It doesn't make sense to call thread_group_cputime() under task_lock(),
we can drop this lock right after we read get_mm_rss() and save the
value in the local variable.
Note: probably it makes more sense to use sum_exec_runtime instead
of utime + stime, it is much more precise. A task can eat a lot of
CPU time, but its Xtime can be zero.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
mm/oom_kill.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- MM/mm/oom_kill.c~4_FORKBOMB_DROP_TASK_LOCK_EARLIER 2010-04-02 19:55:46.000000000 +0200
+++ MM/mm/oom_kill.c 2010-04-02 20:16:13.000000000 +0200
@@ -110,13 +110,16 @@ static unsigned long oom_forkbomb_penalt
return 0;
list_for_each_entry(child, &tsk->children, sibling) {
struct task_cputime task_time;
- unsigned long runtime;
+ unsigned long runtime, rss;
task_lock(child);
if (!child->mm || child->mm == tsk->mm) {
task_unlock(child);
continue;
}
+ rss = get_mm_rss(child->mm);
+ task_unlock(child);
+
thread_group_cputime(child, &task_time);
runtime = cputime_to_jiffies(task_time.utime) +
cputime_to_jiffies(task_time.stime);
@@ -126,10 +129,9 @@ static unsigned long oom_forkbomb_penalt
* get to execute at all in such cases anyway.
*/
if (runtime < HZ) {
- child_rss += get_mm_rss(child->mm);
+ child_rss += rss;
forkcount++;
}
- task_unlock(child);
}
/*
--
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