From 708edafa883186f55b24fa0c380242b5282f9105 Mon Sep 17 00:00:00 2001 From: John Garry Date: Thu, 14 Nov 2019 01:27:22 +0800 Subject: sbitmap: Delete sbitmap_any_bit_clear() Since the only caller of this function has been deleted, delete this one also. Signed-off-by: John Garry Signed-off-by: Jens Axboe --- lib/sbitmap.c | 17 ----------------- 1 file changed, 17 deletions(-) (limited to 'lib/sbitmap.c') diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 969e5400a615..33feec8989f1 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -236,23 +236,6 @@ bool sbitmap_any_bit_set(const struct sbitmap *sb) } EXPORT_SYMBOL_GPL(sbitmap_any_bit_set); -bool sbitmap_any_bit_clear(const struct sbitmap *sb) -{ - unsigned int i; - - for (i = 0; i < sb->map_nr; i++) { - const struct sbitmap_word *word = &sb->map[i]; - unsigned long mask = word->word & ~word->cleared; - unsigned long ret; - - ret = find_first_zero_bit(&mask, word->depth); - if (ret < word->depth) - return true; - } - return false; -} -EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear); - static unsigned int __sbitmap_weight(const struct sbitmap *sb, bool set) { unsigned int i, weight = 0; -- cgit v1.2.3 From df034c93f15ee71df231ff9fe311d27ff08a2a52 Mon Sep 17 00:00:00 2001 From: David Jeffery Date: Tue, 17 Dec 2019 11:00:24 -0500 Subject: sbitmap: only queue kyber's wait callback if not already active Under heavy loads where the kyber I/O scheduler hits the token limits for its scheduling domains, kyber can become stuck. When active requests complete, kyber may not be woken up leaving the I/O requests in kyber stuck. This stuck state is due to a race condition with kyber and the sbitmap functions it uses to run a callback when enough requests have completed. The running of a sbt_wait callback can race with the attempt to insert the sbt_wait. Since sbitmap_del_wait_queue removes the sbt_wait from the list first then sets the sbq field to NULL, kyber can see the item as not on a list but the call to sbitmap_add_wait_queue will see sbq as non-NULL. This results in the sbt_wait being inserted onto the wait list but ws_active doesn't get incremented. So the sbitmap queue does not know there is a waiter on a wait list. Since sbitmap doesn't think there is a waiter, kyber may never be informed that there are domain tokens available and the I/O never advances. With the sbt_wait on a wait list, kyber believes it has an active waiter so cannot insert a new waiter when reaching the domain's full state. This race can be fixed by only adding the sbt_wait to the queue if the sbq field is NULL. If sbq is not NULL, there is already an action active which will trigger the re-running of kyber. Let it run and add the sbt_wait to the wait list if still needing to wait. Reviewed-by: Omar Sandoval Signed-off-by: David Jeffery Reported-by: John Pittman Tested-by: John Pittman Signed-off-by: Jens Axboe --- lib/sbitmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib/sbitmap.c') diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 33feec8989f1..af88d1346dd7 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -650,8 +650,8 @@ void sbitmap_add_wait_queue(struct sbitmap_queue *sbq, if (!sbq_wait->sbq) { sbq_wait->sbq = sbq; atomic_inc(&sbq->ws_active); + add_wait_queue(&ws->wait, &sbq_wait->wait); } - add_wait_queue(&ws->wait, &sbq_wait->wait); } EXPORT_SYMBOL_GPL(sbitmap_add_wait_queue); -- cgit v1.2.3