The patch titled
Subject: watchdog: Fix a watchdog crash in some configurations
has been added to the -mm tree. Its filename is
watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix.patch
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------------------------------------------------------
From: John Hubbard <jhubbard@xxxxxxxxxx>
Subject: watchdog: Fix a watchdog crash in some configurations
Commit 8fcf2cc768acd845c1fed837bf9cfe2d7106336d in linux-next introduced a
regression in some configurations. Specifically, with CONFIG_NO_HZ_FULL
set, and CONFIG_NO_HZ_FULL_ALL *not* set, the kernel will crash in
lockup_detector_init(), due to a NULL tick_nohz_full_mask pointer.
This is because the above commit uses tick_nohz_full_mask (in
lockup_detector_init), if CONFIG_NO_HZ_FULL is set, but
tick_nohz_full_mask only gets allocated if either:
a) CONFIG_NO_HZ_FULL_ALL is set, or
b) Someone passes in nohz_full=<any_value> on the boot
args line.
To correct this, change lockup_detector_init so that it does a runtime
check instead of the ifdef check. This fix is simpler than my original
proposed fix, thanks to Chris Metcalf for that.
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff -puN kernel/watchdog.c~watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix kernel/watchdog.c
--- a/kernel/watchdog.c~watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix
+++ a/kernel/watchdog.c
@@ -920,14 +920,14 @@ void __init lockup_detector_init(void)
{
set_sample_period();
-#ifdef CONFIG_NO_HZ_FULL
- if (!cpumask_empty(tick_nohz_full_mask))
- pr_info("Disabling watchdog on nohz_full cores by default\n");
- cpumask_andnot(&watchdog_cpumask, cpu_possible_mask,
- tick_nohz_full_mask);
-#else
- cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
-#endif
+ if (tick_nohz_full_enabled()) {
+ if (!cpumask_empty(tick_nohz_full_mask))
+ pr_info("Disabling watchdog on nohz_full cores by default\n");
+ cpumask_andnot(&watchdog_cpumask, cpu_possible_mask,
+ tick_nohz_full_mask);
+ }
+ else
+ cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
if (watchdog_enabled)
watchdog_enable_all_cpus();
_
Patches currently in -mm which might be from jhubbard@xxxxxxxxxx are
watchdog-add-watchdog_cpumask-sysctl-to-assist-nohz-fix.patch
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