[PATCH 13/12] oom: dump_header() need tasklist_lock

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

> (off-topic)
> 
> out_of_memory() calls dump_header()->dump_tasks() lockless, we
> need tasklist.

Makes perfectly sense. Thank you!


================================================================
Commit 1b604d75(oom: dump stack and VM state when oom killer panics)
added dump_header() call to three places. But It forgot to add
the tasklist_lock. Now, dump_header() is called without the lock.
It is obviously inadequate.

This patch fixes it.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
 mm/oom_kill.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index ad85e1b..2678a04 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -600,8 +600,8 @@ retry:
 
 	/* Found nothing?!?! Either we hang forever, or we panic. */
 	if (!p) {
-		read_unlock(&tasklist_lock);
 		dump_header(NULL, gfp_mask, order, NULL);
+		read_unlock(&tasklist_lock);
 		panic("Out of memory and no killable processes...\n");
 	}
 
@@ -633,7 +633,9 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 		return;
 
 	if (sysctl_panic_on_oom == 2) {
+		read_lock(&tasklist_lock);
 		dump_header(NULL, gfp_mask, order, NULL);
+		read_unlock(&tasklist_lock);
 		panic("out of memory. Compulsory panic_on_oom is selected.\n");
 	}
 
@@ -664,6 +666,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 	case CONSTRAINT_NONE:
 		if (sysctl_panic_on_oom) {
 			dump_header(NULL, gfp_mask, order, NULL);
+			read_unlock(&tasklist_lock);
 			panic("out of memory. panic_on_oom is selected\n");
 		}
 		/* Fall-through */
-- 
1.6.5.2





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