From 0b1d647a02c5a1b67d45287eeb6cb3b2219c41c3 Mon Sep 17 00:00:00 2001 From: Pavel Mironchik Date: Thu, 31 Aug 2006 21:27:47 -0700 Subject: [PATCH] [PATCH] dm: work around mempool_alloc, bio_alloc_bioset deadlocks This patch works around a complex dm-related deadlock/livelock down in the mempool allocator. Alasdair said: Several dm targets suffer from this. Mempools are not yet used correctly everywhere in device-mapper: they can get shared when devices are stacked, and some targets share them across multiple instances. I made fixing this one of the prerequisites for this patch: md-dm-reduce-stack-usage-with-stacked-block-devices.patch which in some cases makes people more likely to hit the problem. There's been some progress on this recently with (unfinished) dm-crypt patches at: http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/ (dm-crypt-move-io-to-workqueue.patch plus dependencies) and: I've no problems with a temporary workaround like that, but Milan Broz (a new Redhat developer in the Czech Republic) has started reviewing all the mempool usage in device-mapper so I'm expecting we'll soon have a proper fix for this associated problems. [He's back from holiday at the start of next week.] For now, this sad-but-safe little patch will allow the machine to recover. [akpm@osdl.org: rewrote changelog] Cc: Alasdair G Kergon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempool.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/mempool.c b/mm/mempool.c index fe6e05289c..ccd8cb8cd4 100644 --- a/mm/mempool.c +++ b/mm/mempool.c @@ -238,8 +238,13 @@ repeat_alloc: init_wait(&wait); prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE); smp_mb(); - if (!pool->curr_nr) - io_schedule(); + if (!pool->curr_nr) { + /* + * FIXME: this should be io_schedule(). The timeout is there + * as a workaround for some DM problems in 2.6.18. + */ + io_schedule_timeout(5*HZ); + } finish_wait(&pool->wait, &wait); goto repeat_alloc; -- 2.39.5