Re: [PATCH] i3c: Remove redundant lock in i3c_device_uevent

Frank Li
2024-10-31T20:54:05Z

Your patch have not remove "lock", just use cached data i3cdev->desc->info
instead of call i3c_device_get_info().

So title should like

Use i3cdev->desc->info instead of call i3c_device_get_info() to avoid deadlock

On Tue, Oct 29, 2024 at 10:09:40AM +0800, mtk25126 wrote:
> We encountered the following lockdep warning.
> The i3c_master_register function recursively acquires &i3cbus->lock twice,
> which may cause a deadlock.

A deadlock may happen since the i3c_master_register() acquires
&i3cbus->lock twice. See below log.

According to your dump message, it should happen every time.
>
> Remove the logic of obtaining i3cbus->lock when using the i3c_device_uevent
> function to obtain the i3c_device_info structure.

Use i3cdev->desc->info instead of call i3c_device_info() to avoid lock
twice.

>
> ============================================
> 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: mtk25126 <defa.li@mediatek.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;
> manuf = I3C_PID_MANUF_ID(devinfo.pid);
> part = I3C_PID_PART_ID(devinfo.pid);
> ext = I3C_PID_EXTRA_INFO(devinfo.pid);
> --
> 2.46.0
>
>
> --
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