On Mon, 9 Feb 2015 13:10:04 -0500 (EST) Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > The function raid10_unplug tests the "from_schedule" variable. If the > variable is true, it offloads queued bios to a thread. If the variable is > false, it submits queued bios directly. > > The function io_schedule calls blk_flush_plug, that calls > blk_flush_plug_list with "from_schedule" set to false. Consequently, > raid10_unplug tries to submit the bios directly when being called from > io_schedule, and that results in this warning. > > Fix the bug by calling blk_schedule_flush_plug instead of blk_flush_plug > from io_schedule. > > WARNING: CPU: 0 PID: 2876 at kernel/sched/core.c:7326 > __might_sleep+0xae/0xc0() > md: using maximum available idle IO bandwidth (but not more than 200000 > KB/sec) for resync. > do not call blocking ops when !TASK_RUNNING; state=2 set at > [<ffffffff81232b10>] do_blockdev_direct_IO+0x11a0/0x2e50 > Modules linked in: loop dm_raid raid456 async_raid6_recov async_memcpy > async_pq async_xor async_tx raid1 raid10 xor raid6_pq nfsv4 nfs nfsd > auth_rpcgss oid_registry nfs_acl lockd grace sunrpc autofs4 fuse dm_crypt > md_mod uhci_hcd ehci_hcd usbcore i2c_piix4 serio_raw i2c_core virtio_net > usb_common floppy pvpanic evdev sym53c8xx dm_mirror dm_region_hash dm_log > dm_mod > md: using 128k window, over a total of 1024k. > CPU: 0 PID: 2876 Comm: lvm Not tainted 3.19.0-rc7-00195-gd4cecd5 #7 > Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > ffffffff819e4eba ffff88003c493818 ffffffff8163975d 0000000000000007 > ffff88003c493868 ffff88003c493858 ffffffff810587ba 00000000001d4280 > ffffffffa013b2b4 00000000000002e9 0000000000000000 ffff88003a8be010 > Call Trace: > [<ffffffff8163975d>] dump_stack+0x4f/0x7b > [<ffffffff810587ba>] warn_slowpath_common+0x8a/0xc0 > [<ffffffff81058836>] warn_slowpath_fmt+0x46/0x50 > [<ffffffff810af221>] ? __lock_acquire+0x411/0x1d10 > [<ffffffff81232b10>] ? do_blockdev_direct_IO+0x11a0/0x2e50 > [<ffffffff81232b10>] ? do_blockdev_direct_IO+0x11a0/0x2e50 > [<ffffffff810842ae>] __might_sleep+0xae/0xc0 > [<ffffffffa0131816>] md_super_wait+0x26/0x90 [md_mod] > [<ffffffffa0138903>] bitmap_unplug+0x193/0x1a0 [md_mod] > [<ffffffff8112ce33>] ? __delayacct_blkio_start+0x23/0x30 > [<ffffffffa00ee940>] raid10_unplug+0xe0/0x160 [raid10] > [<ffffffff8136d01a>] blk_flush_plug_list+0xaa/0x250 > [<ffffffff810aeafd>] ? trace_hardirqs_on+0xd/0x10 > [<ffffffff8163b602>] io_schedule+0x82/0x150 > [<ffffffff81232b3a>] do_blockdev_direct_IO+0x11ca/0x2e50 > [<ffffffff810914a5>] ? sched_clock_local+0x25/0x90 > [<ffffffff8122ed00>] ? I_BDEV+0x10/0x10 > [<ffffffff8123480c>] __blockdev_direct_IO+0x4c/0x50 > [<ffffffff8122ed00>] ? I_BDEV+0x10/0x10 > [<ffffffff8122f4ce>] blkdev_direct_IO+0x4e/0x50 > [<ffffffff8122ed00>] ? I_BDEV+0x10/0x10 > [<ffffffff8117a095>] generic_file_direct_write+0xb5/0x190 > [<ffffffff8117a455>] __generic_file_write_iter+0x2e5/0x390 > [<ffffffff8122f7ff>] blkdev_write_iter+0x2f/0xa0 > [<ffffffff811ece11>] new_sync_write+0x81/0xb0 > [<ffffffff811ed61a>] vfs_write+0xba/0x1f0 > [<ffffffff811ee269>] SyS_write+0x49/0xb0 > [<ffffffff81645063>] sysenter_dispatch+0x7/0x1f > [<ffffffff813a24db>] ? trace_hardirqs_on_thunk+0x3a/0x3f > ---[ end trace 28ea2673fb871796 ]--- > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Reported-by: Zdenek Kabelac <zkabelac@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx # 2.6.39+ > > --- > kernel/sched/core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > Index: linux-2.6/kernel/sched/core.c > =================================================================== > --- linux-2.6.orig/kernel/sched/core.c 2015-02-09 11:35:35.169156491 +0100 > +++ linux-2.6/kernel/sched/core.c 2015-02-09 12:11:35.140557980 +0100 > @@ -4397,7 +4397,7 @@ void __sched io_schedule(void) > > delayacct_blkio_start(); > atomic_inc(&rq->nr_iowait); > - blk_flush_plug(current); > + blk_schedule_flush_plug(current); > current->in_iowait = 1; > schedule(); > current->in_iowait = 0; > @@ -4413,7 +4413,7 @@ long __sched io_schedule_timeout(long ti > > delayacct_blkio_start(); > atomic_inc(&rq->nr_iowait); > - blk_flush_plug(current); > + blk_schedule_flush_plug(current); > current->in_iowait = 1; > ret = schedule_timeout(timeout); > current->in_iowait = 0; > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ Hi, I think the current code is correct, but that the warning is wrong. I believe it should be fixed by adding sched_annotate_sleep() to blk_flush_plug(). See the separate thread with subject RAID1 might_sleep() warning on 3.19-rc7 on linux-raid and lkml. Thanks, NeilBrown
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