This is a note to let you know that I've just added the patch titled
sched: Fix possible divide by zero in avg_atom() calculation
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fix-possible-divide-by-zero-in-avg_atom-calculation.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b0ab99e7736af88b8ac1b7ae50ea287fffa2badc Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mguzik@xxxxxxxxxx>
Date: Sat, 14 Jun 2014 15:00:09 +0200
Subject: sched: Fix possible divide by zero in avg_atom() calculation
From: Mateusz Guzik <mguzik@xxxxxxxxxx>
commit b0ab99e7736af88b8ac1b7ae50ea287fffa2badc upstream.
proc_sched_show_task() does:
if (nr_switches)
do_div(avg_atom, nr_switches);
nr_switches is unsigned long and do_div truncates it to 32 bits, which
means it can test non-zero on e.g. x86-64 and be truncated to zero for
division.
Fix the problem by using div64_ul() instead.
As a side effect calculations of avg_atom for big nr_switches are now correct.
Signed-off-by: Mateusz Guzik <mguzik@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_st
avg_atom = p->se.sum_exec_runtime;
if (nr_switches)
- do_div(avg_atom, nr_switches);
+ avg_atom = div64_ul(avg_atom, nr_switches);
else
avg_atom = -1LL;
Patches currently in stable-queue which might be from mguzik@xxxxxxxxxx are
queue-3.15/sched-fix-possible-divide-by-zero-in-avg_atom-calculation.patch
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