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
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bpf	bpf: Clear subreg_def for global function return values	2021-03-04 11:37:34 +01:00
cgroup
configs
debug	kdb: Make memory allocations more robust	2021-03-04 11:37:18 +01:00
dma
entry
events
gcov
irq
kcsan	kcsan: Rewrite kcsan_prandom_u32_max() without prandom_u32_state()	2021-03-04 11:37:37 +01:00
livepatch
locking	locking/lockdep: Avoid unmatched unlock	2021-03-04 11:37:47 +01:00
power
printk	printk: avoid prb_first_valid_seq() where possible	2021-03-04 11:38:07 +01:00
rcu
sched	sched/eas: Don't update misfit status if the task is pinned	2021-03-04 11:37:44 +01:00
time
trace
.gitignore
acct.c
async.c
audit_fsnotify.c
audit_tree.c
audit_watch.c
audit.c
audit.h
auditfilter.c
auditsc.c
backtracetest.c
bounds.c
capability.c
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c
crash_core.c
crash_dump.c
cred.c
delayacct.c
dma.c
exec_domain.c
exit.c
extable.c
fail_function.c
fork.c
freezer.c
futex.c
gen_kheaders.sh
groups.c
hung_task.c
iomem.c
irq_work.c
jump_label.c
kallsyms.c
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c
kexec_core.c
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
kheaders.c
kmod.c
kprobes.c
ksysfs.c
kthread.c
latencytop.c
Makefile
module_signature.c
module_signing.c
module-internal.h
module.c
notifier.c
nsproxy.c
padata.c
panic.c
params.c
pid_namespace.c
pid.c
profile.c
ptrace.c
range.c
reboot.c
regset.c
relay.c
resource.c
rseq.c
scftorture.c
scs.c
seccomp.c
signal.c
smp.c	smp: Process pending softirqs in flush_smp_call_function_from_idle()	2021-03-04 11:37:51 +01:00
smpboot.c
smpboot.h
softirq.c
stackleak.c
stacktrace.c
static_call.c
stop_machine.c
sys_ni.c
sys.c
sysctl-test.c
sysctl.c
task_work.c
taskstats.c
test_kprobes.c
torture.c
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
up.c
user_namespace.c
user-return-notifier.c
user.c
usermode_driver.c
utsname_sysctl.c
utsname.c
watch_queue.c
watchdog_hld.c
watchdog.c
workqueue_internal.h
workqueue.c