John Ogness 2de70d744e printk: avoid prb_first_valid_seq() where possible ... [ Upstream commit 13791c80b0cdf54d92fc54221cdf490683b109de ] If message sizes average larger than expected (more than 32 characters), the data_ring will wrap before the desc_ring. Once the data_ring wraps, it will start invalidating descriptors. These invalid descriptors hang around until they are eventually recycled when the desc_ring wraps. Readers do not care about invalid descriptors, but they still need to iterate past them. If the average message size is much larger than 32 characters, then there will be many invalid descriptors preceding the valid descriptors. The function prb_first_valid_seq() always begins at the oldest descriptor and searches for the first valid descriptor. This can be rather expensive for the above scenario. And, in fact, because of its heavy usage in /dev/kmsg, there have been reports of long delays and even RCU stalls. For code that does not need to search from the oldest record, replace prb_first_valid_seq() usage with prb_read_valid_*() functions, which provide a start sequence number to search from. Fixes: 896fbe20b4 ("printk: use the lockless ringbuffer") Reported-by: kernel test robot <oliver.sang@intel.com> Reported-by: J. Avila <elavila@google.com> Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210211173152.1629-1-john.ogness@linutronix.de Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-03-04 11:38:07 +01:00
..
bpf	bpf: Clear subreg_def for global function return values	2021-03-04 11:37:34 +01:00
cgroup	cgroup-v1: add disabled controller check in cgroup1_parse_param()	2021-02-17 11:02:25 +01:00
configs
debug	kdb: Make memory allocations more robust	2021-03-04 11:37:18 +01:00
dma	swiotlb: remove the tbl_dma_addr argument to swiotlb_tbl_map_single	2020-11-02 10:10:39 -05:00
entry	entry: Fix the incorrect ordering of lockdep and RCU check	2020-11-04 18:06:14 +01:00
events	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
gcov	gcov: add support for GCC 10.1	2020-09-11 09:33:54 -07:00
irq	genirq/msi: Activate Multi-MSI early when MSI_FLAG_ACTIVATE_EARLY is set	2021-02-10 09:29:17 +01:00
kcsan	kcsan: Rewrite kcsan_prandom_u32_max() without prandom_u32_state()	2021-03-04 11:37:37 +01:00
livepatch	kernel/: fix repeated words in comments	2020-10-16 11:11:19 -07:00
locking	locking/lockdep: Avoid unmatched unlock	2021-03-04 11:37:47 +01:00
power	PM: hibernate: flush swap writer after marking	2021-02-03 23:28:40 +01:00
printk	printk: avoid prb_first_valid_seq() where possible	2021-03-04 11:38:07 +01:00
rcu	rcu-tasks: Move RCU-tasks initialization to before early_initcall()	2021-01-19 18:27:28 +01:00
sched	sched/eas: Don't update misfit status if the task is pinned	2021-03-04 11:37:44 +01:00
time	tick/sched: Remove bogus boot "safety" check	2021-01-06 14:56:55 +01:00
trace	bpf: Unbreak BPF_PROG_TYPE_KPROBE when kprobe is called via do_int3	2021-02-17 11:02:25 +01:00
.gitignore
acct.c	kernel: acct.c: fix some kernel-doc nits	2020-10-16 11:11:19 -07:00
async.c	treewide: Remove uninitialized_var() usage	2020-07-16 12:35:15 -07:00
audit_fsnotify.c	fsnotify: generalize handle_inode_event()	2020-12-30 11:54:18 +01:00
audit_tree.c	fsnotify: generalize handle_inode_event()	2020-12-30 11:54:18 +01:00
audit_watch.c	fsnotify: generalize handle_inode_event()	2020-12-30 11:54:18 +01:00
audit.c	audit: Remove redundant null check	2020-08-26 09:10:39 -04:00
audit.h	audit: change unnecessary globals into statics	2020-08-17 20:26:58 -04:00
auditfilter.c	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
auditsc.c	audit/stable-5.9 PR 20200803	2020-08-04 14:20:26 -07:00
backtracetest.c	treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD()	2020-07-30 11:15:58 -07:00
bounds.c
capability.c	LSM: Signal to SafeSetID when setting group IDs	2020-10-13 09:17:34 -07:00
compat.c	treewide: Use fallthrough pseudo-keyword	2020-08-23 17:36:59 -05:00
configs.c
context_tracking.c
cpu_pm.c	notifier: Fix broken error handling pattern	2020-09-01 09:58:03 +02:00
cpu.c	kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling	2020-11-27 00:10:39 +11:00
crash_core.c	kdump: append kernel build-id string to VMCOREINFO	2020-08-12 10:58:01 -07:00
crash_dump.c
cred.c
delayacct.c
dma.c
exec_domain.c
exit.c	kernel/io_uring: cancel io_uring before task works	2021-01-30 13:55:18 +01:00
extable.c
fail_function.c	fail_function: Remove a redundant mutex unlock	2020-11-19 11:58:16 -08:00
fork.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
freezer.c
futex.c	futex: Handle faults correctly for PI futexes	2021-01-30 13:55:17 +01:00
gen_kheaders.sh
groups.c	LSM: Signal to SafeSetID when setting group IDs	2020-10-13 09:17:34 -07:00
hung_task.c	kernel/hung_task.c: make type annotations consistent	2020-11-02 12:14:19 -08:00
iomem.c
irq_work.c
jump_label.c	kernel/: fix repeated words in comments	2020-10-16 11:11:19 -07:00
kallsyms.c	treewide: Convert macro and uses of __section(foo) to __section("foo")	2020-10-25 14:51:49 -07:00
kcmp.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c	kcov: make some symbols static	2020-08-12 10:58:02 -07:00
kexec_core.c	kernel: kexec: remove the lock operation of system_transition_mutex	2021-02-03 23:28:37 +01:00
kexec_elf.c
kexec_file.c	ima: Free IMA measurement buffer after kexec syscall	2021-03-04 11:37:50 +01:00
kexec_internal.h
kexec.c	LSM: Introduce kernel_post_load_data() hook	2020-10-05 13:37:03 +02:00
kheaders.c
kmod.c	kmod: remove redundant "be an" in the comment	2020-08-12 10:58:01 -07:00
kprobes.c	kretprobe: Avoid re-registration of the same kretprobe earlier	2021-02-10 09:29:16 +01:00
ksysfs.c
kthread.c	kthread: Extract KTHREAD_IS_PER_CPU	2021-02-07 15:37:17 +01:00
latencytop.c
Makefile	elfcore: fix building with clang	2020-12-11 14:02:14 -08:00
module_signature.c
module_signing.c
module-internal.h
module.c	module: delay kobject uevent until after module init call	2021-01-06 14:56:54 +01:00
notifier.c	notifier: Fix broken error handling pattern	2020-09-01 09:58:03 +02:00
nsproxy.c	nsproxy: support CLONE_NEWTIME with setns()	2020-07-08 11:14:22 +02:00
padata.c	padata: fix possible padata_works_lock deadlock	2020-09-04 17:51:55 +10:00
panic.c	panic: don't dump stack twice on warn	2020-11-14 11:26:04 -08:00
params.c	params: Replace zero-length array with flexible-array member	2020-10-29 17:22:59 -05:00
pid_namespace.c	kernel/: fix repeated words in comments	2020-10-16 11:11:19 -07:00
pid.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
profile.c
ptrace.c	ptrace: Set PF_SUPERPRIV when checking capability	2020-11-17 12:53:22 -08:00
range.c	kernel.h: split out min()/max() et al. helpers	2020-10-16 11:11:19 -07:00
reboot.c	reboot: fix overflow parsing reboot cpu number	2020-11-14 11:26:03 -08:00
regset.c	regset: kill ->get()	2020-07-27 14:31:12 -04:00
relay.c	kernel/relay.c: drop unneeded initialization	2020-10-16 11:11:22 -07:00
resource.c	kernel/resource: make iomem_resource implicit in release_mem_region_adjustable()	2020-10-16 11:11:18 -07:00
rseq.c
scftorture.c	scftorture: Add cond_resched() to test loop	2020-08-24 18:38:38 -07:00
scs.c	mm: memcontrol: account kernel stack per node	2020-08-07 11:33:25 -07:00
seccomp.c	seccomp: Set PF_SUPERPRIV when checking capability	2020-11-17 12:53:22 -08:00
signal.c	ptrace: fix task_join_group_stop() for the case when current is traced	2020-11-02 12:14:19 -08:00
smp.c	smp: Process pending softirqs in flush_smp_call_function_from_idle()	2021-03-04 11:37:51 +01:00
smpboot.c	kthread: Extract KTHREAD_IS_PER_CPU	2021-02-07 15:37:17 +01:00
smpboot.h
softirq.c	softirq: Add debug check to __raise_softirq_irqoff()	2020-09-16 15:18:56 +02:00
stackleak.c	stackleak: let stack_erasing_sysctl take a kernel pointer buffer	2020-09-19 13:13:39 -07:00
stacktrace.c	stacktrace: Remove reliable argument from arch_stack_walk() callback	2020-09-18 14:24:16 +01:00
static_call.c	static_call: Fix return type of static_call_init	2020-10-02 21:18:25 +02:00
stop_machine.c	stop_machine, rcu: Mark functions as notrace	2020-10-26 12:12:27 +01:00
sys_ni.c	mm/madvise: introduce process_madvise() syscall: an external memory hinting API	2020-10-18 09:27:10 -07:00
sys.c	kernel/sys.c: fix prototype of prctl_get_tid_address()	2020-10-25 11:44:16 -07:00
sysctl-test.c
sysctl.c	mm: allow a controlled amount of unfairness in the page lock	2020-09-17 10:26:41 -07:00
task_work.c	task_work: cleanup notification modes	2020-10-17 15:05:30 -06:00
taskstats.c	taskstats: move specifying netlink policy back to ops	2020-10-02 19:11:12 -07:00
test_kprobes.c
torture.c	torture: Dump ftrace at shutdown only if requested	2020-06-29 12:01:45 -07:00
tracepoint.c	tracepoint: Do not fail unregistering a probe due to memory failure	2021-03-04 11:38:03 +01:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c	usermodehelper: reset umask to default before executing user process	2020-10-06 10:31:52 -07:00
up.c
user_namespace.c	kernel/: fix repeated words in comments	2020-10-16 11:11:19 -07:00
user-return-notifier.c
user.c
usermode_driver.c	umd: Stop using split_argv	2020-07-07 11:58:59 -05:00
utsname_sysctl.c
utsname.c
watch_queue.c	watch_queue: Limit the number of watches a user can hold	2020-08-17 09:39:18 -07:00
watchdog_hld.c
watchdog.c	kernel/watchdog: fix watchdog_allowed_mask not used warning	2020-11-14 11:26:03 -08:00
workqueue_internal.h
workqueue.c	workqueue: Restrict affinity change to rescuer	2021-02-07 15:37:17 +01:00