linux-kernel - Re: watchdog: pcf2127: systemd fails on 5.11

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Message-ID: <20210224152529.GA242356@roeck-us.net>
Date:   Wed, 24 Feb 2021 07:25:29 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Bruno Thomsen <bruno.thomsen@...il.com>,
        linux-watchdog@...r.kernel.org, linux-rtc@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Lars Alex Pedersen <laa@...strup.com>,
        Bruno Thomsen <bth@...strup.com>,
        NXP Linux Team <linux-imx@....com>
Subject: Re: watchdog: pcf2127: systemd fails on 5.11

On Wed, Feb 24, 2021 at 04:00:14PM +0100, Alexandre Belloni wrote:
> Hi,
> 
> On 24/02/2021 15:55:00+0100, Bruno Thomsen wrote:
> > You could be right about that, I don't think the watchdog feature should
> > be available for use if the alarm feature is enabled due to how CTRL2
> > register behaves.
> > 
> > The hardware I am testing on is a custom board, but it's actually
> > possible to get a Raspberry Pi module called RasClock that has
> > the chip.
> > 
> 
> I have an eval board for the PCF2127 (and PCF2129), the OM13513.
> 
> > I will test some locking around WD_VAL register access as that is used
> > in pcf2127_wdt_ping function.
> > 
> > My initial test shows that spin_lock_irqsave around regmap calls are not
> > a good idea as it result in:
> > BUG: scheduling while atomic: watchdog/70/0x00000002
> > BUG: scheduling while atomic: systemd/1/0x00000002
> > 
> 
> The issue is not only regmap but the fact that i2C and spi accesses are
> allowed to sleep.
> 
Correct, those would have to be mutexes.

Thanks,
Guenter