From d72efe7538e9e748ee0a21dd32cd5b39f7d4816d Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Thu, 9 Jun 2016 15:20:05 +0300 Subject: [PATCH] kernel/sysrq, watchdog, sched/core: Reset watchdog on all CPUs while processing sysrq-w commit 57675cb976eff977aefb428e68e4e0236d48a9ff upstream. Lengthy output of sysrq-w may take a lot of time on slow serial console. Currently we reset NMI-watchdog on the current CPU to avoid spurious lockup messages. Sometimes this doesn't work since softlockup watchdog might trigger on another CPU which is waiting for an IPI to proceed. We reset softlockup watchdogs on all CPUs, but we do this only after listing all tasks, and this may be too late on a busy system. So, reset watchdogs CPUs earlier, in for_each_process_thread() loop. Signed-off-by: Andrey Ryabinin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1465474805-14641-1-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: adjust filename, context] Signed-off-by: Ben Hutchings --- kernel/sched.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 7d98d58777bb..fb554299ca44 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6260,14 +6260,16 @@ void show_state_filter(unsigned long state_filter) /* * reset the NMI-timeout, listing all files on a slow * console might take a lot of time: + * Also, reset softlockup watchdogs on all CPUs, because + * another CPU might be blocked waiting for us to process + * an IPI. */ touch_nmi_watchdog(); + touch_all_softlockup_watchdogs(); if (!state_filter || (p->state & state_filter)) sched_show_task(p); } while_each_thread(g, p); - touch_all_softlockup_watchdogs(); - #ifdef CONFIG_SCHED_DEBUG sysrq_sched_debug_show(); #endif -- 2.39.2