From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-watchdog@vger.kernel.org,
linux-renesas-soc@vger.kernel.org,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: Re: [RFC PATCH] watchdog: renesas_wdt: don't sleep in atomic context
Date: Sat, 19 Dec 2020 18:29:52 +0100 [thread overview]
Message-ID: <20201219172952.GA15530@kunai> (raw)
In-Reply-To: <20201002164722.GA46009@roeck-us.net>
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> > Convert usleep_range() to udelay() to avoid the bug. The downside is
> > busy looping when the watchdog is started or stopped (64us or 96us in my
> > case). However, this happens rarely enough, so it seems acceptable.
> >
> > Fixes: b836005b4f95 ("watchdog: renesas_wdt: Add a few cycles delay")
> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> > ---
> >
> > We could also add a new flag in the watchdog core "IS_RESTARTING" or
> > similar and check that in the driver. Depending on the flag, we use
> > udelay() or usleep_range(). Not sure, if this is feasible or
> > over-engineered, though. Looking forward for comments.
>
> Seems to be neither to me. I don't know if there are many drivers who sleep
> in the stop function, but even if there are none (today) it would be a
> generic problem.
>
> On a side note, I am quite sure there is a system wide flag indicating
> that the system is rebooting. Maybe we can just use that ?
So, it took me a while to get back to this. Yes, we can use system_state
to determine which udelay to use. I am working on a helper for that.
However, as it turned out, this driver needs a different approach
because there were multiple issues with reusing the generic wdt-start
routine. Proper patch will come in some minutes.
Thanks for your input!
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prev parent reply other threads:[~2020-12-19 17:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-02 15:09 [RFC PATCH] watchdog: renesas_wdt: don't sleep in atomic context Wolfram Sang
2020-10-02 15:12 ` Wolfram Sang
2020-10-02 16:47 ` Guenter Roeck
2020-12-19 17:29 ` Wolfram Sang [this message]
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