From 22356f447ceb8d97a4885792e7d9e4607f712e1b Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Tue, 24 Sep 2013 18:29:11 -0700
Subject: [PATCH] mm: Place preemption point in do_mlockall() loop
There is a loop in do_mlockall() that lacks a preemption point, which
means that the following can happen on non-preemptible builds of the
kernel. Dave Jones reports:
"My fuzz tester keeps hitting this. Every instance shows the non-irq
stack came in from mlockall. I'm only seeing this on one box, but
that has more ram (8gb) than my other machines, which might explain
it.
INFO: rcu_preempt self-detected stall on CPU { 3} (t=6500 jiffies g=470344 c=470343 q=0)
sending NMI to all CPUs:
NMI backtrace for cpu 3
CPU: 3 PID: 29664 Comm: trinity-child2 Not tainted 3.11.0-rc1+ #32
Call Trace:
lru_add_drain_all+0x15/0x20
SyS_mlockall+0xa5/0x1a0
tracesys+0xdd/0xe2"
This commit addresses this problem by inserting the required preemption
point.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/mlock.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/mlock.c b/mm/mlock.c
index d63802663242..67ba6da7d0e3 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -736,6 +736,7 @@ static int do_mlockall(int flags)
/* Ignore errors */
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
+ cond_resched();
}
out:
return 0;
--
2.34.1