git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 57675cb976eff977aefb428e68e4e0236d48a9ff Mon Sep 17 00:00:00 2001
   2 From: Andrey Ryabinin <aryabinin@virtuozzo.com>
   3 Date: Thu, 9 Jun 2016 15:20:05 +0300
   4 Subject: kernel/sysrq, watchdog, sched/core: Reset watchdog on all CPUs while processing sysrq-w
   5
   6 From: Andrey Ryabinin <aryabinin@virtuozzo.com>
   7
   8 commit 57675cb976eff977aefb428e68e4e0236d48a9ff upstream.
   9
  10 Lengthy output of sysrq-w may take a lot of time on slow serial console.
  11
  12 Currently we reset NMI-watchdog on the current CPU to avoid spurious
  13 lockup messages. Sometimes this doesn't work since softlockup watchdog
  14 might trigger on another CPU which is waiting for an IPI to proceed.
  15 We reset softlockup watchdogs on all CPUs, but we do this only after
  16 listing all tasks, and this may be too late on a busy system.
  17
  18 So, reset watchdogs CPUs earlier, in for_each_process_thread() loop.
  19
  20 Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
  21 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  22 Cc: Peter Zijlstra <peterz@infradead.org>
  23 Cc: Thomas Gleixner <tglx@linutronix.de>
  24 Link: http://lkml.kernel.org/r/1465474805-14641-1-git-send-email-aryabinin@virtuozzo.com
  25 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  26 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  27
  28 ---
  29  kernel/sched/core.c |    6 ++++--
  30  1 file changed, 4 insertions(+), 2 deletions(-)
  31
  32 --- a/kernel/sched/core.c
  33 +++ b/kernel/sched/core.c
  34 @@ -4951,14 +4951,16 @@ void show_state_filter(unsigned long sta
  35                 /*
  36                  * reset the NMI-timeout, listing all files on a slow
  37                  * console might take a lot of time:
  38 +                * Also, reset softlockup watchdogs on all CPUs, because
  39 +                * another CPU might be blocked waiting for us to process
  40 +                * an IPI.
  41                  */
  42                 touch_nmi_watchdog();
  43 +               touch_all_softlockup_watchdogs();
  44                 if (!state_filter || (p->state & state_filter))
  45                         sched_show_task(p);
  46         }
  47
  48 -       touch_all_softlockup_watchdogs();
  49 -
  50  #ifdef CONFIG_SCHED_DEBUG
  51         sysrq_sched_debug_show();
  52  #endif