From: Andrew Morton <akpm@linux-foundation.org>
To: Lance Yang <ioworker0@gmail.com>
Cc: will@kernel.org, peterz@infradead.org, mingo@redhat.com,
longman@redhat.com, mhiramat@kernel.org,
anna.schumaker@oracle.com, boqun.feng@gmail.com,
joel.granados@kernel.org, kent.overstreet@linux.dev,
leonylgao@tencent.com, linux-kernel@vger.kernel.org,
rostedt@goodmis.org, senozhatsky@chromium.org,
tfiga@chromium.org, amaindex@outlook.com, jstultz@google.com,
Mingzhe Yang <mingzhe.yang@ly.com>
Subject: Re: [PATCH v4 2/3] hung_task: show the blocker task if the task is hung on semaphore
Date: Mon, 7 Apr 2025 13:08:36 -0700 [thread overview]
Message-ID: <20250407130836.5e52ab2aa2e77c67f890637b@linux-foundation.org> (raw)
In-Reply-To: <20250320064923.24000-3-ioworker0@gmail.com>
On Thu, 20 Mar 2025 14:49:22 +0800 Lance Yang <ioworker0@gmail.com> wrote:
> Inspired by mutex blocker tracking[1], this patch makes a trade-off to
> balance the overhead and utility of the hung task detector.
>
> Unlike mutexes, semaphores lack explicit ownership tracking, making it
> challenging to identify the root cause of hangs. To address this, we
> introduce a last_holder field to the semaphore structure, which is
> updated when a task successfully calls down() and cleared during up().
>
> The assumption is that if a task is blocked on a semaphore, the holders
> must not have released it. While this does not guarantee that the last
> holder is one of the current blockers, it likely provides a practical hint
> for diagnosing semaphore-related stalls.
>
> With this change, the hung task detector can now show blocker task's info
> like below:
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
+#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
It looks pretty simple to reduce the amount of ifdeffery which this
patch adds.
next prev parent reply other threads:[~2025-04-07 20:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-20 6:49 [PATCH v4 0/3] hung_task: extend blocking task stacktrace dump to semaphore Lance Yang
2025-03-20 6:49 ` [PATCH v4 1/3] hung_task: replace blocker_mutex with encoded blocker Lance Yang
2025-04-07 20:08 ` Andrew Morton
2025-04-08 12:29 ` Lance Yang
2025-03-20 6:49 ` [PATCH v4 2/3] hung_task: show the blocker task if the task is hung on semaphore Lance Yang
2025-04-07 20:08 ` Andrew Morton [this message]
2025-04-07 20:08 ` Andrew Morton
2025-04-08 12:27 ` Lance Yang
2025-03-20 6:49 ` [PATCH v4 3/3] samples: extend hung_task detector test with semaphore support Lance Yang
2025-04-07 20:08 ` [PATCH v4 0/3] hung_task: extend blocking task stacktrace dump to semaphore Andrew Morton
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