linux-kernel - Re: [PATCH v2] i3c: Use i3cdev->desc->info instead of calling i3c_device_get

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Message-ID: <89b5778b-d251-4777-bb6c-54f56740d277@ijzerbout.nl>
Date: Tue, 19 Nov 2024 22:19:33 +0100
From: Kees Bakker <kees@...erbout.nl>
To: mtk25126 <defa.li@...iatek.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 wsd_upstream@...iatek.com, mingchang.jia@...iatek.com,
 yuhan.wei@...iatek.com, hao.lin@...iatek.com
Subject: Re: [PATCH v2] i3c: Use i3cdev->desc->info instead of calling
 i3c_device_get_info() to avoid deadlock

Op 19-11-2024 om 21:51 schreef Kees Bakker:
> Op 07-11-2024 om 14:25 schreef mtk25126:
>> From: Defa Li <defa.li@...iatek.com>
>>
>> A deadlock may happen since the i3c_master_register() acquires
>> &i3cbus->lock twice. See the log below.
>> Use i3cdev->desc->info instead of calling i3c_device_info() to
>> avoid acquiring the lock twice.
>>
>> v2:
>>    - Modified the title and commit message
>>
>> ============================================
>> WARNING: possible recursive locking detected
>> 6.11.0-mainline
>> --------------------------------------------
>> init/1 is trying to acquire lock:
>> f1ffff80a6a40dc0 (&i3cbus->lock){++++}-{3:3}, at: i3c_bus_normaluse_lock
>>
>> but task is already holding lock:
>> f1ffff80a6a40dc0 (&i3cbus->lock){++++}-{3:3}, at: i3c_master_register
>>
>> other info that might help us debug this:
>>   Possible unsafe locking scenario:
>>
>>         CPU0
>>         ----
>>    lock(&i3cbus->lock);
>>    lock(&i3cbus->lock);
>>
>>   *** DEADLOCK ***
>>
>>   May be due to missing lock nesting notation
>>
>> 2 locks held by init/1:
>>   #0: fcffff809b6798f8 (&dev->mutex){....}-{3:3}, at: __driver_attach
>>   #1: f1ffff80a6a40dc0 (&i3cbus->lock){++++}-{3:3}, at: 
>> i3c_master_register
>>
>> stack backtrace:
>> CPU: 6 UID: 0 PID: 1 Comm: init
>> Call trace:
>>   dump_backtrace+0xfc/0x17c
>>   show_stack+0x18/0x28
>>   dump_stack_lvl+0x40/0xc0
>>   dump_stack+0x18/0x24
>>   print_deadlock_bug+0x388/0x390
>>   __lock_acquire+0x18bc/0x32ec
>>   lock_acquire+0x134/0x2b0
>>   down_read+0x50/0x19c
>>   i3c_bus_normaluse_lock+0x14/0x24
>>   i3c_device_get_info+0x24/0x58
>>   i3c_device_uevent+0x34/0xa4
>>   dev_uevent+0x310/0x384
>>   kobject_uevent_env+0x244/0x414
>>   kobject_uevent+0x14/0x20
>>   device_add+0x278/0x460
>>   device_register+0x20/0x34
>>   i3c_master_register_new_i3c_devs+0x78/0x154
>>   i3c_master_register+0x6a0/0x6d4
>>   mtk_i3c_master_probe+0x3b8/0x4d8
>>   platform_probe+0xa0/0xe0
>>   really_probe+0x114/0x454
>>   __driver_probe_device+0xa0/0x15c
>>   driver_probe_device+0x3c/0x1ac
>>   __driver_attach+0xc4/0x1f0
>>   bus_for_each_dev+0x104/0x160
>>   driver_attach+0x24/0x34
>>   bus_add_driver+0x14c/0x294
>>   driver_register+0x68/0x104
>>   __platform_driver_register+0x20/0x30
>>   init_module+0x20/0xfe4
>>   do_one_initcall+0x184/0x464
>>   do_init_module+0x58/0x1ec
>>   load_module+0xefc/0x10c8
>>   __arm64_sys_finit_module+0x238/0x33c
>>   invoke_syscall+0x58/0x10c
>>   el0_svc_common+0xa8/0xdc
>>   do_el0_svc+0x1c/0x28
>>   el0_svc+0x50/0xac
>>   el0t_64_sync_handler+0x70/0xbc
>>   el0t_64_sync+0x1a8/0x1ac
>>
>> Signed-off-by: Defa Li <defa.li@...iatek.com>
>> ---
>>   drivers/i3c/master.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
>> index 6f3eb710a75d..bb8a8bf0c4c7 100644
>> --- a/drivers/i3c/master.c
>> +++ b/drivers/i3c/master.c
>> @@ -282,7 +282,8 @@ static int i3c_device_uevent(const struct device 
>> *dev, struct kobj_uevent_env *e
>>       struct i3c_device_info devinfo;
>>       u16 manuf, part, ext;
>>   -    i3c_device_get_info(i3cdev, &devinfo);
>> +    if (i3cdev->desc)
>> +        devinfo = i3cdev->desc->info;
> Now you have left devinfo unitialized if i3cdev->desc == NULL
> You have to figure out what to do in that case.
It looks like it is old prolem, already introduced in 2017, commit 
3a379bbcea.
There is a similar problem in modalias_show() and mctp_i3c_setup()

To be honest, I don't know the driver well enough. Maybe i3cdev->desc should
never be NULL. Perhaps we need a WARN_ON or WARN_ON_ONCE instead
of a simple NULL check. Still we need to exit the function if the unexpected
happens.
>>       manuf = I3C_PID_MANUF_ID(devinfo.pid);
>>       part = I3C_PID_PART_ID(devinfo.pid);
>>       ext = I3C_PID_EXTRA_INFO(devinfo.pid);
>