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| author | Petr Uzel <petr.uzel@suse.cz> | 2011-03-03 11:48:50 -0500 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2011-03-03 11:53:25 -0500 |
| commit | fd51469fb68b987032e46297e0a4fe9020063c20 (patch) | |
| tree | a108634afe0a0b2113f5df6ef5c00be2087f51c3 /drivers | |
| parent | 2d3a8497f8cc5aca14b722cd37d51f6c15ff9f74 (diff) | |
| download | lwn-fd51469fb68b987032e46297e0a4fe9020063c20.tar.gz lwn-fd51469fb68b987032e46297e0a4fe9020063c20.zip | |
block: kill loop_mutex
Following steps lead to deadlock in kernel:
dd if=/dev/zero of=img bs=512 count=1000
losetup -f img
mkfs.ext2 /dev/loop0
mount -t ext2 -o loop /dev/loop0 mnt
umount mnt/
Stacktrace:
[<c102ec04>] irq_exit+0x36/0x59
[<c101502c>] smp_apic_timer_interrupt+0x6b/0x75
[<c127f639>] apic_timer_interrupt+0x31/0x38
[<c101df88>] mutex_spin_on_owner+0x54/0x5b
[<fe2250e9>] lo_release+0x12/0x67 [loop]
[<c10c4eae>] __blkdev_put+0x7c/0x10c
[<c10a4da5>] fput+0xd5/0x1aa
[<fe2250cf>] loop_clr_fd+0x1a9/0x1b1 [loop]
[<fe225110>] lo_release+0x39/0x67 [loop]
[<c10c4eae>] __blkdev_put+0x7c/0x10c
[<c10a59d9>] deactivate_locked_super+0x17/0x36
[<c10b6f37>] sys_umount+0x27e/0x2a5
[<c10b6f69>] sys_oldumount+0xb/0xe
[<c1002897>] sysenter_do_call+0x12/0x26
[<ffffffff>] 0xffffffff
Regression since 2a48fc0ab24241755dc9, which introduced the private
loop_mutex as part of the BKL removal process.
As per [1], the mutex can be safely removed.
[1] http://www.gossamer-threads.com/lists/linux/kernel/1341930
Addresses: https://bugzilla.novell.com/show_bug.cgi?id=669394
Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=29172
Signed-off-by: Petr Uzel <petr.uzel@suse.cz>
Cc: stable@kernel.org
Reviewed-by: Nikanth Karthikesan <knikanth@suse.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/block/loop.c | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 49e6a545eb63..dbf31ec9114d 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -78,7 +78,6 @@ #include <asm/uaccess.h> -static DEFINE_MUTEX(loop_mutex); static LIST_HEAD(loop_devices); static DEFINE_MUTEX(loop_devices_mutex); @@ -1501,11 +1500,9 @@ static int lo_open(struct block_device *bdev, fmode_t mode) { struct loop_device *lo = bdev->bd_disk->private_data; - mutex_lock(&loop_mutex); mutex_lock(&lo->lo_ctl_mutex); lo->lo_refcnt++; mutex_unlock(&lo->lo_ctl_mutex); - mutex_unlock(&loop_mutex); return 0; } @@ -1515,7 +1512,6 @@ static int lo_release(struct gendisk *disk, fmode_t mode) struct loop_device *lo = disk->private_data; int err; - mutex_lock(&loop_mutex); mutex_lock(&lo->lo_ctl_mutex); if (--lo->lo_refcnt) @@ -1540,7 +1536,6 @@ static int lo_release(struct gendisk *disk, fmode_t mode) out: mutex_unlock(&lo->lo_ctl_mutex); out_unlocked: - mutex_unlock(&loop_mutex); return 0; } |