Re: BUG: scheduling while atomic in blk_mq codepath?
From: Jens Axboe
Date: Thu Jun 19 2014 - 11:59:45 EST
On 2014-06-19 08:35, Theodore Ts'o wrote:
While trying to bisect some problems which were introduced sometime
between 3.15 and 3.16-rc1 (specifically, (1) reads to a block device
at offset 262144 * 4k are failing with a short read, and (2) block
device reads are sometimes causing the entire kernel to hang), the
following BUG got hit.
[ 0.000000] Linux version 3.15.0-rc8-06047-gaaeb255 (tytso@closure) (gcc version 4.8.3 (Debian 4.8.3-2) ) #1902 SMP Thu Jun 19 11:16:10 EDT 2014
[....] Checking file systems...fsck from util-linux 2.20.1
/dev/vdg was not cleanly unmounted, check forced.
[ 4.161703] BUG: scheduling while atomic: fsck.ext4/2072/0x0000000266.5%
[ 4.163673] no locks held by fsck.ext4/2072.
[ 4.164318] Modules linked in:
[ 4.164845] CPU: 0 PID: 2072 Comm: fsck.ext4 Not tainted 3.15.0-rc8-06047-gaaeb255 #1902
[ 4.166047] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 4.166917] 00000000 00000000 f52c5ba0 c0832655 f5158610 f52c5bac c082f88a f6501e40
[ 4.168188] f52c5c20 c08362ca c0eb3e40 c0eb3e40 374d3933 00000001 0396a8da 00000000
[ 4.169474] f5158610 f51f1674 f4f46a00 f52c5be4 c015dd4b f4f46a00 f52c5bf0 c015dd5e
[ 4.170781] Call Trace:
[ 4.171159] [<c0832655>] dump_stack+0x48/0x60
[ 4.171838] [<c082f88a>] __schedule_bug+0x5c/0x6d
[ 4.172572] [<c08362ca>] __schedule+0x61/0x65a
[ 4.173228] [<c015dd4b>] ? kvm_clock_read+0x1f/0x29
[ 4.173977] [<c015dd5e>] ? kvm_clock_get_cycles+0x9/0xc
[ 4.174771] [<c01b4cb9>] ? timekeeping_get_ns.constprop.14+0x10/0x56
[ 4.175701] [<c0836922>] schedule+0x5f/0x61
[ 4.176345] [<c0836aa2>] io_schedule+0x50/0x67
[ 4.177060] [<c0423b2d>] bt_get+0xaf/0xd1
[ 4.177677] [<c0198282>] ? wake_up_atomic_t+0x1f/0x1f
[ 4.178444] [<c0423bfd>] blk_mq_get_tag+0x26/0x82
[ 4.179158] [<c0420f14>] __blk_mq_alloc_request+0x2a/0x169
[ 4.180022] [<c04222b5>] blk_mq_map_request+0x137/0x1e3
[ 4.180825] [<c0422f89>] blk_sq_make_request+0x82/0x145
[ 4.181630] [<c041a687>] generic_make_request+0x82/0xb5
[ 4.182430] [<c041a7aa>] submit_bio+0xf0/0x109
[ 4.183113] [<c019e97c>] ? trace_hardirqs_on_caller+0x14e/0x169
[ 4.184019] [<c025de72>] _submit_bh+0x1ad/0x1ca
[ 4.184661] [<c025de9e>] submit_bh+0xf/0x11
[ 4.185267] [<c025f5c9>] block_read_full_page+0x1e2/0x1f2
[ 4.186073] [<c025f8cd>] ? I_BDEV+0xa/0xa
[ 4.186695] [<c020ad30>] ? __lru_cache_add+0x24/0x46
[ 4.187452] [<c020af13>] ? lru_cache_add+0xd/0xf
[ 4.188130] [<c025fc04>] blkdev_readpage+0x14/0x16
[ 4.188832] [<c0209adf>] __do_page_cache_readahead+0x1c0/0x1eb
[ 4.189704] [<c0209cb9>] ondemand_readahead+0x1af/0x1b9
[ 4.190508] [<c0209d22>] page_cache_async_readahead+0x5f/0x6a
[ 4.191424] [<c0202370>] generic_file_aio_read+0x226/0x4f4
[ 4.192272] [<c0260841>] blkdev_aio_read+0x90/0x9e
[ 4.193017] [<c02385cd>] do_sync_read+0x52/0x79
[ 4.193731] [<c023857b>] ? fdput_pos+0x25/0x25
[ 4.194412] [<c0238d27>] vfs_read+0x72/0xd1
[ 4.195064] [<c02391da>] SyS_read+0x49/0x7c
[ 4.195700] [<c083a0c9>] syscall_call+0x7/0xb
[ 4.196385] [<c0830000>] ? print_usage_bug+0xcd/0x18e
Is any of these known problems? This is blocking me from doing any
kind of testing at the moment... (these problems are showing up while
running KVM using virtio devices).
I believe you already reported this issue a while back, and it should be
fixed by commit cb96a42c in the kernel.
The other issue, not sure, not a lot of detail. It may be fixed by the
pull request I sent out yesterday. You can try pulling in:
git://git.kernel.dk/linux-block.git for-linus
and see if that fixes it for you.
--
Jens Axboe
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