c18ff376db
In VDOA_MODE, _get_vdoa_ipu_res() would lock ipu_ch_tbl.lock mutex first, then lock vdoa_lock mutex and finally unlock ipu_ch_tbl.lock mutex. The vdoa_lock mutex is unlocked until put_vdoa_ipu_res(). Since the two mutexes are not unlocked in a reversed order as they are locked, AB-BA deadlock issue may happen as the below warning shows, which can be detected with the debug option CONFIG_PROVE_LOCKING enabled. [ 52.398770] ====================================================== [ 52.404957] WARNING: possible circular locking dependency detected [ 52.411145] 5.4.24 #1477 Not tainted [ 52.414728] ------------------------------------------------------ [ 52.420915] ipu1_task/92 is trying to acquire lock: [ 52.425800] 81f02274 (&ipu_ch_tbl.lock){+.+.}, at: get_res_do_task+0x144/0x77c [ 52.433050] [ 52.433050] but task is already holding lock: [ 52.438888] 8183189c (vdoa_lock){+.+.}, at: vdoa_get_handle+0x64/0x158 [ 52.445434] [ 52.445434] which lock already depends on the new lock. [ 52.445434] [ 52.453615] [ 52.453615] the existing dependency chain (in reverse order) is: [ 52.461101] [ 52.461101] -> #1 (vdoa_lock){+.+.}: [ 52.466175] __mutex_lock+0xb8/0xaa8 [ 52.470283] mutex_lock_nested+0x2c/0x34 [ 52.474735] vdoa_get_handle+0x64/0x158 [ 52.479100] _get_vdoa_ipu_res+0x2b4/0x338 [ 52.483726] get_res_do_task+0x34/0x77c [ 52.488092] ipu_task_thread+0x148/0xeb0 [ 52.492551] kthread+0x168/0x170 [ 52.496310] ret_from_fork+0x14/0x20 [ 52.500414] 0x0 [ 52.502779] [ 52.502779] -> #0 (&ipu_ch_tbl.lock){+.+.}: [ 52.508457] __lock_acquire+0x15d0/0x2588 [ 52.512995] lock_acquire+0xdc/0x280 [ 52.517103] __mutex_lock+0xb8/0xaa8 [ 52.521210] mutex_lock_nested+0x2c/0x34 [ 52.525662] get_res_do_task+0x144/0x77c [ 52.530113] ipu_task_thread+0x148/0xeb0 [ 52.534566] kthread+0x168/0x170 [ 52.538322] ret_from_fork+0x14/0x20 [ 52.542425] 0x0 [ 52.544790] [ 52.544790] other info that might help us debug this: [ 52.544790] [ 52.552797] Possible unsafe locking scenario: [ 52.552797] [ 52.558721] CPU0 CPU1 [ 52.563256] ---- ---- [ 52.567790] lock(vdoa_lock); [ 52.570853] lock(&ipu_ch_tbl.lock); [ 52.577040] lock(vdoa_lock); [ 52.582619] lock(&ipu_ch_tbl.lock); [ 52.586289] [ 52.586289] *** DEADLOCK *** [ 52.586289] [ 52.592215] 1 lock held by ipu1_task/92: [ 52.596142] #0: 8183189c (vdoa_lock){+.+.}, at: vdoa_get_handle+0x64/0x158 [ 52.603123] [ 52.603123] stack backtrace: [ 52.607493] CPU: 0 PID: 92 Comm: ipu1_task Not tainted 5.4.24 #1477 [ 52.613765] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) [ 52.620298] Backtrace: [ 52.622764] [<8010f094>] (dump_backtrace) from [<8010f3ac>] (show_stack+0x20/0x24) [ 52.630345] r7:818641a8 r6:00000000 r5:600f0193 r4:818641a8 [ 52.636026] [<8010f38c>] (show_stack) from [<80f534d8>] (dump_stack+0xbc/0xe8) [ 52.643261] [<80f5341c>] (dump_stack) from [<8019c8f4>] (print_circular_bug+0x1c4/0x214) [ 52.651361] r10:a8330000 r9:ffffffff r8:a8330000 r7:a8330550 r6:81d13b1c r5:81d13ac0 [ 52.659197] r4:81d13ac0 r3:46e9f8d1 [ 52.662783] [<8019c730>] (print_circular_bug) from [<8019cb48>] (check_noncircular+0x204/0x21c) [ 52.671492] r9:00000001 r8:81708f50 r7:00000000 r6:a8423a98 r5:a8330530 r4:a8330550 [ 52.679245] [<8019c944>] (check_noncircular) from [<8019f274>] (__lock_acquire+0x15d0/0x2588) [ 52.687778] r8:81708f50 r7:81d13ac0 r6:00000001 r5:81e93d7c r4:a8330530 [ 52.694491] [<8019dca4>] (__lock_acquire) from [<801a0b84>] (lock_acquire+0xdc/0x280) [ 52.702334] r10:00000000 r9:00000000 r8:00000000 r7:81f02274 r6:600f0113 r5:81708724 [ 52.710169] r4:00000000 [ 52.712717] [<801a0aa8>] (lock_acquire) from [<80f71938>] (__mutex_lock+0xb8/0xaa8) [ 52.720384] r10:81e93d7c r9:0000f6d0 r8:81f022e8 r7:00008f50 r6:00000000 r5:ffffe000 [ 52.728219] r4:81f02240 [ 52.730765] [<80f71880>] (__mutex_lock) from [<80f72354>] (mutex_lock_nested+0x2c/0x34) [ 52.738778] r10:00000000 r9:a8423ccc r8:81f022e8 r7:000002d0 r6:8188b6f8 r5:81f02234 [ 52.746613] r4:a4540400 [ 52.749162] [<80f72328>] (mutex_lock_nested) from [<80b8c830>] (get_res_do_task+0x144/0x77c) [ 52.757612] [<80b8c6ec>] (get_res_do_task) from [<80b8d6a0>] (ipu_task_thread+0x148/0xeb0) [ 52.765886] r10:a8139bd0 r9:a8423ccc r8:81f022e8 r7:a4540400 r6:81831604 r5:a454053c [ 52.773721] r4:600f0013 [ 52.776269] [<80b8d558>] (ipu_task_thread) from [<801684c8>] (kthread+0x168/0x170) [ 52.783849] r10:a8139bd0 r9:80b8d558 r8:81f022e8 r7:a8422000 r6:00000000 r5:a840cd00 [ 52.791684] r4:a83cc080 [ 52.794231] [<80168360>] (kthread) from [<801010b4>] (ret_from_fork+0x14/0x20) [ 52.801460] Exception stack(0xa8423fb0 to 0xa8423ff8) [ 52.806521] 3fa0: 00000000 00000000 00000000 00000000 [ 52.814711] 3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 52.822898] 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000 [ 52.829521] r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80168360 [ 52.837356] r4:a840cd00 This patch corrects the locking/unlocking sequence for the two mutexes to fix the deadlock issue. Reviewed-by: Sandor Yu <sandor.yu@nxp.com> Signed-off-by: Liu Ying <victor.liu@nxp.com> |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.