On 03.08.21 16:51, 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:
https://bugzilla.kernel.org/show_bug.cgi?id=213809
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).
https://lkml.org/lkml/2021/7/26/349
Jan