On Sat, 24 Nov 2012 10:18:44 +0100 Torsten Kaiser <just.for.lkml@xxxxxxxxxxxxxx> wrote: > After my system got stuck with 3.7.0-rc2 as reported in > http://marc.info/?l=linux-kernel&m=135142236520624 LOCKDEP seem to > blame XFS, because it found 2 possible deadlocks. But after these > locking issues where fixed, my system got stuck again with 3.7.0-rc6 > as reported in http://marc.info/?l=linux-kernel&m=135344072325490 > Dave Chinner thinks its an issue within md, that it gets stuck and > that will then prevent any further xfs activity, and that I should > report it to the raid mailing list. > > The issue seems to be that multiple processes (kswapd0, xfsaild/md4 > and flush-9:4) get stuck in md_super_wait() like this: > [<ffffffff816b1224>] schedule+0x24/0x60 > [<ffffffff814f9dad>] md_super_wait+0x4d/0x80 > [<ffffffff8105ca30>] ? __init_waitqueue_head+0x60/0x60 > [<ffffffff81500753>] bitmap_unplug+0x173/0x180 > [<ffffffff810b6acf>] ? write_cache_pages+0x12f/0x420 > [<ffffffff810b6700>] ? set_page_dirty_lock+0x60/0x60 > [<ffffffff814e8eb8>] raid1_unplug+0x98/0x110 > [<ffffffff81278a6d>] blk_flush_plug_list+0xad/0x240 > [<ffffffff81278c13>] blk_finish_plug+0x13/0x50 > > The full hung-tasks stack traces and the output from SysRq+W can be > found at http://marc.info/?l=linux-kernel&m=135344072325490 or in the > LKML thread 'Hang in XFS reclaim on 3.7.0-rc3'. Yes, it does look like an md bug.... Can you test to see if this fixes it? diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 636bae0..a0f7309 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -963,7 +963,7 @@ static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule) struct r1conf *conf = mddev->private; struct bio *bio; - if (from_schedule) { + if (from_schedule || current->bio_list) { spin_lock_irq(&conf->device_lock); bio_list_merge(&conf->pending_bio_list, &plug->pending); conf->pending_count += plug->pending_cnt; > > I tried to understand how this could happen, but I don't see anything > wrong. Only that md_super_wait() looks like an open coded version of > __wait_event() and could be replaced by using it. yeah. md_super_wait was much more complex back when we had to support barrier operations. When they were removed it was simplified a lot and as you say it could be simplifier further. Patches welcome. > > http://marc.info/?l=linux-raid&m=135283030027665 looks like the same > issue, but using ext4 instead of xfs. yes, sure does. > > My setup wrt. md is two normal sata disks on a normal ahci controller > (AMD SB850 southbridge). > Both disks are divided into 4 partitions and each one assembled into a > separate raid1. > One (md5) is used for swap, the others hold xfs filesystems for /boot/ > (md4), / (md6) and /home/ (md7). > > I will try to provide any information you ask, but I can't reproduce > the hang on demand so gathering more information about that state is > not so easy, but I will try. I'm fairly confident the above patch will fixes it, and in any case it fixes a real bug. So if you could just run with it and confirm in a week or so that the problem hasn't recurred, that might have to do. Thanks, NeilBrown
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