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Wed, 15 Apr 2026 08:46:31 -0700 (PDT) Received: from [192.168.3.252] ([74.75.144.57]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50e1b016a2asm18416401cf.31.2026.04.15.08.46.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Apr 2026 08:46:29 -0700 (PDT) Message-ID: <9b6af9ab-79f9-4f87-ab7c-8ad6efeb18ed@redhat.com> Date: Wed, 15 Apr 2026 11:46:27 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ipmi: Add timeout to unconditional wait in __get_device_id() To: corey@minyard.net, Matt Fleming Cc: openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, kernel-team@cloudflare.com, Matt Fleming References: <20260415115930.3428942-1-matt@readmodwrite.com> Content-Language: en-US From: Tony Camuso In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On Wed, Apr 15, 2026 at 12:59:30PM +0100, Matt Fleming wrote: > From: Matt Fleming > > 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. 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. Test: Trigger `ipmitool mc reset cold` while watchdog daemon is running. Results with backported fixes: [ 245.376402] IPMI Watchdog: heartbeat completion received [ 246.376392] IPMI Watchdog: heartbeat send failure: -16 [ 247.377560] IPMI Watchdog: heartbeat send failure: -16 ... [ 252.413240] IPMI Watchdog: set timeout error: -16 The watchdog daemon received error 16 (EBUSY) and eventually initiated orderly shutdown: write watchdog device gave error 16 = 'Device or resource busy' shutting down the system because of error 16 Key finding: With the upstream fixes, the driver returns -EBUSY instead of blocking forever. No D-state hang. The watchdog daemon handles the error and initiates orderly reboot. Note: There was still a delay of several minutes before the daemon timed out and triggered shutdown. The driver returned errors promptly, but the watchdog daemon's retry logic (error retry time-out = 120 seconds) extended the overall recovery time. This may warrant a separate look at whether the daemon's retry behavior is appropriate when the BMC is completely unresponsive. This confirms Corey's assessment - the bug is in the lower-level driver not returning errors, not in __get_device_id(). Matt's timeout patch would be a defensive fallback, but the real fix is ensuring KCS/SI properly returns errors when the BMC is unresponsive. Tony