Re: divide error: bdi_dirty_limit+0x5a/0x9e
From: Conny Seidel <hidden>
Date: 2012-09-25 08:57:23
Also in:
lkml
* Jan Kara [off-list ref]:
[...]
The patch works for me. Tested it a couple of times on several machines without triggering the issue. Thanks for the fix.
From 1fd707552a67adf869958e479910d2f70452351b Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@suse.cz> Date: Mon, 24 Sep 2012 16:17:16 +0200 Subject: [PATCH] lib: 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. Reported-by: Borislav Petkov <redacted> Reported-by: Srivatsa S. Bhat <redacted> Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Conny Seidel <redacted>
quoted hunk ↗ jump to hunk
--- lib/flex_proportions.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c index c785554..ebf3bac 100644 --- a/lib/flex_proportions.c +++ b/lib/flex_proportions.c@@ -62,7 +62,7 @@ void fprop_global_destroy(struct fprop_global *p) */ bool fprop_new_period(struct fprop_global *p, int periods) { - u64 events; + s64 events; unsigned long flags; local_irq_save(flags); --1.7.1
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