[3.13.y.z extended stable] Patch "sched: Fix possible divide by zero in avg_atom() calculation" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Wed Aug 6 20:54:56 UTC 2014
This is a note to let you know that I have just added a patch titled
sched: Fix possible divide by zero in avg_atom() calculation
to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue
This patch is scheduled to be released in version 3.13.11.6.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 4445f0fab96f24ca288902e0af8280879b1c099a Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mguzik at redhat.com>
Date: Sat, 14 Jun 2014 15:00:09 +0200
Subject: sched: Fix possible divide by zero in avg_atom() calculation
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 at redhat.com>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@redhat.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
kernel/sched/debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 5c34d18..0c60913 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
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;
--
1.9.1
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