lkml.org 
[lkml]   [2019]   [Aug]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH] loop: set PF_MEMALLOC_NOIO for the worker thread
    A deadlock with this stacktrace was observed.

    The loop thread does a GFP_KERNEL allocation, it calls into dm-bufio
    shrinker and the shrinker depends on I/O completion in the dm-bufio
    subsystem.

    In order to fix the deadlock (and other similar ones), we set the flag
    PF_MEMALLOC_NOIO at loop thread entry.

    PID: 474 TASK: ffff8813e11f4600 CPU: 10 COMMAND: "kswapd0"
    #0 [ffff8813dedfb938] __schedule at ffffffff8173f405
    #1 [ffff8813dedfb990] schedule at ffffffff8173fa27
    #2 [ffff8813dedfb9b0] schedule_timeout at ffffffff81742fec
    #3 [ffff8813dedfba60] io_schedule_timeout at ffffffff8173f186
    #4 [ffff8813dedfbaa0] bit_wait_io at ffffffff8174034f
    #5 [ffff8813dedfbac0] __wait_on_bit at ffffffff8173fec8
    #6 [ffff8813dedfbb10] out_of_line_wait_on_bit at ffffffff8173ff81
    #7 [ffff8813dedfbb90] __make_buffer_clean at ffffffffa038736f [dm_bufio]
    #8 [ffff8813dedfbbb0] __try_evict_buffer at ffffffffa0387bb8 [dm_bufio]
    #9 [ffff8813dedfbbd0] dm_bufio_shrink_scan at ffffffffa0387cc3 [dm_bufio]
    #10 [ffff8813dedfbc40] shrink_slab at ffffffff811a87ce
    #11 [ffff8813dedfbd30] shrink_zone at ffffffff811ad778
    #12 [ffff8813dedfbdc0] kswapd at ffffffff811ae92f
    #13 [ffff8813dedfbec0] kthread at ffffffff810a8428
    #14 [ffff8813dedfbf50] ret_from_fork at ffffffff81745242

    PID: 14127 TASK: ffff881455749c00 CPU: 11 COMMAND: "loop1"
    #0 [ffff88272f5af228] __schedule at ffffffff8173f405
    #1 [ffff88272f5af280] schedule at ffffffff8173fa27
    #2 [ffff88272f5af2a0] schedule_preempt_disabled at ffffffff8173fd5e
    #3 [ffff88272f5af2b0] __mutex_lock_slowpath at ffffffff81741fb5
    #4 [ffff88272f5af330] mutex_lock at ffffffff81742133
    #5 [ffff88272f5af350] dm_bufio_shrink_count at ffffffffa03865f9 [dm_bufio]
    #6 [ffff88272f5af380] shrink_slab at ffffffff811a86bd
    #7 [ffff88272f5af470] shrink_zone at ffffffff811ad778
    #8 [ffff88272f5af500] do_try_to_free_pages at ffffffff811adb34
    #9 [ffff88272f5af590] try_to_free_pages at ffffffff811adef8
    #10 [ffff88272f5af610] __alloc_pages_nodemask at ffffffff811a09c3
    #11 [ffff88272f5af710] alloc_pages_current at ffffffff811e8b71
    #12 [ffff88272f5af760] new_slab at ffffffff811f4523
    #13 [ffff88272f5af7b0] __slab_alloc at ffffffff8173a1b5
    #14 [ffff88272f5af880] kmem_cache_alloc at ffffffff811f484b
    #15 [ffff88272f5af8d0] do_blockdev_direct_IO at ffffffff812535b3
    #16 [ffff88272f5afb00] __blockdev_direct_IO at ffffffff81255dc3
    #17 [ffff88272f5afb30] xfs_vm_direct_IO at ffffffffa01fe3fc [xfs]
    #18 [ffff88272f5afb90] generic_file_read_iter at ffffffff81198994
    #19 [ffff88272f5afc50] __dta_xfs_file_read_iter_2398 at ffffffffa020c970 [xfs]
    #20 [ffff88272f5afcc0] lo_rw_aio at ffffffffa0377042 [loop]
    #21 [ffff88272f5afd70] loop_queue_work at ffffffffa0377c3b [loop]
    #22 [ffff88272f5afe60] kthread_worker_fn at ffffffff810a8a0c
    #23 [ffff88272f5afec0] kthread at ffffffff810a8428
    #24 [ffff88272f5aff50] ret_from_fork at ffffffff81745242

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Cc: stable@vger.kernel.org

    ---
    drivers/block/loop.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    Index: linux-2.6/drivers/block/loop.c
    ===================================================================
    --- linux-2.6.orig/drivers/block/loop.c 2019-08-08 17:02:50.000000000 +0200
    +++ linux-2.6/drivers/block/loop.c 2019-08-08 17:08:14.000000000 +0200
    @@ -885,7 +885,7 @@ static void loop_unprepare_queue(struct

    static int loop_kthread_worker_fn(void *worker_ptr)
    {
    - current->flags |= PF_LESS_THROTTLE;
    + current->flags |= PF_LESS_THROTTLE | PF_MEMALLOC_NOIO;
    return kthread_worker_fn(worker_ptr);
    }

    \
     
     \ /
      Last update: 2019-08-08 17:18    [W:4.462 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site