diff options
| author | Maurizio Lombardi <mlombard@redhat.com> | 2018-03-09 13:59:06 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2018-03-09 08:06:35 -0700 |
| commit | 2bbea6e117357d17842114c65e9a9cf2d13ae8a3 (patch) | |
| tree | c46934e1ac9defbb318199e60d772d819f8f2198 /drivers/cdrom/cdrom.c | |
| parent | da5ff37c7ede7aa4e6883f4dd5a83b6cf8b9837f (diff) | |
cdrom: do not call check_disk_change() inside cdrom_open()
when mounting an ISO filesystem sometimes (very rarely)
the system hangs because of a race condition between two tasks.
PID: 6766 TASK: ffff88007b2a6dd0 CPU: 0 COMMAND: "mount"
#0 [ffff880078447ae0] __schedule at ffffffff8168d605
#1 [ffff880078447b48] schedule_preempt_disabled at ffffffff8168ed49
#2 [ffff880078447b58] __mutex_lock_slowpath at ffffffff8168c995
#3 [ffff880078447bb8] mutex_lock at ffffffff8168bdef
#4 [ffff880078447bd0] sr_block_ioctl at ffffffffa00b6818 [sr_mod]
#5 [ffff880078447c10] blkdev_ioctl at ffffffff812fea50
#6 [ffff880078447c70] ioctl_by_bdev at ffffffff8123a8b3
#7 [ffff880078447c90] isofs_fill_super at ffffffffa04fb1e1 [isofs]
#8 [ffff880078447da8] mount_bdev at ffffffff81202570
#9 [ffff880078447e18] isofs_mount at ffffffffa04f9828 [isofs]
#10 [ffff880078447e28] mount_fs at ffffffff81202d09
#11 [ffff880078447e70] vfs_kern_mount at ffffffff8121ea8f
#12 [ffff880078447ea8] do_mount at ffffffff81220fee
#13 [ffff880078447f28] sys_mount at ffffffff812218d6
#14 [ffff880078447f80] system_call_fastpath at ffffffff81698c49
RIP: 00007fd9ea914e9a RSP: 00007ffd5d9bf648 RFLAGS: 00010246
RAX: 00000000000000a5 RBX: ffffffff81698c49 RCX: 0000000000000010
RDX: 00007fd9ec2bc210 RSI: 00007fd9ec2bc290 RDI: 00007fd9ec2bcf30
RBP: 0000000000000000 R8: 0000000000000000 R9: 0000000000000010
R10: 00000000c0ed0001 R11: 0000000000000206 R12: 00007fd9ec2bc040
R13: 00007fd9eb6b2380 R14: 00007fd9ec2bc210 R15: 00007fd9ec2bcf30
ORIG_RAX: 00000000000000a5 CS: 0033 SS: 002b
This task was trying to mount the cdrom. It allocated and configured a
super_block struct and owned the write-lock for the super_block->s_umount
rwsem. While exclusively owning the s_umount lock, it called
sr_block_ioctl and waited to acquire the global sr_mutex lock.
PID: 6785 TASK: ffff880078720fb0 CPU: 0 COMMAND: "systemd-udevd"
#0 [ffff880078417898] __schedule at ffffffff8168d605
#1 [ffff880078417900] schedule at ffffffff8168dc59
#2 [ffff880078417910] rwsem_down_read_failed at ffffffff8168f605
#3 [ffff880078417980] call_rwsem_down_read_failed at ffffffff81328838
#4 [ffff8800784179d0] down_read at ffffffff8168cde0
#5 [ffff8800784179e8] get_super at ffffffff81201cc7
#6 [ffff880078417a10] __invalidate_device at ffffffff8123a8de
#7 [ffff880078417a40] flush_disk at ffffffff8123a94b
#8 [ffff880078417a88] check_disk_change at ffffffff8123ab50
#9 [ffff880078417ab0] cdrom_open at ffffffffa00a29e1 [cdrom]
#10 [ffff880078417b68] sr_block_open at ffffffffa00b6f9b [sr_mod]
#11 [ffff880078417b98] __blkdev_get at ffffffff8123ba86
#12 [ffff880078417bf0] blkdev_get at ffffffff8123bd65
#13 [ffff880078417c78] blkdev_open at ffffffff8123bf9b
#14 [ffff880078417c90] do_dentry_open at ffffffff811fc7f7
#15 [ffff880078417cd8] vfs_open at ffffffff811fc9cf
#16 [ffff880078417d00] do_last at ffffffff8120d53d
#17 [ffff880078417db0] path_openat at ffffffff8120e6b2
#18 [ffff880078417e48] do_filp_open at ffffffff8121082b
#19 [ffff880078417f18] do_sys_open at ffffffff811fdd33
#20 [ffff880078417f70] sys_open at ffffffff811fde4e
#21 [ffff880078417f80] system_call_fastpath at ffffffff81698c49
RIP: 00007f29438b0c20 RSP: 00007ffc76624b78 RFLAGS: 00010246
RAX: 0000000000000002 RBX: ffffffff81698c49 RCX: 0000000000000000
RDX: 00007f2944a5fa70 RSI: 00000000000a0800 RDI: 00007f2944a5fa70
RBP: 00007f2944a5f540 R8: 0000000000000000 R9: 0000000000000020
R10: 00007f2943614c40 R11: 0000000000000246 R12: ffffffff811fde4e
R13: ffff880078417f78 R14: 000000000000000c R15: 00007f2944a4b010
ORIG_RAX: 0000000000000002 CS: 0033 SS: 002b
This task tried to open the cdrom device, the sr_block_open function
acquired the global sr_mutex lock. The call to check_disk_change()
then saw an event flag indicating a possible media change and tried
to flush any cached data for the device.
As part of the flush, it tried to acquire the super_block->s_umount
lock associated with the cdrom device.
This was the same super_block as created and locked by the previous task.
The first task acquires the s_umount lock and then the sr_mutex_lock;
the second task acquires the sr_mutex_lock and then the s_umount lock.
This patch fixes the issue by moving check_disk_change() out of
cdrom_open() and let the caller take care of it.
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/cdrom/cdrom.c')
| -rw-r--r-- | drivers/cdrom/cdrom.c | 3 |
1 files changed, 0 insertions, 3 deletions
diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c index e36d160c458f..8327478effd0 100644 --- a/drivers/cdrom/cdrom.c +++ b/drivers/cdrom/cdrom.c @@ -1152,9 +1152,6 @@ int cdrom_open(struct cdrom_device_info *cdi, struct block_device *bdev, cd_dbg(CD_OPEN, "entering cdrom_open\n"); - /* open is event synchronization point, check events first */ - check_disk_change(bdev); - /* if this was a O_NONBLOCK open and we should honor the flags, * do a quick open without drive/disc integrity checks. */ cdi->use_count++; |