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SubjectRe: [tip:sched/urgent] sched/cputime: Don't use smp_processor_id() in preemptible context
On Fri, Jul 14, 2017 at 02:10:14AM -0700, tip-bot for Wanpeng Li wrote:
> Commit-ID: 0e4097c3354e2f5a5ad8affd9dc7f7f7d00bb6b9
> Gitweb: http://git.kernel.org/tip/0e4097c3354e2f5a5ad8affd9dc7f7f7d00bb6b9
> Author: Wanpeng Li <wanpeng.li@hotmail.com>
> AuthorDate: Sun, 9 Jul 2017 00:40:28 -0700
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 14 Jul 2017 10:27:15 +0200
>
> sched/cputime: Don't use smp_processor_id() in preemptible context
>
> Recent kernels trigger this warning:
>
> BUG: using smp_processor_id() in preemptible [00000000] code: 99-trinity/181
> caller is debug_smp_processor_id+0x17/0x19
> CPU: 0 PID: 181 Comm: 99-trinity Not tainted 4.12.0-01059-g2a42eb9 #1
> Call Trace:
> dump_stack+0x82/0xb8
> check_preemption_disabled()
> debug_smp_processor_id()
> vtime_delta()
> task_cputime()
> thread_group_cputime()
> thread_group_cputime_adjusted()
> wait_consider_task()
> do_wait()
> SYSC_wait4()
> do_syscall_64()
> entry_SYSCALL64_slow_path()
>
> As Frederic pointed out:
>
> | Although those sched_clock_cpu() things seem to only matter when the
> | sched_clock() is unstable. And that stability is a condition for nohz_full
> | to work anyway. So probably sched_clock() alone would be enough.
>
> This patch fixes it by replacing sched_clock_cpu() with sched_clock() to
> avoid calling smp_processor_id() in a preemptible context.
>
> Reported-by: Xiaolong Ye <xiaolong.ye@intel.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: http://lkml.kernel.org/r/1499586028-7402-1-git-send-email-wanpeng.li@hotmail.com
> [ Prettified the changelog. ]
> Signed-off-by: Ingo Molnar <mingo@kernel.org>

Thanks! The patch looks good!

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