[PATCH 09/12] oom: remove PF_EXITING check completely

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Currently, PF_EXITING check is completely broken. because 1) It only
care main-thread and ignore sub-threads 2) If user enable core-dump
feature, it can makes deadlock because the task during coredump ignore
SIGKILL.

The deadlock is certenaly worst result, then, minor PF_EXITING
optimization worth is relatively ignorable.

This patch removes it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
---
 mm/oom_kill.c |   27 ---------------------------
 1 files changed, 0 insertions(+), 27 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 6360c56..5d723fb 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -302,24 +302,6 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
 		if (test_tsk_thread_flag(p, TIF_MEMDIE))
 			return ERR_PTR(-1UL);
 
-		/*
-		 * This is in the process of releasing memory so wait for it
-		 * to finish before killing some other task by mistake.
-		 *
-		 * However, if p is the current task, we allow the 'kill' to
-		 * go ahead if it is exiting: this will simply set TIF_MEMDIE,
-		 * which will allow it to gain access to memory reserves in
-		 * the process of exiting and releasing its resources.
-		 * Otherwise we could get an easy OOM deadlock.
-		 */
-		if (p->flags & PF_EXITING) {
-			if (p != current)
-				return ERR_PTR(-1UL);
-
-			chosen = p;
-			*ppoints = ULONG_MAX;
-		}
-
 		points = badness(p, uptime.tv_sec);
 		if (points > *ppoints || !chosen) {
 			chosen = p;
@@ -444,15 +426,6 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
 	if (printk_ratelimit())
 		dump_header(p, gfp_mask, order, mem);
 
-	/*
-	 * If the task is already exiting, don't alarm the sysadmin or kill
-	 * its children or threads, just set TIF_MEMDIE so it can die quickly
-	 */
-	if (p->flags & PF_EXITING) {
-		__oom_kill_process(p, mem, 0);
-		return 0;
-	}
-
 	printk(KERN_ERR "%s: kill process %d (%s) score %li or a child\n",
 					message, task_pid_nr(p), p->comm, points);
 
-- 
1.6.5.2