The patch titled
Subject: lib/flex_proportions.c: fix corruption of denominator in flexible
proportions
has been added to the -mm tree. Its filename is
lib-flex_proportionsc-fix-corruption-of-denominator-in-flexible-proportions.patch
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From: Jan Kara <[email protected]>
Subject: lib/flex_proportions.c: fix corruption of denominator in flexible
proportions
When racing with CPU hotplug, percpu_counter_sum() can return negative
values for the number of observed events. This confuses
fprop_new_period(), which uses unsigned type and as a result number of
events is set to big *positive* number. From that moment on, things go
pear shaped and can result e.g. in division by zero as denominator is
later truncated to 32-bits.
Fix the issue by using a signed type in fprop_new_period(). That makes us
bail out from the function without doing anything (mistakenly) thinking
there are no events to age. That makes aging somewhat inaccurate but
getting accurate data would be rather hard.
Signed-off-by: Jan Kara <[email protected]>
Reported-by: Borislav Petkov <[email protected]>
Reported-by: Srivatsa S. Bhat <[email protected]>
Cc: Wu Fengguang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
lib/flex_proportions.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN
lib/flex_proportions.c~lib-fix-corruption-of-denominator-in-flexible-proportions
lib/flex_proportions.c
---
a/lib/flex_proportions.c~lib-fix-corruption-of-denominator-in-flexible-proportions
+++ a/lib/flex_proportions.c
@@ -62,7 +62,7 @@ void fprop_global_destroy(struct fprop_g
*/
bool fprop_new_period(struct fprop_global *p, int periods)
{
- u64 events;
+ s64 events;
unsigned long flags;
local_irq_save(flags);
_
Patches currently in -mm which might be from [email protected] are
lib-flex_proportionsc-fix-corruption-of-denominator-in-flexible-proportions.patch
linux-next.patch
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