfdAS/q3z 4pe5JXqdMx+Qnfy/bsVxJTaJAncMq1LQNAtWY1TIwK8L8RmpXrj5dvuLKUr7q+zl P+BfXyrdX+x05TpmHHnI/bR3w9yASL32E0S3IaQYRRqH8TsUIGHWe13Ib6hKXXG5 j7W5KrsOgr0fQBxi+JW2fgGQkrua4o7yk4H2Ygj+Fi5RvP2uqNZdvXFAlP2cUMu/ 7Pg8+7kC6jKIrwpD03s9ZZzm0QN3jsCxFs2PEkkHMzjXbe1CI4tIkTH6ex1uvjR2 v3OhCIp6ypxpEIJbFQucia0iQ4NF+evKjqCvRkbepqQ096jg+CNFh0VG0Tp8XR+y Gk9B9oXvLLPMd6ah5CI9nLJKiMWVRV8mvvqspoblGo//+39ksh4mzxm865tFXYg4 C+DPJvKlY15Ib5eJ/xr8EZ/oS0K2sUF9sMYnK4P8QMhyTBMbpAZiljHYK+Wujt8I g/JCWxrEMv3LHPY9/guB5Nod/Qb4Jqqm9iE9qEX3MQxtt2O2nmmWd91pzFcUXlFU RDBWYJ63Okg= =rNhf -----END PGP SIGNATURE----- Merge tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: - kfree_rcu updates - RCU tasks updates - Read-side scalability tests - SRCU updates - Torture-test updates - Documentation updates - Miscellaneous fixes * tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (109 commits) torture: Remove obsolete "cd $KVM" torture: Avoid duplicate specification of qemu command torture: Dump ftrace at shutdown only if requested torture: Add kvm-tranform.sh script for qemu-cmd files torture: Add more tracing crib notes to kvm.sh torture: Improve diagnostic for KCSAN-incapable compilers torture: Correctly summarize build-only runs torture: Pass --kmake-arg to all make invocations rcutorture: Check for unwatched readers torture: Abstract out console-log error detection torture: Add a stop-run capability torture: Create qemu-cmd in --buildonly runs rcu/rcutorture: Replace 0 with false torture: Add --allcpus argument to the kvm.sh script torture: Remove whitespace from identify_qemu_vcpus output rcutorture: NULL rcu_torture_current earlier in cleanup code rcutorture: Handle non-statistic bang-string error messages torture: Set configfile variable to current scenario rcutorture: Add races with task-exit processing locktorture: Use true and false to assign to bool variables ... |
||
|
Linus Torvalds
|
145ff1ec09 |
arm64 and cross-arch updates for 5.9:
- Removal of the tremendously unpopular read_barrier_depends() barrier,
which is a NOP on all architectures apart from Alpha, in favour of
allowing architectures to override READ_ONCE() and do whatever dance
they need to do to ensure address dependencies provide LOAD ->
LOAD/STORE ordering. This work also offers a potential solution if
compilers are shown to convert LOAD -> LOAD address dependencies into
control dependencies (e.g. under LTO), as weakly ordered architectures
will effectively be able to upgrade READ_ONCE() to smp_load_acquire().
The latter case is not used yet, but will be discussed further at LPC.
- Make the MSI/IOMMU input/output ID translation PCI agnostic, augment
the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
bus-specific parameter and apply the resulting changes to the device
ID space provided by the Freescale FSL bus.
- arm64 support for TLBI range operations and translation table level
hints (part of the ARMv8.4 architecture version).
- Time namespace support for arm64.
- Export the virtual and physical address sizes in vmcoreinfo for
makedumpfile and crash utilities.
- CPU feature handling cleanups and checks for programmer errors
(overlapping bit-fields).
- ACPI updates for arm64: disallow AML accesses to EFI code regions and
kernel memory.
- perf updates for arm64.
- Miscellaneous fixes and cleanups, most notably PLT counting
optimisation for module loading, recordmcount fix to ignore
relocations other than R_AARCH64_CALL26, CMA areas reserved for
gigantic pages on 16K and 64K configurations.
- Trivial typos, duplicate words.
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 and cross-arch updates from Catalin Marinas:
"Here's a slightly wider-spread set of updates for 5.9.
Going outside the usual arch/arm64/ area is the removal of
read_barrier_depends() series from Will and the MSI/IOMMU ID
translation series from Lorenzo.
The notable arm64 updates include ARMv8.4 TLBI range operations and
translation level hint, time namespace support, and perf.
Summary:
- Removal of the tremendously unpopular read_barrier_depends()
barrier, which is a NOP on all architectures apart from Alpha, in
favour of allowing architectures to override READ_ONCE() and do
whatever dance they need to do to ensure address dependencies
provide LOAD -> LOAD/STORE ordering.
This work also offers a potential solution if compilers are shown
to convert LOAD -> LOAD address dependencies into control
dependencies (e.g. under LTO), as weakly ordered architectures will
effectively be able to upgrade READ_ONCE() to smp_load_acquire().
The latter case is not used yet, but will be discussed further at
LPC.
- Make the MSI/IOMMU input/output ID translation PCI agnostic,
augment the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
bus-specific parameter and apply the resulting changes to the
device ID space provided by the Freescale FSL bus.
- arm64 support for TLBI range operations and translation table level
hints (part of the ARMv8.4 architecture version).
- Time namespace support for arm64.
- Export the virtual and physical address sizes in vmcoreinfo for
makedumpfile and crash utilities.
- CPU feature handling cleanups and checks for programmer errors
(overlapping bit-fields).
- ACPI updates for arm64: disallow AML accesses to EFI code regions
and kernel memory.
- perf updates for arm64.
- Miscellaneous fixes and cleanups, most notably PLT counting
optimisation for module loading, recordmcount fix to ignore
relocations other than R_AARCH64_CALL26, CMA areas reserved for
gigantic pages on 16K and 64K configurations.
- Trivial typos, duplicate words"
Link: http://lkml.kernel.org/r/20200710165203.31284-1-will@kernel.org
Link: http://lkml.kernel.org/r/20200619082013.13661-1-lorenzo.pieralisi@arm.com
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (82 commits)
arm64: use IRQ_STACK_SIZE instead of THREAD_SIZE for irq stack
arm64/mm: save memory access in check_and_switch_context() fast switch path
arm64: sigcontext.h: delete duplicated word
arm64: ptrace.h: delete duplicated word
arm64: pgtable-hwdef.h: delete duplicated words
bus: fsl-mc: Add ACPI support for fsl-mc
bus/fsl-mc: Refactor the MSI domain creation in the DPRC driver
of/irq: Make of_msi_map_rid() PCI bus agnostic
of/irq: make of_msi_map_get_device_domain() bus agnostic
dt-bindings: arm: fsl: Add msi-map device-tree binding for fsl-mc bus
of/device: Add input id to of_dma_configure()
of/iommu: Make of_map_rid() PCI agnostic
ACPI/IORT: Add an input ID to acpi_dma_configure()
ACPI/IORT: Remove useless PCI bus walk
ACPI/IORT: Make iort_msi_map_rid() PCI agnostic
ACPI/IORT: Make iort_get_device_domain IRQ domain agnostic
ACPI/IORT: Make iort_match_node_callback walk the ACPI namespace for NC
arm64: enable time namespace support
arm64/vdso: Restrict splitting VVAR VMA
arm64/vdso: Handle faults on timens page
...
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