Re: [PATCH] serial: imx: Use uart_port_lock_irqsave() instead of uart_port_lock()

[wang xiaolei <xiaolei.wang@windriver.com>]

On 12/10/24 1:37 AM, Lucas Stach wrote:
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> Am Montag, dem 09.12.2024 um 20:47 +0800 schrieb Xiaolei Wang:
>> When executing 'ehco mem > /sys/power/state', the following
>> deadlock occurs. Since there is output during the serial
>> port entering the suspend process, the suspend will be
>> interrupted, resulting in the nesting of locks. Therefore,
>> use uart_port_lock_irqsave instead of uart_port_unlock.
>>
>> WARNING: inconsistent lock state
>> 6.12.0-rc2-00002-g3c199ed5bd64-dirty #23 Not tainted
>> --------------------------------
>> inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
>> sh/494 [HC0[0]:SC0[0]:HE1:SE1] takes:
>> c4db5850 (&port_lock_key){?.-.}-{3:3}, at: imx_uart_enable_wakeup+0x14/0x254
>> {IN-HARDIRQ-W} state was registered at:
>>    lock_acquire+0x104/0x348
>>    _raw_spin_lock+0x48/0x84
>>    imx_uart_int+0x14/0x4dc
>>    __handle_irq_event_percpu+0xac/0x2fc
>>    handle_irq_event_percpu+0xc/0x40
>>    handle_irq_event+0x38/0x8c
>>    handle_fasteoi_irq+0xb4/0x1b8
>>    handle_irq_desc+0x1c/0x2c
>>    gic_handle_irq+0x6c/0xa0
>>    generic_handle_arch_irq+0x2c/0x64
>>    call_with_stack+0x18/0x20
>>    __irq_svc+0x9c/0xbc
>>    _raw_spin_unlock_irqrestore+0x2c/0x48
>>    uart_write+0xd8/0x3a0
>>    do_output_char+0x1a8/0x1e4
>>    n_tty_write+0x224/0x440
>>    file_tty_write.constprop.0+0x124/0x250
>>    do_iter_readv_writev+0x100/0x1e0
>>    vfs_writev+0xc4/0x448
>>    do_writev+0x68/0xf8
>>    ret_fast_syscall+0x0/0x1c
>> irq event stamp: 31593
>> hardirqs last  enabled at (31593): [<c1150e48>] _raw_spin_unlock_irqrestore+0x44/0x48
>> hardirqs last disabled at (31592): [<c07f32f0>] clk_enable_lock+0x60/0x120
>> softirqs last  enabled at (30334): [<c012d1d4>] handle_softirqs+0x2cc/0x478
>> softirqs last disabled at (30325): [<c012d510>] __irq_exit_rcu+0x120/0x15c
>>
>> other info that might help us debug this:
>>   Possible unsafe locking scenario:
>>
>>         CPU0
>>         ----
>>    lock(&port_lock_key);
>>    <Interrupt>
>>      lock(&port_lock_key);
>>
>> Fixes: 3c199ed5bd64 ("serial: imx: Grab port lock in imx_uart_enable_wakeup()")
>> Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
>> ---
>>   drivers/tty/serial/imx.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
>> index 17f70e4bee43..4470bcb3ef19 100644
>> --- a/drivers/tty/serial/imx.c
>> +++ b/drivers/tty/serial/imx.c
>> @@ -2691,8 +2691,9 @@ static void imx_uart_save_context(struct imx_port *sport)
>>   static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
>>   {
>>        u32 ucr3;
>> +     unsigned long flags;
>>
>> -     uart_port_lock(&sport->port);
>> +     uart_port_lock_irqsave(&sport->port, &flags);
> This function is only called from process context, so it should be fine
> to use uart_port_lock_irq().
Thank you for your reminder, Lucas, I will send a new version

thanks
xiaolei
>
> Regards,
> Lucas
>
>>        ucr3 = imx_uart_readl(sport, UCR3);
>>        if (on) {
>> @@ -2714,7 +2715,7 @@ static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
>>                imx_uart_writel(sport, ucr1, UCR1);
>>        }
>>
>> -     uart_port_unlock(&sport->port);
>> +     uart_port_unlock_irqrestore(&sport->port, flags);
>>   }
>>
>>   static int imx_uart_suspend_noirq(struct device *dev)