Re: [PATCH] watchdog: aspeed: replace mdelay with msleep

[Guenter Roeck]

On 12/14/24 13:21, David Laight wrote:
> From: Guenter Roeck
> > Sent: 12 December 2024 13:56
> > To: Phil Eichinger <phil@xxxxxxxxxxxxx>; wim@xxxxxxxxxxxxxxxxxx; joel@xxxxxxxxx;
> > andrew@xxxxxxxxxxxxxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-aspeed@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH] watchdog: aspeed: replace mdelay with msleep
> >
> > On 12/12/24 03:30, Phil Eichinger wrote:
> > > Since it is not called in an atomic context the mdelay function
> > > can be replaced with msleep to avoid busy wait.
> > >
> > > Signed-off-by: Phil Eichinger <phil@xxxxxxxxxxxxx>
> > > ---
> > >    drivers/watchdog/aspeed_wdt.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
> > > index b4773a6aaf8c..98ef341408f7 100644
> > > --- a/drivers/watchdog/aspeed_wdt.c
> > > +++ b/drivers/watchdog/aspeed_wdt.c
> > > @@ -208,7 +208,7 @@ static int aspeed_wdt_restart(struct watchdog_device *wdd,
> > >    	wdt->ctrl &= ~WDT_CTRL_BOOT_SECONDARY;
> > >    	aspeed_wdt_enable(wdt, 128 * WDT_RATE_1MHZ / 1000);
> > >
> > > -	mdelay(1000);
> > > +	msleep(1000);
> > >
> > >    	return 0;
> > >    }
> > This is a _restart_ handler. The only purpose of the delay is to wait
> > for the reset to trigger. It is not supposed to sleep.
>
> With the recent scheduler changes isn't the code likely to get
> pre-empted?
> Which (effectively) converts is to a sleep?

This code is called from do_kernel_restart(), which in turn is called from
machine_restart(). I'd think that the kernel has a severe problem if it
decides to preempt that function.

Guenter