Subject: Re: [PATCH] platform/x86: ISST: do not hold lock punit_misc_dev_lock
 when register misc
To:     Hans de Goede <hdegoede@redhat.com>,
        SrinivasPandruvada <srinivas.pandruvada@linux.intel.com>,
        MarkGross <markgross@kernel.org>
Cc:     platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20220111103122.32362-1-liwei.song@windriver.com>
 <9e5fd9f2-dda7-73ef-00a8-203da3827e9d@redhat.com>
From:   Liwei Song <liwei.song@windriver.com>
Message-ID: <8809e11c-191e-036a-9066-90cc316f83b9@windriver.com>
Date:   Tue, 11 Jan 2022 19:57:20 +0800
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On 1/11/22 18:39, Hans de Goede wrote:
> Hi,
> 
> On 1/11/22 11:31, Liwei Song wrote:
>> exist the below call sequences may cause deadlock:
>>
>> isst_if_probe()
>>    --> isst_if_cdev_register()
>>       --> mutex_lock(&punit_misc_dev_lock)
>>    --> misc_register()
>>       --> mutex_lock(&misc_mtx)
>>
>> misc_open()
>>    --> mutex_lock(&misc_mtx)
>>    --> isst_if_open()
>>       --> mutex_lock(&punit_misc_dev_lock)
>>
>> to fix this do not hold punit_misc_dev_lock when call misc_register
>> since it has misc_mtx lock for sync.
> 
> I agree that the punit_misc_dev_lock should not be hold during
> (un)registration, but this fix looks wrong with unlocking + relocking it.
> 
> Normally things like this are done by setting up everything which needs
> to be setup before calling misc_register() and in that case the
> setup code does not need to lock the punit_misc_dev_lock at all since
> none of the misc_dev callbacks can be called before everything is
> setup (and the same in reverse for unregister, unregister the misc-dev
> before doing any teardown, then there is no need for the lock).
> 
> Note the above assumes that the punit_misc_dev_lock is only used
> from misc-dev callbacks based on its name, I did not check this is true.

Hi Hans,

Thanks for your input, in my case there are two devices on my board
will trigger the probe routine(isst_if_probe and isst_if_mbox_probe),
both of them will call misc_register(), punit_misc_dev_lock is also
used by the probe.

Thanks,
Liwei.


> 
> Srinivas, can you take a look please ? And see if you can come up
> with a better fix ?
> 
> Regards,
> 
> Hans
> 
> 
> 
> 
>>
>> [  256.104522] ======================================================
>> [  256.113783] WARNING: possible circular locking dependency detected
>> [  256.120093] 5.16.0-rc6-yocto-standard+ #99 Not tainted
>> [  256.125362] ------------------------------------------------------
>> [  256.131673] intel-speed-sel/844 is trying to acquire lock:
>> [  256.137290] ffffffffc036f0d0 (punit_misc_dev_lock){+.+.}-{3:3}, at: isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.147171]
>> [  256.147171] but task is already holding lock:
>> [  256.153135] ffffffff8ee7cb50 (misc_mtx){+.+.}-{3:3}, at: misc_open+0x2a/0x170
>> [  256.160407]
>> [  256.160407] which lock already depends on the new lock.
>> [  256.160407]
>> [  256.168712]
>> [  256.168712] the existing dependency chain (in reverse order) is:
>> [  256.176327]
>> [  256.176327] -> #1 (misc_mtx){+.+.}-{3:3}:
>> [  256.181946]        lock_acquire+0x1e6/0x330
>> [  256.186265]        __mutex_lock+0x9b/0x9b0
>> [  256.190497]        mutex_lock_nested+0x1b/0x20
>> [  256.195075]        misc_register+0x32/0x1a0
>> [  256.199390]        isst_if_cdev_register+0x65/0x180 [isst_if_common]
>> [  256.205878]        isst_if_probe+0x144/0x16e [isst_if_mmio]
>> [  256.209991] hrtimer: interrupt took 10370 ns
>> [  256.211582]        local_pci_probe+0x47/0xa0
>> [  256.220384]        work_for_cpu_fn+0x17/0x30
>> [  256.224790]        process_one_work+0x26a/0x650
>> [  256.229456]        worker_thread+0x1dd/0x3b0
>> [  256.233861]        kthread+0x191/0x1c0
>> [  256.237745]        ret_from_fork+0x1f/0x30
>> [  256.241976]
>> [  256.241976] -> #0 (punit_misc_dev_lock){+.+.}-{3:3}:
>> [  256.248552]        validate_chain+0xbc6/0x1750
>> [  256.253131]        __lock_acquire+0x88c/0xc10
>> [  256.257618]        lock_acquire+0x1e6/0x330
>> [  256.261933]        __mutex_lock+0x9b/0x9b0
>> [  256.266165]        mutex_lock_nested+0x1b/0x20
>> [  256.270739]        isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.276356]        misc_open+0x100/0x170
>> [  256.280409]        chrdev_open+0xa5/0x1e0
>> [  256.284550]        do_dentry_open+0x23d/0x3c0
>> [  256.289039]        vfs_open+0x2f/0x40
>> [  256.292836]        path_openat+0x87a/0x940
>> [  256.297064]        do_filp_open+0xc5/0x140
>> [  256.301295]        do_sys_openat2+0x23d/0x320
>> [  256.305782]        do_sys_open+0x59/0x80
>> [  256.309836]        __x64_sys_openat+0x20/0x30
>> [  256.314324]        do_syscall_64+0x3f/0x90
>> [  256.318552]        entry_SYSCALL_64_after_hwframe+0x44/0xae
>> [  256.324259]
>> [  256.324259] other info that might help us debug this:
>> [  256.324259]
>> [  256.332394]  Possible unsafe locking scenario:
>> [  256.332394]
>> [  256.338444]        CPU0                    CPU1
>> [  256.343105]        ----                    ----
>> [  256.347768]   lock(misc_mtx);
>> [  256.350870]                                lock(punit_misc_dev_lock);
>> [  256.357441]                                lock(misc_mtx);
>> [  256.363058]   lock(punit_misc_dev_lock);
>> [  256.367110]
>> [  256.367110]  *** DEADLOCK ***
>> [  256.367110]
>> [  256.373162] 1 lock held by intel-speed-sel/844:
>> [  256.377824]  #0: ffffffff8ee7cb50 (misc_mtx){+.+.}-{3:3}, at: misc_open+0x2a/0x170
>> [  256.385531]
>> [  256.385531] stack backtrace:
>> [  256.390021] CPU: 12 PID: 844 Comm: intel-speed-sel Not tainted 5.16.0-rc6-yocto-standard+ #99
>> [  256.398678] Hardware name: ACCTON MOROCITY/MOROCITY, BIOS IDVLCRB1.86B.0021.D09.2111010103 11/01/2021
>> [  256.408028] Call Trace:
>> [  256.410605]  <TASK>
>> [  256.412837]  dump_stack_lvl+0x5b/0x82
>> [  256.416635]  dump_stack+0x10/0x12
>> [  256.420085]  print_circular_bug.isra.43+0x261/0x2c0
>> [  256.425095]  check_noncircular+0x126/0x140
>> [  256.429326]  ? __this_cpu_preempt_check+0x13/0x20
>> [  256.434167]  validate_chain+0xbc6/0x1750
>> [  256.438223]  ? validate_chain+0xbc6/0x1750
>> [  256.442451]  ? validate_chain+0x236/0x1750
>> [  256.446687]  __lock_acquire+0x88c/0xc10
>> [  256.450658]  lock_acquire+0x1e6/0x330
>> [  256.454452]  ? isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.459726]  ? __mutex_lock+0x79/0x9b0
>> [  256.463610]  ? __mutex_lock+0x79/0x9b0
>> [  256.467493]  ? isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.472764]  ? isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.478038]  __mutex_lock+0x9b/0x9b0
>> [  256.481748]  ? isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.487021]  ? __mutex_lock+0x102/0x9b0
>> [  256.490993]  ? __this_cpu_preempt_check+0x13/0x20
>> [  256.495837]  mutex_lock_nested+0x1b/0x20
>> [  256.499893]  ? mutex_lock_nested+0x1b/0x20
>> [  256.504121]  isst_if_open+0x18/0x90 [isst_if_common]
>> [  256.509222]  misc_open+0x100/0x170
>> [  256.512759]  chrdev_open+0xa5/0x1e0
>> [  256.516386]  ? cdev_put.part.1+0x20/0x20
>> [  256.520441]  do_dentry_open+0x23d/0x3c0
>> [  256.524414]  vfs_open+0x2f/0x40
>> [  256.527689]  path_openat+0x87a/0x940
>> [  256.531399]  do_filp_open+0xc5/0x140
>> [  256.535112]  ? trace_preempt_on+0x28/0xd0
>> [  256.539255]  ? alloc_fd+0x152/0x230
>> [  256.542880]  ? preempt_count_sub+0x9b/0x100
>> [  256.547200]  ? _raw_spin_unlock+0x2c/0x50
>> [  256.551348]  do_sys_openat2+0x23d/0x320
>> [  256.555320]  ? do_sys_openat2+0x23d/0x320
>> [  256.559467]  do_sys_open+0x59/0x80
>> [  256.563003]  __x64_sys_openat+0x20/0x30
>> [  256.566972]  do_syscall_64+0x3f/0x90
>> [  256.570680]  entry_SYSCALL_64_after_hwframe+0x44/0xae
>> [  256.575866] RIP: 0033:0x7f9be4b97c27
>> [  256.579576] Code: 25 00 00 41 00 3d 00 00 41 00 74 37 64 8b 04 25 18 00 00 00 85 c0 75 5b 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 85 00 00 00 48 83 c4 68 5d 41 5c c3 0f 1f
>> [  256.598474] RSP: 002b:00007ffd8fc01b70 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
>> [  256.606177] RAX: ffffffffffffffda RBX: 00005572f20332b0 RCX: 00007f9be4b97c27
>> [  256.613443] RDX: 0000000000000000 RSI: 00005572f202936a RDI: 00000000ffffff9c
>> [  256.620709] RBP: 00005572f202936a R08: 0000000000000008 R09: 0000000000000001
>> [  256.627974] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
>> [  256.635241] R13: 00005572f20332b0 R14: 0000000000000001 R15: 0000000000000000
>> [  256.642513]  </TASK>
>>
>> Signed-off-by: Liwei Song <liwei.song@windriver.com>
>> ---
>>  drivers/platform/x86/intel/speed_select_if/isst_if_common.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
>> index c9a85eb2e860..bcbc0d508ec4 100644
>> --- a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
>> +++ b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
>> @@ -693,10 +693,12 @@ int isst_if_cdev_register(int device_type, struct isst_if_cmd_cb *cb)
>>  	if (!misc_usage_count) {
>>  		int ret;
>>  
>> +		mutex_unlock(&punit_misc_dev_lock);
>>  		misc_device_ret = misc_register(&isst_if_char_driver);
>>  		if (misc_device_ret)
>> -			goto unlock_exit;
>> +			return misc_device_ret;
>>  
>> +		mutex_lock(&punit_misc_dev_lock);
>>  		ret = isst_if_cpu_info_init();
>>  		if (ret) {
>>  			misc_deregister(&isst_if_char_driver);
>> @@ -731,7 +733,9 @@ void isst_if_cdev_unregister(int device_type)
>>  	if (device_type == ISST_IF_DEV_MBOX)
>>  		isst_delete_hash();
>>  	if (!misc_usage_count && !misc_device_ret) {
>> +		mutex_unlock(&punit_misc_dev_lock);
>>  		misc_deregister(&isst_if_char_driver);
>> +		mutex_lock(&punit_misc_dev_lock);
>>  		isst_if_cpu_info_exit();
>>  	}
>>  	mutex_unlock(&punit_misc_dev_lock);
>>
>