From: John Hubbard <jhubbard@xxxxxxxxxx>
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 (in addition to the ifdef check). This now
matches the way most of the other CONFIG_NO_HZ_FULL code does
it's checking. This fix is a little simpler than my original
proposed fix, thanks to Chris Metcalf for that.
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
kernel/watchdog.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 40fda2f..910d73f 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -921,10 +921,14 @@ 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);
+ 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);
#else
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
#endif
--
2.3.7
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