Messages in this thread | | | Date | Mon, 28 Aug 2006 12:44:59 +0200 | From | Nick Piggin <> | Subject | Re: [PATCH -mm] select_bad_process: cleanup 'releasing' check |
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On Sun, Aug 27, 2006 at 10:25:38PM +0400, Oleg Nesterov wrote: > On top of "select_bad_process: kill a bogus PF_DEAD/TASK_DEAD check" > > No logic changes, but imho easier to read. > > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> > > --- 2.6.18-rc4/mm/oom_kill.c~ 2006-08-27 20:56:23.000000000 +0400 > +++ 2.6.18-rc4/mm/oom_kill.c 2006-08-27 21:58:32.000000000 +0400 > @@ -205,7 +205,6 @@ static struct task_struct *select_bad_pr > do_posix_clock_monotonic_gettime(&uptime); > do_each_thread(g, p) { > unsigned long points; > - int releasing; > > /* > * skip kernel threads and tasks which have already released > @@ -227,16 +226,15 @@ static struct task_struct *select_bad_pr > * the process of exiting and releasing its resources. > * Otherwise we could get an OOM deadlock. > */ > - releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || > - p->flags & PF_EXITING; > - if (releasing) { > - if (p->flags & PF_EXITING && p == current) { > - chosen = p; > - *ppoints = ULONG_MAX; > - break; > - } > - return ERR_PTR(-1UL); > - } > + if ((p->flags & PF_EXITING) && p == current) { > + chosen = p; > + *ppoints = ULONG_MAX; > + break; > + } > + if ((p->flags & PF_EXITING) || > + test_tsk_thread_flag(p, TIF_MEMDIE)) > + return ERR_PTR(-1UL); > +
Hmm, actually I think I spot a bug in the original logic: we don't want to have more than 1 task with TIF_MEMDIE at once, becaues that gives it access to memory reserves (but I saw it first in the new formulation, so maybe that does suggest it is more readable ;)
What I think should be done is the check for TIF_MEMDIE (and return -1) first, and then the PF_EXITING test. At which point, if current is found to be exiting, it should be chosen but not break... that way a subsequent MEMDIE or EXITING task has the chance to trigger the -1 return.
Anyway, if you don't want to do all that, I will when my hand gets better. Otherwise the 3 patches you sent look good, they could all have an
Acked-by: Nick Piggin <npiggin@suse.de>
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