The patch titled
Subject: watchdog/softlockup: fix softlockup_stop_all() hungtask bug
has been added to the -mm tree. Its filename is
watchdog-softlockup-fix-softlockup_stop_all-hungtask-bug.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/watchdog-softlockup-fix-softlockup_stop_all-hungtask-bug.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/watchdog-softlockup-fix-softlockup_stop_all-hungtask-bug.patch
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------------------------------------------------------
From: Jinhui Guo <guojinhui@xxxxxxxxxx>
Subject: watchdog/softlockup: fix softlockup_stop_all() hungtask bug
If NR_CPUS equal to 1, it would trigger hungtask, it can be
triggered by follow command:
echo 0 > /proc/sys/kernel/watchdog
echo 1 > /proc/sys/kernel/watchdog
The hungtask stack:
__schedule
schedule
schedule_timeout
__wait_for_common
softlockup_stop_fn
lockup_detector_reconfigure
proc_watchdog_common
proc_watchdog
proc_sys_call_handler
vfs_write
ksys_write
The watchdog_allowed_mask is completely cleared when the
watchdog is disabled. But the macro for_each_cpu() assume
all masks are "1" when macro NR_CPUS equal to 1. It makes
watchdog_allowed_mask not work at all.
Link: https://lkml.kernel.org/r/20210916175650.1380-1-guojinhui@xxxxxxxxxx
Fixes: be45bf5395e0 ("watchdog/softlockup: Fix cpu_stop_queue_work() double-queue bug")
Signed-off-by: Jinhui Guo <guojinhui@xxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/cpumask.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/include/linux/cpumask.h~watchdog-softlockup-fix-softlockup_stop_all-hungtask-bug
+++ a/include/linux/cpumask.h
@@ -175,10 +175,11 @@ static inline int cpumask_any_distribute
return cpumask_first(srcp);
}
+/* It should check cpumask in some special case, such as watchdog */
#define for_each_cpu(cpu, mask) \
- for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
+ for ((cpu) = 0; (cpu) < 1 && test_bit(0, cpumask_bits(mask)); (cpu)++)
#define for_each_cpu_not(cpu, mask) \
- for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask)
+ for ((cpu) = 0; (cpu) < 1 && !test_bit(0, cpumask_bits(mask)); (cpu)++)
#define for_each_cpu_wrap(cpu, mask, start) \
for ((cpu) = 0; (cpu) < 1; (cpu)++, (void)mask, (void)(start))
#define for_each_cpu_and(cpu, mask1, mask2) \
_
Patches currently in -mm which might be from guojinhui@xxxxxxxxxx are
watchdog-softlockup-fix-softlockup_stop_all-hungtask-bug.patch
