From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> Sent: Wednesday, November 11, 2020 4:31 AM
> On Mon, Nov 09, 2020 at 05:14:03PM +0800, Fugang Duan wrote:
> > For below code, there has chance to cause deadlock in SMP system:
> > Thread 1:
> > clk_enable_lock();
> > pr_info("debug message");
> > clk_enable_unlock(flags);
>
> flags?
Will remove it, thanks.
>
> >
> > Thread 2:
> > imx_uart_console_write()
> > clk_enable()
> > clk_enable_lock();
> >
> > Thread 1:
> > Acuired clk enable_lock -> printk -> console_trylock_spinning Thread
> > 2:
> > console_unlock() -> imx_uart_console_write -> clk_disable -> Acquite
> > clk enable_lock
> >
> > So the patch is to keep console port clocks always on like other
> > console drivers.
> >
> > Signed-off-by: Fugang Duan <fugang.duan@xxxxxxx>
>
> Depending on how old this problem is, identifying the commit that introduces
> the problem (and noting it in a Fixes: line) would be good.
>
In normal boot, there has no problem since there have no printk
between clk_enable_lock() and clk_enable_unlock(). If you add debug
message between them or enable track in clk driver, the issue should be
triggered.
Will add the Fixes tag in v2, thanks.
> Best regards
> Uwe
>
> --
> Pengutronix e.K. | Uwe Kleine-König
> |
> Industrial Linux Solutions | https://www.pengutronix.de/ |
