On Wed, 31 Mar 2010 09:41:24 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > With this fixed, the test for non-zero tsk->mm is't really needed in
> > do_exit(), is it? I guess it makes sense though - sync_mm_rss() only
> > really works for kernel threads by luck..
>
> At first, I considered so, too. But I changed my mind to show
> "we know tsk->mm can be NULL here!" by code.
> Because __sync_mm_rss_stat() has BUG_ON(!mm), the code reader will think
> tsk->mm shouldn't be NULL always.
>
> Doesn't make sense ?
uh, not really ;)
I think we should do this too:
--- a/mm/memory.c~exit-fix-oops-in-sync_mm_rss-fix
+++ a/mm/memory.c
@@ -131,7 +131,6 @@ static void __sync_task_rss_stat(struct
for (i = 0; i < NR_MM_COUNTERS; i++) {
if (task->rss_stat.count[i]) {
- BUG_ON(!mm);
add_mm_counter(mm, i, task->rss_stat.count[i]);
task->rss_stat.count[i] = 0;
}
_
Because we just made sure it can't happen, and if it _does_ happen, the
oops will tell us the samme thing that the BUG_ON() would have.
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