linux-kernel - Re: [PATCH v2] serial: imx: Use uart_port_lock_irq() instead of uart_port

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Message-ID: <b092fdec6fda26c56b4f2cc5927bbaa4a6d786f9.camel@pengutronix.de>
Date: Tue, 10 Dec 2024 10:00:57 +0100
From: Lucas Stach <l.stach@...gutronix.de>
To: Xiaolei Wang <xiaolei.wang@...driver.com>, gregkh@...uxfoundation.org, 
 jirislaby@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de, 
 kernel@...gutronix.de, festevam@...il.com, esben@...nix.com, marex@...x.de,
  ilpo.jarvinen@...ux.intel.com, linux@...musvillemoes.dk, 
 stefan.eichenberger@...adex.com, l.sanfilippo@...bus.com, 
 cniedermaier@...electronics.com, rickaran@...s.com
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, 
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] serial: imx: Use uart_port_lock_irq() instead of
 uart_port_lock()

Am Dienstag, dem 10.12.2024 um 11:42 +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_irq() 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@...driver.com>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
> 
> v1:
>   https://patchwork.kernel.org/project/linux-arm-kernel/patch/20241209124732.693834-1-xiaolei.wang@windriver.com/
> v2:
>   use uart_port_lock_irq() instead of uart_port_lock_irqsave()
> 
>  drivers/tty/serial/imx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 17f70e4bee43..9c59ec128bb4 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -2692,7 +2692,7 @@ static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
>  {
>  	u32 ucr3;
>  
> -	uart_port_lock(&sport->port);
> +	uart_port_lock_irq(&sport->port);
>  
>  	ucr3 = imx_uart_readl(sport, UCR3);
>  	if (on) {
> @@ -2714,7 +2714,7 @@ 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_irq(&sport->port);
>  }
>  
>  static int imx_uart_suspend_noirq(struct device *dev)