From f01eb3640308c005d31b29d0a8bc2b7acb4e3f75 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 12 Dec 2009 14:46:33 -0800
Subject: [PATCH] [BKL] add 'might_sleep()' to the outermost lock taker
As shown by the previous patch (6698e3472: "tty: Fix BKL taken under a
spinlock bug introduced in the BKL split") the BKL removal is prone to
some subtle issues, where removing the BKL in one place may in fact make
a previously nested BKL call the new outer call, and then prone to nasty
deadlocks with other spinlocks.
In general, we should never take the BKL while we're holding a spinlock,
so let's just add a "might_sleep()" to it (even though the BKL doesn't
technically sleep - at least not yet), and we'll get nice warnings the
next time this kind of problem happens during BKL removal.
Acked-and-Tested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
lib/kernel_lock.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/lib/kernel_lock.c b/lib/kernel_lock.c
index 4ebfa5a164d7..5526b46aba94 100644
--- a/lib/kernel_lock.c
+++ b/lib/kernel_lock.c
@@ -122,8 +122,10 @@ void __lockfunc _lock_kernel(const char *func, const char *file, int line)
trace_lock_kernel(func, file, line);
- if (likely(!depth))
+ if (likely(!depth)) {
+ might_sleep();
__lock_kernel();
+ }
current->lock_depth = depth;
}
--
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