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commit 3719876809e745b9db5293d418600c194bbf5c23
parent c962cb323ec260652cff9331e7bf3d606292db88
Author: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date:   Mon, 14 Jan 2019 12:25:40 -0500

sbitmap: Protect swap_lock from softirqs

The swap_lock used by sbitmap has a chain with locks taken from softirq,
but the swap_lock is not protected from being preempted by softirqs.

A chain exists of:

 sbq->ws[i].wait -> dispatch_wait_lock -> swap_lock

Where the sbq->ws[i].wait lock can be taken from softirq context, which
means all locks below it in the chain must also be protected from
softirqs.

Reported-by: Clark Williams <williams@redhat.com>
Fixes: 58ab5e32e6fd ("sbitmap: silence bogus lockdep IRQ warning")
Fixes: ea86ea2cdced ("sbitmap: amortize cost of clearing bits")
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Diffstat:
Mlib/sbitmap.c | 12++----------
1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c @@ -26,14 +26,9 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index) { unsigned long mask, val; - unsigned long __maybe_unused flags; bool ret = false; - /* Silence bogus lockdep warning */ -#if defined(CONFIG_LOCKDEP) - local_irq_save(flags); -#endif - spin_lock(&sb->map[index].swap_lock); + spin_lock_bh(&sb->map[index].swap_lock); if (!sb->map[index].cleared) goto out_unlock; @@ -54,10 +49,7 @@ static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index) ret = true; out_unlock: - spin_unlock(&sb->map[index].swap_lock); -#if defined(CONFIG_LOCKDEP) - local_irq_restore(flags); -#endif + spin_unlock_bh(&sb->map[index].swap_lock); return ret; }