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Message-ID: <819fbfed27cf4e57860645f9edc774a3@baidu.com>
Date: Sun, 28 Sep 2025 03:19:58 +0000
From: "Li,Rongqing" <lirongqing@...du.com>
To: Lance Yang <lance.yang@...ux.dev>
CC: "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"arnd@...db.de" <arnd@...db.de>, "joel.granados@...nel.org"
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<rostedt@...dmis.org>, "pawan.kumar.gupta@...ux.intel.com"
<pawan.kumar.gupta@...ux.intel.com>, "akpm@...ux-foundation.org"
<akpm@...ux-foundation.org>, "dave.hansen@...ux.intel.com"
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"mhiramat@...nel.org" <mhiramat@...nel.org>
Subject: RE: [外部邮件] Re: [PATCH] hung_task: Panic after fixed number of hung tasks
> -----Original Message-----
> From: Lance Yang <lance.yang@...ux.dev>
> Sent: 2025年9月27日 10:39
> To: Li,Rongqing <lirongqing@...du.com>
> Cc: linux-doc@...r.kernel.org; linux-kernel@...r.kernel.org; arnd@...db.de;
> joel.granados@...nel.org; feng.tang@...ux.alibaba.com; pauld@...hat.com;
> kees@...nel.org; rostedt@...dmis.org; pawan.kumar.gupta@...ux.intel.com;
> akpm@...ux-foundation.org; dave.hansen@...ux.intel.com; mingo@...nel.org;
> paulmck@...nel.org; corbet@....net; mhiramat@...nel.org
> Subject: [外部邮件] Re: [PATCH] hung_task: Panic after fixed number of hung
> tasks
>
>
>
> On 2025/9/25 14:06, lirongqing wrote:
> > From: Li RongQing <lirongqing@...du.com>
> >
> > Currently, when hung_task_panic is enabled, kernel will panic
> > immediately upon detecting the first hung task. However, some hung
> > tasks are transient and the system can recover fully, while others are
> > unrecoverable and trigger consecutive hung task reports, and a panic is
> expected.
> >
> > This commit adds a new sysctl parameter hung_task_count_to_panic to
> > allows specifying the number of consecutive hung tasks that must be
> > detected before triggering a kernel panic. This provides finer control
> > for environments where transient hangs maybe happen but persistent
> > hangs should still be fatal.
> >
> > Signed-off-by: Li RongQing <lirongqing@...du.com>
> > ---
> > Documentation/admin-guide/sysctl/kernel.rst | 6 ++++++
> > kernel/hung_task.c | 14 +++++++++++++-
> > 2 files changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/sysctl/kernel.rst
> > b/Documentation/admin-guide/sysctl/kernel.rst
> > index 8b49eab..4240e7b 100644
> > --- a/Documentation/admin-guide/sysctl/kernel.rst
> > +++ b/Documentation/admin-guide/sysctl/kernel.rst
> > @@ -405,6 +405,12 @@ This file shows up if
> ``CONFIG_DETECT_HUNG_TASK`` is enabled.
> > 1 Panic immediately.
> > = =================================================
> >
> > +hung_task_count_to_panic
> > +=====================
> > +
> > +When set to a non-zero value, after the number of consecutive hung
> > +task occur, the kernel will triggers a panic
>
> Hmm... the documentation here seems a bit misleading.
>
> hung_task_panic=1 will always cause an immediate panic, regardless of the
> hung_task_count_to_panic setting, right?
>
> Perhaps something like this would be more accurate?
>
> ```
> hung_task_count_to_panic
> ========================
>
> When set to a non-zero value, a kernel panic will be triggered if the number of
> detected hung tasks reaches this value.
>
> Note that setting hung_task_panic=1 will still cause an immediate panic on the
> first hung task, overriding this setting.
> ```
>
> >
> > hung_task_check_count
> > =====================
> > diff --git a/kernel/hung_task.c b/kernel/hung_task.c index
> > 8708a12..87a6421 100644
> > --- a/kernel/hung_task.c
> > +++ b/kernel/hung_task.c
> > @@ -83,6 +83,8 @@ static unsigned int __read_mostly
> sysctl_hung_task_all_cpu_backtrace;
> > static unsigned int __read_mostly sysctl_hung_task_panic =
> > IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC);
> >
> > +static unsigned int __read_mostly sysctl_hung_task_count_to_panic;
>
> Nit: while static variables are guaranteed to be zero-initialized, it's a good
> practice and clearer for readers to initialize them explicitly.
>
> static unsigned int __read_mostly sysctl_hung_task_count_to_panic = 0;
>
>
./scripts/checkpatch.pl reports error when initialise statics to 0, so I will keep it uninitialized
ERROR: do not initialise statics to 0
#51: FILE: kernel/hung_task.c:86:
+static unsigned int __read_mostly sysctl_hung_task_count_to_panic = 0;
thanks
-Li
> Otherwise, this patch looks good to me!
> Acked-by: Lance Yang <lance.yang@...ux.dev>
>
> > +
> > static int
> > hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
> > {
> > @@ -219,7 +221,9 @@ static void check_hung_task(struct task_struct *t,
> > unsigned long timeout)
> >
> > trace_sched_process_hang(t);
> >
> > - if (sysctl_hung_task_panic) {
> > + if (sysctl_hung_task_panic ||
> > + (sysctl_hung_task_count_to_panic &&
> > + (sysctl_hung_task_detect_count >=
> > +sysctl_hung_task_count_to_panic))) {
> > console_verbose();
> > hung_task_show_lock = true;
> > hung_task_call_panic = true;
> > @@ -388,6 +392,14 @@ static const struct ctl_table hung_task_sysctls[] = {
> > .extra2 = SYSCTL_ONE,
> > },
> > {
> > + .procname = "hung_task_count_to_panic",
> > + .data = &sysctl_hung_task_count_to_panic,
> > + .maxlen = sizeof(int),
> > + .mode = 0644,
> > + .proc_handler = proc_dointvec_minmax,
> > + .extra1 = SYSCTL_ZERO,
> > + },
> > + {
> > .procname = "hung_task_check_count",
> > .data = &sysctl_hung_task_check_count,
> > .maxlen = sizeof(int),
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