From 0eb69a0c584d0eaec6c2b6663e03184625c3517b Mon Sep 17 00:00:00 2001 From: Sebastian Ott Date: Thu, 5 Jun 2014 14:30:19 +0200 Subject: [PATCH] s390/airq: silence lockdep warning airq_iv_(alloc|free) is called by some users with interrupts enabled and by some with interrupts disabled which leads to the following lockdep warning: [ INFO: possible irq lock inversion dependency detected ] 3.14.0-15249-gbf29b7b-dirty #25 Not tainted --------------------------------------------------------- insmod/2108 just changed the state of lock: (&(&iv->lock)->rlock){+.....}, at: [<000000000046ee3e>] airq_iv_alloc+0x62/0x228 but this lock was taken by another, HARDIRQ-READ-safe lock in the past: (&info->lock){.-.-..} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&iv->lock)->rlock); local_irq_disable(); lock(&info->lock); lock(&(&iv->lock)->rlock); lock(&info->lock); *** DEADLOCK *** Although this is a false alarm (since each airq user consistently calls these functions from the same context) fix this by ensuring that interrupts are disabled when the airq lock is held. Reported-by: Frank Blaschka Signed-off-by: Sebastian Ott Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/airq.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c index 445564c790f6..00bfbee0af9e 100644 --- a/drivers/s390/cio/airq.c +++ b/drivers/s390/cio/airq.c @@ -196,11 +196,11 @@ EXPORT_SYMBOL(airq_iv_release); */ unsigned long airq_iv_alloc(struct airq_iv *iv, unsigned long num) { - unsigned long bit, i; + unsigned long bit, i, flags; if (!iv->avail || num == 0) return -1UL; - spin_lock(&iv->lock); + spin_lock_irqsave(&iv->lock, flags); bit = find_first_bit_inv(iv->avail, iv->bits); while (bit + num <= iv->bits) { for (i = 1; i < num; i++) @@ -218,9 +218,8 @@ unsigned long airq_iv_alloc(struct airq_iv *iv, unsigned long num) } if (bit + num > iv->bits) bit = -1UL; - spin_unlock(&iv->lock); + spin_unlock_irqrestore(&iv->lock, flags); return bit; - } EXPORT_SYMBOL(airq_iv_alloc); @@ -232,11 +231,11 @@ EXPORT_SYMBOL(airq_iv_alloc); */ void airq_iv_free(struct airq_iv *iv, unsigned long bit, unsigned long num) { - unsigned long i; + unsigned long i, flags; if (!iv->avail || num == 0) return; - spin_lock(&iv->lock); + spin_lock_irqsave(&iv->lock, flags); for (i = 0; i < num; i++) { /* Clear (possibly left over) interrupt bit */ clear_bit_inv(bit + i, iv->vector); @@ -248,7 +247,7 @@ void airq_iv_free(struct airq_iv *iv, unsigned long bit, unsigned long num) while (iv->end > 0 && !test_bit_inv(iv->end - 1, iv->avail)) iv->end--; } - spin_unlock(&iv->lock); + spin_unlock_irqrestore(&iv->lock, flags); } EXPORT_SYMBOL(airq_iv_free); -- 2.30.2