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Commit 37198768 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware) Committed by Linus Torvalds
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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: default avatarClark Williams <williams@redhat.com>
Fixes: 58ab5e32 ("sbitmap: silence bogus lockdep IRQ warning")
Fixes: ea86ea2c ("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: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c962cb32

lib/sbitmap.c

+2 −10
Original line number Diff line number Diff line
@@ -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;

}