linux-kernel - Re: [PATCH] watchdog: aspeed: replace mdelay with msleep

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <927f2063-4587-423f-8c75-441f55e17671@roeck-us.net>
Date: Sat, 14 Dec 2024 13:46:36 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: David Laight <David.Laight@...LAB.COM>,
 Phil Eichinger <phil@...kapfel.net>,
 "wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
 "joel@....id.au" <joel@....id.au>,
 "andrew@...econstruct.com.au" <andrew@...econstruct.com.au>,
 "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] watchdog: aspeed: replace mdelay with msleep

On 12/14/24 13:21, David Laight wrote:
> From: Guenter Roeck
>> Sent: 12 December 2024 13:56
>> To: Phil Eichinger <phil@...kapfel.net>; wim@...ux-watchdog.org; joel@....id.au;
>> andrew@...econstruct.com.au; linux-watchdog@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
>> linux-aspeed@...ts.ozlabs.org; linux-kernel@...r.kernel.org
>> 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@...kapfel.net>
>>> ---
>>>    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