[PATCH 1/3] oom: oom_kill_task: mark every thread as TIF_MEMDIE

[Oleg Nesterov <oleg@redhat.com>]

oom_kill_task() kills the whole thread group, but only one task gets
TIF_MEMDIE. This can't be right, every test_thread_flag(TIF_MEMDIE)
check is per-thread.

I think it should be replaced by MMF_, but as a first step let's change
oom_kill_task() to mark every sub-thread as TIF_MEMDIE. And change the
"Kill all processes sharing p->mm" code the same way.

This also fixes another problem. sysctl_oom_kill_allocating_task case
does oom_kill_process(current). If current is not the main thread, then
select_bad_process() won't see the TIF_MEMDIE task.

Note:

	- oom_kill_task()->for_each_process() is wrong. It can't detect
	  all processes sharing p->mm. The fix is simple

	- This patch doesn't change other callers of set_*(TIF_MEMDIE).
	  This needs a separate discussion, but oom_kill_process() is
	  simply wrong.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 mm/oom_kill.c |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

--- 38/mm/oom_kill.c~oom_kill_spread_memdie	2011-03-12 14:19:36.000000000 +0100
+++ 38/mm/oom_kill.c	2011-03-12 14:20:42.000000000 +0100
@@ -401,6 +401,18 @@ static void dump_header(struct task_stru
 		dump_tasks(mem, nodemask);
 }
 
+static void do_oom_kill(struct task_struct *p)
+{
+	struct task_struct *t;
+
+	t = p;
+	do {
+		set_tsk_thread_flag(t, TIF_MEMDIE);
+	} while_each_thread(p, t);
+
+	force_sig(SIGKILL, p);
+}
+
 #define K(x) ((x) << (PAGE_SHIFT-10))
 static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
 {
@@ -436,12 +448,10 @@ static int oom_kill_task(struct task_str
 			pr_err("Kill process %d (%s) sharing same memory\n",
 				task_pid_nr(q), q->comm);
 			task_unlock(q);
-			force_sig(SIGKILL, q);
+			do_oom_kill(q);
 		}
 
-	set_tsk_thread_flag(p, TIF_MEMDIE);
-	force_sig(SIGKILL, p);
-
+	do_oom_kill(p);
 	/*
 	 * We give our sacrificial lamb high priority and access to
 	 * all the memory it needs. That way it should be able to

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>