sched: Fix possible divide by zero in avg_atom() calculation
authorMateusz Guzik <mguzik@redhat.com>
Sat, 14 Jun 2014 13:00:09 +0000 (15:00 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 28 Jul 2014 15:00:07 +0000 (08:00 -0700)
commit4aba6e36347232a9e0cc2e9c8daf42a6bdcdad66
tree03c2e9855259825ef33630581d37047525378e31
parente6be7d3115436b2527c60973c901ec3a7c6afe15
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/sched/debug.c