From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C82991F76B6 for ; Thu, 13 Mar 2025 22:29:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741904995; cv=none; b=ZU6Kgw4F+PgSTlTflYiiwsIKLtSMxBVTA2EzublyGVFHWif1bwyeibGKlj3VAHwK7h3ifV++VVathSOUoxc3Nzp3lTyioCMOH8kxjcvZjFzHYWT4p1+5comPfHh5wN/W6mb/BrcKfpEeyKZtFNEQW9Q7SjV2D7W2T4MNsESSZaI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741904995; c=relaxed/simple; bh=r5HlNhWjHCKaJ1PLGw/JuQyEXvr29jUDRW2niBXyrB0=; h=Date:To:From:Subject:Message-Id; b=lduRM446Q5Kaxw1DRrWiW0lrDjfF0t/DBTdfquNa4QzBoAZI4JJ1Gcus8HywMHp+FRUZcT11sZJrLQAdLyKeurtev/Wgo14Iby2uvv3DJZAeAFpkpFRz++OIGS0r3Kwu38fW77b1cZejtMXBPs0PBMbMNRYBvpygucnBF1ozRKs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=cYsW/HMZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="cYsW/HMZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30874C4CEEA; Thu, 13 Mar 2025 22:29:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1741904995; bh=r5HlNhWjHCKaJ1PLGw/JuQyEXvr29jUDRW2niBXyrB0=; h=Date:To:From:Subject:From; b=cYsW/HMZ7p8+jcoDXvnpz48AcsuKl48WGgW5Dikmw9Lb8/kXGJEgGNnBX0qC4H2gD PWAIOBrc2ShbX+LE6gZ+fMiYJLGvJwv1eciihqn4p/3w9/FZMMPwjiR+AFPU+VYKTn 1NWrYNySEpEE97gCxVkblE/ecIH1sPGGE/2punWU= Date: Thu, 13 Mar 2025 15:29:54 -0700 To: mm-commits@vger.kernel.org,will@kernel.org,tfiga@chromium.org,senozhatsky@chromium.org,rostedt@goodmis.org,mingo@redhat.com,longman@redhat.com,leonylgao@tencent.com,kent.overstreet@linux.dev,joel.granados@kernel.org,ioworker0@gmail.com,boqun.feng@gmail.com,anna.schumaker@oracle.com,mhiramat@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + samples-add-hung_task-detector-mutex-blocking-sample.patch added to mm-nonmm-unstable branch Message-Id: <20250313222955.30874C4CEEA@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: samples: add hung_task detector mutex blocking sample has been added to the -mm mm-nonmm-unstable branch. Its filename is samples-add-hung_task-detector-mutex-blocking-sample.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/samples-add-hung_task-detector-mutex-blocking-sample.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Masami Hiramatsu (Google) Subject: samples: add hung_task detector mutex blocking sample Date: Tue, 25 Feb 2025 16:02:43 +0900 Add a hung_task detector mutex blocking test sample code. This module will create a dummy file on the debugfs. That file will cause the read process to sleep for enough long time (256 seconds) while holding a mutex. As a result, the second process will wait on the mutex for a prolonged duration and be detected by the hung_task detector. Usage is; > cd /sys/kernel/debug/hung_task > cat mutex & cat mutex and wait for hung_task message. Link: https://lkml.kernel.org/r/174046696281.2194069.4567490148001547311.stgit@mhiramat.tok.corp.google.com Signed-off-by: Masami Hiramatsu (Google) Cc: Anna Schumaker Cc: Boqun Feng Cc: Ingo Molnar Cc: Joel Granados Cc: Kent Overstreet Cc: Lance Yang Cc: Sergey Senozhatsky Cc: Steven Rostedt Cc: Tomasz Figa Cc: Waiman Long Cc: Will Deacon Cc: Yongliang Gao Signed-off-by: Andrew Morton --- samples/Kconfig | 9 +++ samples/Makefile | 1 samples/hung_task/Makefile | 2 samples/hung_task/hung_task_mutex.c | 66 ++++++++++++++++++++++++++ 4 files changed, 78 insertions(+) diff --git a/samples/hung_task/hung_task_mutex.c a/samples/hung_task/hung_task_mutex.c new file mode 100644 --- /dev/null +++ a/samples/hung_task/hung_task_mutex.c @@ -0,0 +1,66 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * hung_task_mutex.c - Sample code which causes hung task by mutex + * + * Usage: load this module and read `/hung_task/mutex` + * by 2 or more processes. + * + * This is for testing kernel hung_task error message. + * Note that this will make your system freeze and maybe + * cause panic. So do not use this except for the test. + */ + +#include +#include +#include +#include +#include + +#define HUNG_TASK_DIR "hung_task" +#define HUNG_TASK_FILE "mutex" +#define SLEEP_SECOND 256 + +static const char dummy_string[] = "This is a dummy string."; +static DEFINE_MUTEX(dummy_mutex); +struct dentry *hung_task_dir; + +static ssize_t read_dummy(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) +{ + /* If the second task waits on the lock, it is uninterruptible sleep. */ + guard(mutex)(&dummy_mutex); + + /* When the first task sleep here, it is interruptible. */ + msleep_interruptible(SLEEP_SECOND * 1000); + + return simple_read_from_buffer(user_buf, count, ppos, + dummy_string, sizeof(dummy_string)); +} + +static const struct file_operations hung_task_fops = { + .read = read_dummy, +}; + +static int __init hung_task_sample_init(void) +{ + hung_task_dir = debugfs_create_dir(HUNG_TASK_DIR, NULL); + if (IS_ERR(hung_task_dir)) + return PTR_ERR(hung_task_dir); + + debugfs_create_file(HUNG_TASK_FILE, 0400, hung_task_dir, + NULL, &hung_task_fops); + + return 0; +} + +static void __exit hung_task_sample_exit(void) +{ + debugfs_remove_recursive(hung_task_dir); +} + +module_init(hung_task_sample_init); +module_exit(hung_task_sample_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Masami Hiramatsu"); +MODULE_DESCRIPTION("Simple sleep under mutex file for testing hung task"); diff --git a/samples/hung_task/Makefile a/samples/hung_task/Makefile new file mode 100644 --- /dev/null +++ a/samples/hung_task/Makefile @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +obj-$(CONFIG_SAMPLE_HUNG_TASK) += hung_task_mutex.o \ No newline at end of file --- a/samples/Kconfig~samples-add-hung_task-detector-mutex-blocking-sample +++ a/samples/Kconfig @@ -300,6 +300,15 @@ config SAMPLE_CHECK_EXEC demonstrate how they should be used with execveat(2) + AT_EXECVE_CHECK. +config SAMPLE_HUNG_TASK + tristate "Hung task detector test code" + depends on DETECT_HUNG_TASK && DEBUG_FS + help + Build a module which provide a simple debugfs file. If user reads + the file, it will sleep long time (256 seconds) with holding a + mutex. Thus if there are 2 or more processes read this file, it + will be detected by the hung_task watchdog. + source "samples/rust/Kconfig" source "samples/damon/Kconfig" --- a/samples/Makefile~samples-add-hung_task-detector-mutex-blocking-sample +++ a/samples/Makefile @@ -42,3 +42,4 @@ obj-$(CONFIG_SAMPLE_FPROBE) += fprobe/ obj-$(CONFIG_SAMPLES_RUST) += rust/ obj-$(CONFIG_SAMPLE_DAMON_WSSE) += damon/ obj-$(CONFIG_SAMPLE_DAMON_PRCL) += damon/ +obj-$(CONFIG_SAMPLE_HUNG_TASK) += hung_task/ _ Patches currently in -mm which might be from mhiramat@kernel.org are hung_task-show-the-blocker-task-if-the-task-is-hung-on-mutex.patch samples-add-hung_task-detector-mutex-blocking-sample.patch