* [PATCH] sched: fix possible divide by zero in avg_atom calculation
@ 2014-06-14 13:00 Mateusz Guzik
2014-07-07 12:44 ` Peter Zijlstra
2014-07-16 19:22 ` [tip:sched/urgent] sched: Fix possible divide by zero in avg_atom () calculation tip-bot for Mateusz Guzik
0 siblings, 2 replies; 3+ messages in thread
From: Mateusz Guzik @ 2014-06-14 13:00 UTC (permalink / raw)
To: linux-kernel; +Cc: Ingo Molnar, Peter Zijlstra, stable
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@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
---
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 695f977..627b3c3 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;
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] sched: fix possible divide by zero in avg_atom calculation
2014-06-14 13:00 [PATCH] sched: fix possible divide by zero in avg_atom calculation Mateusz Guzik
@ 2014-07-07 12:44 ` Peter Zijlstra
2014-07-16 19:22 ` [tip:sched/urgent] sched: Fix possible divide by zero in avg_atom () calculation tip-bot for Mateusz Guzik
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2014-07-07 12:44 UTC (permalink / raw)
To: Mateusz Guzik; +Cc: linux-kernel, Ingo Molnar, stable
[-- Attachment #1: Type: text/plain, Size: 517 bytes --]
On Sat, Jun 14, 2014 at 03:00:09PM +0200, Mateusz Guzik wrote:
> 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@redhat.com>
Thanks.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip:sched/urgent] sched: Fix possible divide by zero in avg_atom () calculation
2014-06-14 13:00 [PATCH] sched: fix possible divide by zero in avg_atom calculation Mateusz Guzik
2014-07-07 12:44 ` Peter Zijlstra
@ 2014-07-16 19:22 ` tip-bot for Mateusz Guzik
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Mateusz Guzik @ 2014-07-16 19:22 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, torvalds, peterz, mguzik, tglx
Commit-ID: b0ab99e7736af88b8ac1b7ae50ea287fffa2badc
Gitweb: http://git.kernel.org/tip/b0ab99e7736af88b8ac1b7ae50ea287fffa2badc
Author: Mateusz Guzik <mguzik@redhat.com>
AuthorDate: Sat, 14 Jun 2014 15:00:09 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 16 Jul 2014 13:36:07 +0200
sched: Fix possible divide by zero in avg_atom() calculation
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@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 695f977..627b3c3 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;
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2014-06-14 13:00 [PATCH] sched: fix possible divide by zero in avg_atom calculation Mateusz Guzik
2014-07-07 12:44 ` Peter Zijlstra
2014-07-16 19:22 ` [tip:sched/urgent] sched: Fix possible divide by zero in avg_atom () calculation tip-bot for Mateusz Guzik
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