From 2844dc32ea67044b345221067207ce67ffe8da76 Mon Sep 17 00:00:00 2001 From: hui jiao Date: Thu, 5 Jun 2014 11:34:24 +0800 Subject: [PATCH] md/raid5: deadlock between retry_aligned_read with barrier io A chunk aligned read increases counter active_aligned_reads and decreases it after sub-device handle it successfully. But when a read error occurs, the read redispatched by raid5d, and the active_aligned_reads will not be decreased until we can grab a stripe head in retry_aligned_read. Now suppose, a barrier io comes, set conf->quiesce to 2, and wait until both active_stripes and active_aligned_reads are zero. The retried chunk aligned read gets stuck at get_active_stripe waiting until conf->quiesce becomes 0. Retry_aligned_read and barrier io are waiting each other now. One possible solution is that we ignore conf->quiesce, let the retried aligned read finish. I reproduced this deadlock and test this patch on centos6.0 Signed-off-by: NeilBrown --- drivers/md/raid5.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index d69fd9888c2c..ce421e3a3980 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -5115,7 +5115,7 @@ static int retry_aligned_read(struct r5conf *conf, struct bio *raid_bio) /* already done this stripe */ continue; - sh = get_active_stripe(conf, sector, 0, 1, 0); + sh = get_active_stripe(conf, sector, 0, 1, 1); if (!sh) { /* failed to get a stripe - must wait */