From: ruipengqi <ruipengqi3@gmail.com>
To: akpm@linux-foundation.org, peterz@infradead.org, bigeasy@linutronix.de
Cc: lance.yang@linux.dev, mhiramat@kernel.org, pmladek@suse.com,
mingo@redhat.com, will@kernel.org, boqun@kernel.org,
longman@redhat.com, clrkwllms@kernel.org, rostedt@goodmis.org,
zhouyuhang@kylinos.cn, arnd@arndb.de, colin.i.king@gmail.com,
ebiggers@kernel.org, inux-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev, ruipengqi3@gmail.com
Subject: [PATCH 0/2] hung_task: extend blocking task stacktrace dump to rtmutex
Date: Thu, 30 Jul 2026 10:29:07 +0800 [thread overview]
Message-ID: <cover.1785376929.git.ruipengqi3@gmail.com> (raw)
From: Ruipeng Qi <ruipengqi3@gmail.com>
Currently, debug_show_blocker() only tracks mutex, semaphore and rwsem
lock types. Extend it to also cover rtmutex or rt_mutex-based
implementations locks on PREEMPT_RT, so that when a task is hung
on an rtmutex, the hung task detector can identify and report which
task holds the lock.
On 64-bit systems, lock pointers are 8-byte aligned, so their three
least significant bits are always zero. Use these bits to encode the
blocker type.
Unlike semaphores, rtmutex has built-in owner tracking via lock->owner,
so no additional bookkeeping is needed. The owner can be read with
rt_mutex_owner().
With this change, the hung task detector can now show blocker task's
info like below:
[ 3000.899985] INFO: task cat:195 blocked for more than 120 seconds.
[ 3000.900561] Not tainted 7.2.0-rc4-00366-gf339a6eb59f3-dirty #22
[ 3000.900930] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 3000.901376] task:cat state:D stack:13784 pid:195 tgid:195 ppid:1 task_flags:0x400000 flags:0x00080000
[ 3000.902081] Call Trace:
[ 3000.902233] <TASK>
[ 3000.902383] __schedule+0x514/0xf50
[ 3000.902677] rt_mutex_schedule+0x1b/0x30
[ 3000.902916] rt_mutex_slowlock_block.constprop.0+0x3b/0x1c0
[ 3000.903242] __rt_mutex_slowlock_locked.constprop.0+0xa8/0x200
[ 3000.903716] rt_mutex_slowlock.constprop.0+0x48/0xb0
[ 3000.904023] rt_mutex_lock+0x32/0x40
[ 3000.904249] read_dummy_rtmutex+0x2a/0x60 [hung_task_tests]
[ 3000.904647] full_proxy_read+0x5b/0x90
[ 3000.904843] vfs_read+0xb0/0x370
[ 3000.905051] ? vm_mmap_pgoff+0xf1/0x1b0
[ 3000.905293] ? vm_mmap_pgoff+0x122/0x1b0
[ 3000.905684] ksys_read+0x68/0xe0
[ 3000.905980] do_syscall_64+0xf9/0x540
[ 3000.906213] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 3000.906643] RIP: 0033:0x49a182
[ 3000.906844] RSP: 002b:00007ffc431f6528 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 3000.907251] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000049a182
[ 3000.907673] RDX: 0000000000010000 RSI: 00007f69b2166000 RDI: 0000000000000003
[ 3000.908044] RBP: 00007f69b2166000 R08: 00000000ffffffff R09: 0000000000000000
[ 3000.908485] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000010000
[ 3000.908816] R13: 0000000000000003 R14: 0000000000000001 R15: 0000000001000000
[ 3000.909206] </TASK>
[ 3000.909351] INFO: task cat:195 is blocked on a rtmutex likely owned by task cat:194.
[ 3000.909832] task:cat state:S stack:13784 pid:194 tgid:194 ppid:1 task_flags:0x400000 flags:0x00080000
[ 3000.910426] Call Trace:
[ 3000.910618] <TASK>
[ 3000.910727] __schedule+0x514/0xf50
[ 3000.910912] schedule+0x22/0xa0
[ 3000.911064] schedule_timeout+0x81/0x100
[ 3000.911254] ? __pfx_process_timeout+0x10/0x10
[ 3000.911522] msleep_interruptible+0x28/0x50
[ 3000.911754] read_dummy_rtmutex+0x34/0x60 [hung_task_tests]
[ 3000.912019] full_proxy_read+0x5b/0x90
[ 3000.912212] vfs_read+0xb0/0x370
[ 3000.912378] ? vm_mmap_pgoff+0xf1/0x1b0
[ 3000.912630] ? vm_mmap_pgoff+0x122/0x1b0
[ 3000.912839] ksys_read+0x68/0xe0
[ 3000.913007] do_syscall_64+0xf9/0x540
[ 3000.913187] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 3000.913461] RIP: 0033:0x49a182
[ 3000.913618] RSP: 002b:00007ffd0b4cf048 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 3000.913972] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000049a182
[ 3000.914294] RDX: 0000000000010000 RSI: 00007fbf49a0d000 RDI: 0000000000000003
[ 3000.914648] RBP: 00007fbf49a0d000 R08: 00000000ffffffff R09: 0000000000000000
[ 3000.914955] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000010000
[ 3000.915208] R13: 0000000000000003 R14: 0000000000000001 R15: 0000000001000000
[ 3000.915439] </TASK>
Ruipeng Qi (2):
hung_task: show the blocker task if the task is hung on rtmutex
samples: enhance hung_task detector test with rtmutex support
include/linux/hung_task.h | 31 +++++++++++++-----
kernel/hung_task.c | 22 +++++++++++++
kernel/locking/mutex.c | 4 +--
kernel/locking/rtmutex.c | 13 ++++++++
kernel/locking/rwsem.c | 8 ++---
kernel/locking/semaphore.c | 4 +--
lib/Kconfig.debug | 1 -
samples/Kconfig | 2 +-
samples/hung_task/hung_task_tests.c | 50 ++++++++++++++++++++++++++---
9 files changed, 113 insertions(+), 22 deletions(-)
--
2.25.1
next reply other threads:[~2026-07-30 2:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-30 2:29 ruipengqi [this message]
2026-07-30 2:29 ` [PATCH 1/2] hung_task: show the blocker task if the task is hung on rtmutex ruipengqi
2026-07-30 2:50 ` Zhan Xusheng
2026-07-30 2:29 ` [PATCH 2/2] samples: enhance hung_task detector test with rtmutex support ruipengqi
2026-07-30 5:06 ` [PATCH 0/2] hung_task: extend blocking task stacktrace dump to rtmutex Lance Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cover.1785376929.git.ruipengqi3@gmail.com \
--to=ruipengqi3@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=bigeasy@linutronix.de \
--cc=boqun@kernel.org \
--cc=clrkwllms@kernel.org \
--cc=colin.i.king@gmail.com \
--cc=ebiggers@kernel.org \
--cc=inux-kernel@vger.kernel.org \
--cc=lance.yang@linux.dev \
--cc=linux-rt-devel@lists.linux.dev \
--cc=longman@redhat.com \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=will@kernel.org \
--cc=zhouyuhang@kylinos.cn \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.