On Mon, Mar 29, 2010 at 01:01:58PM -0700, David Rientjes wrote: > On Mon, 29 Mar 2010, anfei wrote: > > > I think this method is okay, but it's easy to trigger another bug of > > oom. See select_bad_process(): > > if (!p->mm) > > continue; > > !p->mm is not always an unaccepted condition. e.g. "p" is killed and > > doing exit, setting tsk->mm to NULL is before releasing the memory. > > And in multi threading environment, this happens much more. > > In __out_of_memory(), it panics if select_bad_process returns NULL. > > The simple way to fix it is as mem_cgroup_out_of_memory() does. > > > > This is fixed by > oom-avoid-race-for-oom-killed-tasks-detaching-mm-prior-to-exit.patch in > the -mm tree. > > See > http://userweb.kernel.org/~akpm/mmotm/broken-out/oom-avoid-race-for-oom-killed-tasks-detaching-mm-prior-to-exit.patch > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > index afeab2a..9aae208 100644 > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -588,12 +588,8 @@ retry: > > if (PTR_ERR(p) == -1UL) > > return; > > > > - /* Found nothing?!?! Either we hang forever, or we panic. */ > > - if (!p) { > > - read_unlock(&tasklist_lock); > > - dump_header(NULL, gfp_mask, order, NULL); > > - panic("Out of memory and no killable processes...\n"); > > - } > > + if (!p) > > + p = current; > > > > if (oom_kill_process(p, gfp_mask, order, points, NULL, > > "Out of memory")) > > The reason p wasn't selected is because it fails to meet the criteria for > candidacy in select_bad_process(), not necessarily because of a race with > the !p->mm check that the -mm patch cited above fixes. It's quite > possible that current has an oom_adj value of OOM_DISABLE, for example, > where this would be wrong. I see. And what about changing mem_cgroup_out_of_memory() too? diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 0cb1ca4..9e89a29 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -510,8 +510,10 @@ retry: if (PTR_ERR(p) == -1UL) goto out; - if (!p) - p = current; + if (!p) { + read_unlock(&tasklist_lock); + panic("Out of memory and no killable processes...\n"); + } if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, "Memory cgroup out of memory")) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>