On Mon, Jul 20, 2015 at 06:14:27PM -0400, Sasha Levin wrote: > On 05/19/2015 03:17 AM, tip-bot for Frederic Weisbecker wrote: > > Commit-ID: b30f0e3ffedfa52b1d67a302ae5860c49998e5e2 > > Gitweb: > > http://git.kernel.org/tip/b30f0e3ffedfa52b1d67a302ae5860c49998e5e2 > > Author: Frederic Weisbecker <[email protected]> > > AuthorDate: Tue, 12 May 2015 16:41:49 +0200 > > Committer: Ingo Molnar <[email protected]> > > CommitDate: Tue, 19 May 2015 08:39:12 +0200 > > > > sched/preempt: Optimize preemption operations on __schedule() callers > > > > __schedule() disables preemption and some of its callers > > (the preempt_schedule*() family) also set PREEMPT_ACTIVE. > > > > So we have two preempt_count() modifications that could be performed > > at once. > > > > Lets remove the preemption disablement from __schedule() and pull > > this responsibility to its callers in order to optimize preempt_count() > > operations in a single place. > > > > Suggested-by: Linus Torvalds <[email protected]> > > Signed-off-by: Frederic Weisbecker <[email protected]> > > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Cc: Thomas Gleixner <[email protected]> > > Link: > > http://lkml.kernel.org/r/[email protected] > > Signed-off-by: Ingo Molnar <[email protected]> > > Hi all, > > I was seeing RCU stall warnings that appeared to have different backtrace > each time, but would reliably trigger when fuzzing and looked something like > this: > > [4394886.414687] INFO: rcu_preempt detected stalls on CPUs/tasks: > [4394886.416717] Tasks blocked on level-0 rcu_node (CPUs 0-23): P13356 > [4394886.418699] (detected by 2, t=20502 jiffies, g=3548, c=3547, > q=120) > [4394886.420712] trinity-c42 R running task 26936 13356 9574 > 0x10000000 > [4394886.422466] ffff8807d1c7fbe8 ffff8807d1c7fb88 0000000000000022 > ffff8801081e1bb0 > [4394886.423711] ffff8801081e1b88 ffff8807d1eb8780 ffff8801081e11d8 > ffff8807e2564000 > [4394886.424956] ffff8807d1eb8000 ffff8807d1c7fbd8 ffff8807d1c78000 > 0000000000000000 > [4394886.426196] Call Trace: > [4394886.426627] preempt_schedule_irq (./arch/x86/include/asm/paravirt.h:807 > kernel/sched/core.c:3218) > [4394886.427582] ? lockdep_reset_lock (kernel/locking/lockdep.c:3105) > [4394886.428548] ? kill_pid_info (include/linux/rcupdate.h:857 > kernel/signal.c:1340) > [4394886.429438] retint_kernel (arch/x86/entry/entry_64.S:578) > [4394886.430286] ? kill_pid_info (include/linux/rcupdate.h:857 > kernel/signal.c:1340) > [4394886.431176] ? native_restore_fl (./arch/x86/include/asm/irqflags.h:35) > [4394886.432376] lock_is_held (kernel/locking/lockdep.c:3661) > [4394886.433241] ? kill_pid_info (include/linux/rcupdate.h:914 > kernel/signal.c:1344) > [4394886.434135] rcu_read_lock_held (kernel/rcu/update.c:275) > [4394886.435012] pid_task (kernel/pid.c:440 (discriminator 5)) > [4394886.435656] kill_pid_info (kernel/signal.c:1341) > [4394886.436351] ? kill_pid_info (include/linux/rcupdate.h:857 > kernel/signal.c:1340) > [4394886.437065] SYSC_kill (kernel/signal.c:1426 kernel/signal.c:2903) > [4394886.437726] ? SYSC_kill (include/linux/rcupdate.h:857 > kernel/signal.c:1425 kernel/signal.c:2903) > [4394886.438419] ? find_get_pid (include/linux/rcupdate.h:914 > kernel/pid.c:494) > [4394886.439134] ? kill_pid (kernel/signal.c:2894) > [4394886.439782] ? find_get_pid (kernel/pid.c:497) > [4394886.440492] ? find_get_pid (kernel/pid.c:489) > [4394886.441183] ? lock_is_held (kernel/locking/lockdep.c:3661) > [4394886.441929] ? rcu_read_lock_sched_held (kernel/rcu/update.c:109) > [4394886.442772] ? syscall_trace_enter_phase2 (arch/x86/entry/common.c:196) > [4394886.443632] SyS_kill (kernel/signal.c:2893) > [4394886.444255] tracesys_phase2 (arch/x86/entry/entry_64.S:270) > > I worked with Paul to rule out RCU as the cause. > > I've noticed that all traces had one thing in common: being stuck in > preempt_schedule_irq(), > so I've looked at recent changes there and noticed this commit. > > I've tried testing the commit before that, and the problem went away. > Checking out this > commit the problem reappeared.
Do you have any idea how to reproduce that? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
