Re: Faulty commit "watchdog: iTCO_wdt: Account for rebooting on second timeout"

From: Greg KH
Date: Fri Aug 06 2021 - 02:28:56 EST

On Tue, Aug 03, 2021 at 04:51:08PM +0200, Jean Delvare wrote:
> Hi all,
> Commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on
> second timeout") causes a regression on several systems. Symptoms are:
> system reboots automatically after a short period of time if watchdog
> is enabled (by systemd for example). This has been reported in bugzilla:
> Unfortunately this commit was backported to all stable kernel branches
> (4.14, 4.19, 5.4, 5.10, 5.12 and 5.13). I'm not sure why that is the
> case, BTW, as there is no Fixes tag and no Cc to stable@vger either.
> And the fix is not trivial, has apparently not seen enough testing,
> and addresses a problem that has a known and simple workaround. IMHO it
> should never have been accepted as a stable patch in the first place.
> Especially when the previous attempt to fix this issue already ended
> with a regression and a revert.
> Anyway... After a glance at the patch, I see what looks like a nice
> thinko:
> + if (p->smi_res &&
> + (SMI_EN(p) & (TCO_EN | GBL_SMI_EN)) != (TCO_EN | GBL_SMI_EN))
> The author most certainly meant inl(SMI_EN(p)) (the register's value)
> and not SMI_EN(p) (the register's address).

Let me go revert this from the stable trees now, thanks for the report.

greg k-h