Re: [PATCH] ipmi: Add timeout to unconditional wait in __get_device_id()

[Tony Camuso]

On 4/15/26 5:22 PM, Frederick Lawler wrote:
> Hi Corey & Tony,
>
> On Wed, Apr 15, 2026 at 11:46:27AM -0400, 'Tony Camuso' via kernel-team wrote:
> > On Wed, Apr 15, 2026 at 12:59:30PM +0100, Matt Fleming wrote:
> > > From: Matt Fleming <mfl...@cl...>
> > >
> > > When the BMC does not respond to a "Get Device ID" command, the
> > > wait_event() in __get_device_id() blocks forever in
> > > TASK_UNINTERRUPTIBLE while holding bmc->dyn_mutex. Every subsequent
> > > sysfs reader then piles up in D state. Replace with
> > > wait_event_timeout() to return -EIO after 1 second.
> >
> > On Wed, Apr 15, 2026 at 12:17:04PM, Corey Minyard wrote:
> > > This is the second report I have of something like this.  So
> > > something is up.  I'm adding Tony, who reported something like this
> > > dealing with the watchdog.
> > >
> > > The lower level driver should never not return an answer, it is
> > > supposed to guarantee that it returns an error if the BMC doesn't
> > > respond. So the bug is not here, the bug is elsewhere.
>
> This is a bit of a throwback to our previous discussions around [1].
>
> I did end up applying [2] based on that discussion, and had limited
> success, but we still have external resets that cause us to enter
> this undesirable state :(

In my testing with updates from the Linus tree, after a BMC cold reset:
  1. The KCS driver returned -EBUSY to callers (good)
  2. The watchdog daemon received the error and initiated shutdown
  3. No D-state hang

My tests, conducted on a Dell PER640, verified that Corey's upstream fixes
cause the driver to properly return errors instead of blocking.
At least on that platform.

Which hich low-level driver are you using (KCS, BT, SSIF)?
The PER640 uses KCS.
# cat /sys/class/ipmi/ipmi0/device/params 2>/dev/null
kcs,i/o,0xca8,rsp=4,rsi=1,rsh=0,irq=10,ipmb=32

> [1]: https://lore.kernel.org/all/aJUMlAG17c6lCgFq@xxxxxxxxxxxxxxxx/
> [2]: https://lore.kernel.org/all/20250807230648.1112569-2-corey@xxxxxxxxxxx/
> > I've been tracking a related issue (RHEL customer case) where BMC
> > reset while the IPMI watchdog is active causes D-state hangs. This
> > appears to be the same root cause Matt is hitting.
> >
> > I backported the recent upstream KCS/SI fixes to a RHEL 9 test kernel
> > (54 patches bringing it to mainline parity) and tested today on a
> > Dell R640.
>
> I assume this patch series: "ipmi:watchdog: Fix panic, D-state hang, and
> lost protection on BMC reset" [3]?
>
> [3]: https://lore.kernel.org/all/20260407175134.3367345-1-tcamuso@xxxxxxxxxx/

Actually, no. The 54 commits I backported simply bring my RHEL-9 test kernel
to parity with the Linus tree, which includes [2] and ...
cae66f1a1dcd 2026-02-13 corey@xxxxxxxxxxx ipmi:si: Fix check for a misbehaving BMC