(fixing Tony's address)
Felipe Balbi <ba...@ti.com> writes:
> Hi,
>
> I just noticed that commit 073db4a51ee4 (mtd: fix: avoid race condition
> when accessing mtd->usecount) caused a regression at least when removing
> m25p80. Wonder if you guys would know of a quick fix, other than
> reverting $commit in HEAD (yes, that makes the problem go away, but
> regresses on what $commit tried to fix, of course).
>
> More info about the regression follows, together with bisection log:
>
> # modprobe -r m25p80
> [ 53.419251]
> [ 53.420838] ======================================================
> [ 53.427300] [ INFO: possible circular locking dependency detected ]
> [ 53.433865] 4.3.0-rc6 #96 Not tainted
> [ 53.437686] -------------------------------------------------------
> [ 53.444220] modprobe/372 is trying to acquire lock:
> [ 53.449320] (&new->lock){+.+...}, at: [<c043fe4c>]
> del_mtd_blktrans_dev+0x80/0xdc
> [ 53.457271]
> [ 53.457271] but task is already holding lock:
> [ 53.463372] (mtd_table_mutex){+.+.+.}, at: [<c0439994>]
> del_mtd_device+0x18/0x100
> [ 53.471321]
> [ 53.471321] which lock already depends on the new lock.
> [ 53.471321]
> [ 53.479856]
> [ 53.479856] the existing dependency chain (in reverse order) is:
> [ 53.487660]
> -> #1 (mtd_table_mutex){+.+.+.}:
> [ 53.492331] [<c043fc5c>] blktrans_open+0x34/0x1a4
> [ 53.497879] [<c01afce0>] __blkdev_get+0xc4/0x3b0
> [ 53.503364] [<c01b0bb8>] blkdev_get+0x108/0x320
> [ 53.508743] [<c01713c0>] do_dentry_open+0x218/0x314
> [ 53.514496] [<c0180454>] path_openat+0x4c0/0xf9c
> [ 53.519959] [<c0182044>] do_filp_open+0x5c/0xc0
> [ 53.525336] [<c0172758>] do_sys_open+0xfc/0x1cc
> [ 53.530716] [<c000f740>] ret_fast_syscall+0x0/0x1c
> [ 53.536375]
> -> #0 (&new->lock){+.+...}:
> [ 53.540587] [<c063f124>] mutex_lock_nested+0x38/0x3cc
> [ 53.546504] [<c043fe4c>] del_mtd_blktrans_dev+0x80/0xdc
> [ 53.552606] [<c043f164>] blktrans_notify_remove+0x7c/0x84
> [ 53.558891] [<c04399f0>] del_mtd_device+0x74/0x100
> [ 53.564544] [<c043c670>] del_mtd_partitions+0x80/0xc8
> [ 53.570451] [<c0439aa0>] mtd_device_unregister+0x24/0x48
> [ 53.576637] [<c046ce6c>] spi_drv_remove+0x1c/0x34
> [ 53.582207] [<c03de0f0>] __device_release_driver+0x88/0x114
> [ 53.588663] [<c03de19c>] device_release_driver+0x20/0x2c
> [ 53.594843] [<c03dd9e8>] bus_remove_device+0xd8/0x108
> [ 53.600748] [<c03dacc0>] device_del+0x10c/0x210
> [ 53.606127] [<c03dadd0>] device_unregister+0xc/0x20
> [ 53.611849] [<c046d878>] __unregister+0x10/0x20
> [ 53.617211] [<c03da868>] device_for_each_child+0x50/0x7c
> [ 53.623387] [<c046eae8>] spi_unregister_master+0x58/0x8c
> [ 53.629578] [<c03e12f0>] release_nodes+0x15c/0x1c8
> [ 53.635223] [<c03de0f8>] __device_release_driver+0x90/0x114
> [ 53.641689] [<c03de900>] driver_detach+0xb4/0xb8
> [ 53.647147] [<c03ddc78>] bus_remove_driver+0x4c/0xa0
> [ 53.652970] [<c00cab50>] SyS_delete_module+0x11c/0x1e4
> [ 53.658976] [<c000f740>] ret_fast_syscall+0x0/0x1c
> [ 53.664621]
> [ 53.664621] other info that might help us debug this:
> [ 53.664621]
> [ 53.672979] Possible unsafe locking scenario:
> [ 53.672979]
> [ 53.679169] CPU0 CPU1
> [ 53.683900] ---- ----
> [ 53.688633] lock(mtd_table_mutex);
> [ 53.692383] lock(&new->lock);
> [ 53.698306] lock(mtd_table_mutex);
> [ 53.704658] lock(&new->lock);
> [ 53.707946]
> [ 53.707946] *** DEADLOCK ***
> [ 53.707946]
> [ 53.714123] 5 locks held by modprobe/372:
> [ 53.718305] #0: (&dev->mutex){......}, at: [<c03de890>]
> driver_detach+0x44/0xb8
> [ 53.726147] #1: (&dev->mutex){......}, at: [<c03de89c>]
> driver_detach+0x50/0xb8
> [ 53.733985] #2: (&dev->mutex){......}, at: [<c03de194>]
> device_release_driver+0x18/0x2c
> [ 53.742541] #3: (mtd_partitions_mutex){+.+.+.}, at: [<c043c60c>]
> del_mtd_partitions+0x1c/0xc8
> [ 53.751656] #4: (mtd_table_mutex){+.+.+.}, at: [<c0439994>]
> del_mtd_device+0x18/0x100
> [ 53.760048]
> [ 53.760048] stack backtrace:
> [ 53.764591] CPU: 0 PID: 372 Comm: modprobe Not tainted 4.3.0-rc6 #96
> [ 53.771217] Hardware name: Generic AM43 (Flattened Device Tree)
> [ 53.777419] [<c0017bcc>] (unwind_backtrace) from [<c0013f30>]
> (show_stack+0x10/0x14)
> [ 53.785511] [<c0013f30>] (show_stack) from [<c0346be4>]
> (dump_stack+0x84/0x9c)
> [ 53.793063] [<c0346be4>] (dump_stack) from [<c0090000>]
> (print_circular_bug+0x1c8/0x30c)
> [ 53.801500] [<c0090000>] (print_circular_bug) from [<c0093828>]
> (__lock_acquire+0x1a48/0x1cd8)
> [ 53.810480] [<c0093828>] (__lock_acquire) from [<c00943bc>]
> (lock_acquire+0xac/0x12c)
> [ 53.818649] [<c00943bc>] (lock_acquire) from [<c063f124>]
> (mutex_lock_nested+0x38/0x3cc)
> [ 53.827103] [<c063f124>] (mutex_lock_nested) from [<c043fe4c>]
> (del_mtd_blktrans_dev+0x80/0xdc)
> [ 53.836199] [<c043fe4c>] (del_mtd_blktrans_dev) from [<c043f164>]
> (blktrans_notify_remove+0x7c/0x84)
> [ 53.845735] [<c043f164>] (blktrans_notify_remove) from [<c04399f0>]
> (del_mtd_device+0x74/0x100)
> [ 53.854833] [<c04399f0>] (del_mtd_device) from [<c043c670>]
> (del_mtd_partitions+0x80/0xc8)
> [ 53.863469] [<c043c670>] (del_mtd_partitions) from [<c0439aa0>]
> (mtd_device_unregister+0x24/0x48)
> [ 53.872733] [<c0439aa0>] (mtd_device_unregister) from [<c046ce6c>]
> (spi_drv_remove+0x1c/0x34)
> [ 53.881633] [<c046ce6c>] (spi_drv_remove) from [<c03de0f0>]
> (__device_release_driver+0x88/0x114)
> [ 53.890788] [<c03de0f0>] (__device_release_driver) from [<c03de19c>]
> (device_release_driver+0x20/0x2c)
> [ 53.900483] [<c03de19c>] (device_release_driver) from [<c03dd9e8>]
> (bus_remove_device+0xd8/0x108)
> [ 53.909735] [<c03dd9e8>] (bus_remove_device) from [<c03dacc0>]
> (device_del+0x10c/0x210)
> [ 53.918088] [<c03dacc0>] (device_del) from [<c03dadd0>]
> (device_unregister+0xc/0x20)
> [ 53.926160] [<c03dadd0>] (device_unregister) from [<c046d878>]
> (__unregister+0x10/0x20)
> [ 53.934526] [<c046d878>] (__unregister) from [<c03da868>]
> (device_for_each_child+0x50/0x7c)
> [ 53.943261] [<c03da868>] (device_for_each_child) from [<c046eae8>]
> (spi_unregister_master+0x58/0x8c)
> [ 53.952805] [<c046eae8>] (spi_unregister_master) from [<c03e12f0>]
> (release_nodes+0x15c/0x1c8)
> [ 53.961809] [<c03e12f0>] (release_nodes) from [<c03de0f8>]
> (__device_release_driver+0x90/0x114)
> [ 53.970883] [<c03de0f8>] (__device_release_driver) from [<c03de900>]
> (driver_detach+0xb4/0xb8)
> [ 53.979864] [<c03de900>] (driver_detach) from [<c03ddc78>]
> (bus_remove_driver+0x4c/0xa0)
> [ 53.988303] [<c03ddc78>] (bus_remove_driver) from [<c00cab50>]
> (SyS_delete_module+0x11c/0x1e4)
> [ 53.997285] [<c00cab50>] (SyS_delete_module) from [<c000f740>]
> (ret_fast_syscall+0x0/0x1c)
>
>
> Bisection log:
>
> git bisect start
> # good: [b953c0d234bc72e8489d3bf51a276c5c4ec85345] Linux 4.1
> git bisect good b953c0d234bc72e8489d3bf51a276c5c4ec85345
> # bad: [d770e558e21961ad6cfdf0ff7df0eb5d7d4f0754] Linux 4.2-rc1
> git bisect bad d770e558e21961ad6cfdf0ff7df0eb5d7d4f0754
> # bad: [4570a37169d4b44d316f40b2ccc681dc93fedc7b] Merge tag 'sound-4.2-rc1'
> of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
> git bisect bad 4570a37169d4b44d316f40b2ccc681dc93fedc7b
> # bad: [4e241557fc1cb560bd9e77ca1b4a9352732a5427] Merge tag 'for-linus' of
> git://git.kernel.org/pub/scm/virt/kvm/kvm
> git bisect bad 4e241557fc1cb560bd9e77ca1b4a9352732a5427
> # good: [44d21c3f3a2ef2f58b18bda64c52c99e723f3f4a] Merge
> git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
> git bisect good 44d21c3f3a2ef2f58b18bda64c52c99e723f3f4a
> # good: [acd53127c4adbd34570b221e7ea1f7fc94aea923] Merge tag 'scsi-misc' of
> git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
> git bisect good acd53127c4adbd34570b221e7ea1f7fc94aea923
> # bad: [54245ed870c8cf9ff87fdf78955ffbc93b261e9f] Merge tag
> 'for-linus-20150623' of git://git.infradead.org/linux-mtd
> git bisect bad 54245ed870c8cf9ff87fdf78955ffbc93b261e9f
> # good: [5a602e157a9d91d5ce98d07c404097edba8ec9f3] Merge tag 'spi-v4.2' of
> git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi
> git bisect good 5a602e157a9d91d5ce98d07c404097edba8ec9f3
> # good: [1abf25a25b86dcfe28d243a5af71bd1c9d6de1ef] mfd: lpc_ich: Assign
> subdevice ids automatically
> git bisect good 1abf25a25b86dcfe28d243a5af71bd1c9d6de1ef
> # bad: [45c2ebd702a468d5037cf16aa4f8ea8d67776f6a] mtd: docg3: Don't leak
> docg3->bbt in error path
> git bisect bad 45c2ebd702a468d5037cf16aa4f8ea8d67776f6a
> # bad: [f628ece6636c2f0354a52566cafdea6d2f963b3d] mtd: brcmnand: add BCM63138
> support
> git bisect bad f628ece6636c2f0354a52566cafdea6d2f963b3d
> # good: [b94665322b786a806a0169752ff2f35f3f467b99] mtd: samsung: Constify
> platform_device_id
> git bisect good b94665322b786a806a0169752ff2f35f3f467b99
> # bad: [073db4a51ee43ccb827f54a4261c0583b028d5ab] mtd: fix: avoid race
> condition when accessing mtd->usecount
> git bisect bad 073db4a51ee43ccb827f54a4261c0583b028d5ab
> # good: [b79c332fb283c101abb5d8570dea2d29f3871802] mtd: spi-nor: add support
> for the ISSI SI25CD512 SPI flash
> git bisect good b79c332fb283c101abb5d8570dea2d29f3871802
> # good: [7aaea7605c0e19fa7b38d7ac5dcd818942fd17a7] jffs2: fix unbalanced
> locking
> git bisect good 7aaea7605c0e19fa7b38d7ac5dcd818942fd17a7
> # good: [5844feeaa4154d1c46d3462c7a4653d22356d8b4] mtd: nand: add common DT
> init code
> git bisect good 5844feeaa4154d1c46d3462c7a4653d22356d8b4
> # first bad commit: [073db4a51ee43ccb827f54a4261c0583b028d5ab] mtd: fix:
> avoid race condition when accessing mtd->usecount
> commit 073db4a51ee43ccb827f54a4261c0583b028d5ab
> Author: Brian Norris <computersforpe...@gmail.com>
> Date: Thu May 7 17:55:16 2015 -0700
>
> mtd: fix: avoid race condition when accessing mtd->usecount
>
> On A MIPS 32-cores machine a BUG_ON was triggered because some acesses to
> mtd->usecount were done without taking mtd_table_mutex.
> kernel: Call Trace:
> kernel: [<ffffffff80401818>] __put_mtd_device+0x20/0x50
> kernel: [<ffffffff804086f4>] blktrans_release+0x8c/0xd8
> kernel: [<ffffffff802577e0>] __blkdev_put+0x1a8/0x200
> kernel: [<ffffffff802579a4>] blkdev_close+0x1c/0x30
> kernel: [<ffffffff8022006c>] __fput+0xac/0x250
> kernel: [<ffffffff80171208>] task_work_run+0xd8/0x120
> kernel: [<ffffffff8012c23c>] work_notifysig+0x10/0x18
> kernel:
> kernel:
> Code: 2442ffff ac8202d8 000217fe <00020336> dc820128 10400003
> 00000000 0040f809 00000000
> kernel: ---[ end trace 080fbb4579b47a73 ]---
>
> Fixed by taking the mutex in blktrans_open and blktrans_release.
>
> Note that this locking is already suggested in
> include/linux/mtd/blktrans.h:
>
> struct mtd_blktrans_ops {
> ...
> /* Called with mtd_table_mutex held; no race with add/remove */
> int (*open)(struct mtd_blktrans_dev *dev);
> void (*release)(struct mtd_blktrans_dev *dev);
> ...
> };
>
> But we weren't following it.
>
> Originally reported by (and patched by) Zhang and Giuseppe,
> independently. Improved and rewritten.
>
> Cc: sta...@vger.kernel.org
> Reported-by: Zhang Xingcai <zhangxing...@huawei.com>
> Reported-by: Giuseppe Cantavenera <giuseppe.cantavenera....@nokia.com>
> Tested-by: Giuseppe Cantavenera <giuseppe.cantavenera....@nokia.com>
> Acked-by: Alexander Sverdlin <alexander.sverd...@nokia.com>
> Signed-off-by: Brian Norris <computersforpe...@gmail.com>
>
> diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
> index 2b0c52870999..df7c6c70757a 100644
> --- a/drivers/mtd/mtd_blkdevs.c
> +++ b/drivers/mtd/mtd_blkdevs.c
> @@ -197,6 +197,7 @@ static int blktrans_open(struct block_device *bdev,
> fmode_t mode)
> return -ERESTARTSYS; /* FIXME: busy loop! -arnd*/
>
> mutex_lock(&dev->lock);
> + mutex_lock(&mtd_table_mutex);
>
> if (dev->open)
> goto unlock;
> @@ -220,6 +221,7 @@ static int blktrans_open(struct block_device *bdev,
> fmode_t mode)
>
> unlock:
> dev->open++;
> + mutex_unlock(&mtd_table_mutex);
> mutex_unlock(&dev->lock);
> blktrans_dev_put(dev);
> return ret;
> @@ -230,6 +232,7 @@ error_release:
> error_put:
> module_put(dev->tr->owner);
> kref_put(&dev->ref, blktrans_dev_release);
> + mutex_unlock(&mtd_table_mutex);
> mutex_unlock(&dev->lock);
> blktrans_dev_put(dev);
> return ret;
> @@ -243,6 +246,7 @@ static void blktrans_release(struct gendisk *disk,
> fmode_t mode)
> return;
>
> mutex_lock(&dev->lock);
> + mutex_lock(&mtd_table_mutex);
>
> if (--dev->open)
> goto unlock;
> @@ -256,6 +260,7 @@ static void blktrans_release(struct gendisk *disk,
> fmode_t mode)
> __put_mtd_device(dev->mtd);
> }
> unlock:
> + mutex_unlock(&mtd_table_mutex);
> mutex_unlock(&dev->lock);
> blktrans_dev_put(dev);
> }
>
> --
> balbi-- balbi
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