For avoiding to trigger io timeout when one hctx becomes inactive, we
drain IOs when all CPUs of one hctx are offline. However, driver's
timeout handler may require cpus_read_lock, such as nvme-pci,
pci_alloc_irq_vectors_affinity() is called in nvme-pci reset context,
and irq_build_affinity_masks() needs cpus_read_lock().
Meantime when blk-mq's cpuhp offline handler is called, cpus_write_lock
is held, so deadlock is caused.
Fixes the issue by breaking the wait loop if enough long time elapses,
and these in-flight not drained IO still can be handled by timeout
handler.
Cc: linux-nvme@xxxxxxxxxxxxxxxxxxx
Reported-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Fixes: bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline")
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-mq.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c96c8c4f751b..4585985b8537 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3301,6 +3301,7 @@ static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu,
return true;
}
+#define BLK_MQ_MAX_OFFLINE_WAIT_MSECS 3000
static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
{
struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
@@ -3326,8 +3327,13 @@ static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
* frozen and there are no requests.
*/
if (percpu_ref_tryget(&hctx->queue->q_usage_counter)) {
- while (blk_mq_hctx_has_requests(hctx))
+ unsigned int wait_ms = 0;
+
+ while (blk_mq_hctx_has_requests(hctx) && wait_ms <
+ BLK_MQ_MAX_OFFLINE_WAIT_MSECS) {
msleep(5);
+ wait_ms += 5;
+ }
percpu_ref_put(&hctx->queue->q_usage_counter);
}
--
2.31.1
