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| author | Mateusz Guzik <mguzik@redhat.com> | 2014-06-14 15:00:09 +0200 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2014-08-06 18:07:38 +0100 |
| commit | 8f88141b2724459ab757b44a5251cd915169f5de (patch) | |
| tree | 49f45d8b09609bada3fef82d455c8f1eb22d7fe9 | |
| parent | 79e70e9dc0cb707ad58ce8d3ed75b50610581edd (diff) | |
| download | lwn-8f88141b2724459ab757b44a5251cd915169f5de.tar.gz lwn-8f88141b2724459ab757b44a5251cd915169f5de.zip | |
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@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.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>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | kernel/sched_debug.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index f4010e2820fc..704ffe30bbd7 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -467,7 +467,7 @@ 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; |