Commit b0ab99e7 authored by Mateusz Guzik's avatar Mateusz Guzik Committed by Ingo Molnar

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: default avatarMateusz Guzik <mguzik@redhat.com>
Signed-off-by: default avatarPeter 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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b6220ad6
...@@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) ...@@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
avg_atom = p->se.sum_exec_runtime; avg_atom = p->se.sum_exec_runtime;
if (nr_switches) if (nr_switches)
do_div(avg_atom, nr_switches); avg_atom = div64_ul(avg_atom, nr_switches);
else else
avg_atom = -1LL; avg_atom = -1LL;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment