Commit 4f419eb1 authored Jul 23, 2019 by Halil Pasic Committed by Heiko Carstens Jul 26, 2019

virtio/s390: fix race on airq_areas[]



The access to airq_areas was racy ever since the adapter interrupts got
introduced to virtio-ccw, but since commit 39c7dcb1 ("virtio/s390:
make airq summary indicators DMA") this became an issue in practice as
well. Namely before that commit the airq_info that got overwritten was
still functional. After that commit however the two infos share a
summary_indicator, which aggravates the situation. Which means
auto-online mechanism occasionally hangs the boot with virtio_blk.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 96b14536 ("virtio-ccw: virtio-ccw adapter interrupt support.")
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

parent 1a2dcff8

drivers/s390/virtio/virtio_ccw.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -145,6 +145,8 @@ struct airq_info {
		struct airq_iv *aiv;
		};
		static struct airq_info *airq_areas[MAX_AIRQ_AREAS];
		static DEFINE_MUTEX(airq_areas_lock);

		static u8 *summary_indicators;

		static inline u8 get_summary_indicator(struct airq_info info)
		@@ -265,9 +267,11 @@ static unsigned long get_airq_indicator(struct virtqueue *vqs[], int nvqs,
		unsigned long bit, flags;

		for (i = 0; i < MAX_AIRQ_AREAS && !indicator_addr; i++) {
		mutex_lock(&airq_areas_lock);
		if (!airq_areas[i])
		airq_areas[i] = new_airq_info(i);
		info = airq_areas[i];
		mutex_unlock(&airq_areas_lock);
		if (!info)
		return 0;
		write_lock_irqsave(&info->lock, flags);