From 8cf466602028196b939255f1eb4e9817efd1db6d Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Wed, 11 Oct 2017 10:39:15 -0700 Subject: [PATCH] kyber: fix hang on domain token wait queue When we're getting a domain token, if we fail to get a token on our first attempt, we put the current hardware queue on a wait queue and then try again just in case a token was freed after our initial attempt but before we got on the wait queue. If this second attempt succeeds, we currently leave the hardware queue on the wait queue. Usually this is okay; we'll just run the hardware queue one extra time when another token is freed. However, if the hardware queue doesn't have any other requests waiting, then when it it gets the extra wakeup, it won't have anything to free and therefore won't wake up any other hardware queues. If tokens are limited, then we won't make forward progress and the device will hang. Reported-by: Bin Zha Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- block/kyber-iosched.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c index f58cab82105b..db5bfc6342d3 100644 --- a/block/kyber-iosched.c +++ b/block/kyber-iosched.c @@ -541,9 +541,17 @@ static int kyber_get_domain_token(struct kyber_queue_data *kqd, /* * Try again in case a token was freed before we got on the wait - * queue. + * queue. The waker may have already removed the entry from the + * wait queue, but list_del_init() is okay with that. */ nr = __sbitmap_queue_get(domain_tokens); + if (nr >= 0) { + unsigned long flags; + + spin_lock_irqsave(&ws->wait.lock, flags); + list_del_init(&wait->entry); + spin_unlock_irqrestore(&ws->wait.lock, flags); + } } return nr; } -- 2.30.2