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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> |
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| aec62xx.c | ||
| ali14xx.c | ||
| alim15x3.c | ||
| amd74xx.c | ||
| atiixp.c | ||
| au1xxx-ide.c | ||
| buddha.c | ||
| cmd64x.c | ||
| cmd640.c | ||
| cs5520.c | ||
| cs5530.c | ||
| cs5535.c | ||
| cs5536.c | ||
| cy82c693.c | ||
| delkin_cb.c | ||
| dtc2278.c | ||
| falconide.c | ||
| gayle.c | ||
| hpt366.c | ||
| ht6560b.c | ||
| icside.c | ||
| ide-4drives.c | ||
| ide-acpi.c | ||
| ide-atapi.c | ||
| ide-cd.c | ||
| ide-cd.h | ||
| ide-cd_ioctl.c | ||
| ide-cd_verbose.c | ||
| ide-cs.c | ||
| ide-devsets.c | ||
| ide-disk.c | ||
| ide-disk.h | ||
| ide-disk_ioctl.c | ||
| ide-disk_proc.c | ||
| ide-dma-sff.c | ||
| ide-dma.c | ||
| ide-eh.c | ||
| ide-floppy.c | ||
| ide-floppy.h | ||
| ide-floppy_ioctl.c | ||
| ide-floppy_proc.c | ||
| ide-gd.c | ||
| ide-gd.h | ||
| ide-generic.c | ||
| ide-io-std.c | ||
| ide-io.c | ||
| ide-ioctls.c | ||
| ide-iops.c | ||
| ide-legacy.c | ||
| ide-lib.c | ||
| ide-park.c | ||
| ide-pci-generic.c | ||
| ide-pio-blacklist.c | ||
| ide-pm.c | ||
| ide-pnp.c | ||
| ide-probe.c | ||
| ide-proc.c | ||
| ide-scan-pci.c | ||
| ide-sysfs.c | ||
| ide-tape.c | ||
| ide-taskfile.c | ||
| ide-timings.c | ||
| ide-xfer-mode.c | ||
| ide.c | ||
| ide_platform.c | ||
| it821x.c | ||
| it8172.c | ||
| it8213.c | ||
| jmicron.c | ||
| Kconfig | ||
| macide.c | ||
| Makefile | ||
| ns87415.c | ||
| opti621.c | ||
| palm_bk3710.c | ||
| pdc202xx_new.c | ||
| pdc202xx_old.c | ||
| piix.c | ||
| pmac.c | ||
| q40ide.c | ||
| qd65xx.c | ||
| qd65xx.h | ||
| rapide.c | ||
| rz1000.c | ||
| sc1200.c | ||
| serverworks.c | ||
| setup-pci.c | ||
| sgiioc4.c | ||
| siimage.c | ||
| sis5513.c | ||
| sl82c105.c | ||
| slc90e66.c | ||
| tc86c001.c | ||
| triflex.c | ||
| trm290.c | ||
| tx4938ide.c | ||
| tx4939ide.c | ||
| umc8672.c | ||
| via82cxxx.c | ||