[PATCH] select_bad_process(): kill a bogus PF_DEAD/TASK_DEAD check

The only one usage of TASK_DEAD outside of last schedule path,

select_bad_process:

	for_each_task(p) {

		if (!p->mm)
			continue;
		...
			if (p->state == TASK_DEAD)
				continue;
		...

TASK_DEAD state is set at the end of do_exit(), this means that p->mm
was already set == NULL by exit_mm(), so this task was already rejected
by 'if (!p->mm)' above.

Note also that the caller holds tasklist_lock, this means that p can't
pass exit_notify() and then set TASK_DEAD when p->mm != NULL.

Also, remove open-coded is_init().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 21f0a7e8e51491939b6f52c2bc227307790cf9a0..423dcae323a54cee90817df40cf4fdcf26b1b1dd 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -206,11 +206,14 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
                unsigned long points;
                int releasing;
 
-               /* skip kernel threads */
+               /*
+                * skip kernel threads and tasks which have already released
+                * their mm.
+                */
                if (!p->mm)
                        continue;
-               /* skip the init task with pid == 1 */
-               if (p->pid == 1)
+               /* skip the init task */
+               if (is_init(p))
                        continue;
 
                /*
@@ -226,9 +229,6 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
                releasing = test_tsk_thread_flag(p, TIF_MEMDIE) ||
                                                p->flags & PF_EXITING;
                if (releasing) {
-                       /* TASK_DEAD tasks have already released their mm */
-                       if (p->state == TASK_DEAD)
-                               continue;
                        if (p->flags & PF_EXITING && p == current) {
                                chosen = p;
                                *ppoints = ULONG_MAX;