From 22356f447ceb8d97a4885792e7d9e4607f712e1b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" 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 Signed-off-by: Paul E. McKenney Cc: KOSAKI Motohiro Cc: Michel Lespinasse Cc: Andrew Morton Signed-off-by: Linus Torvalds --- 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; -- 2.30.2