RE: [外部邮件] Re: [PATCH][v2] hung_task: Panic after fixed number of hung tasks

["Li,Rongqing" <lirongqing@baidu.com>]

> On 2025/9/28 13:31, lirongqing wrote:
> > From: Li RongQing <lirongqing@baidu.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.
> >
> > Acked-by: Lance Yang <lance.yang@linux.dev>
> > Signed-off-by: Li RongQing <lirongqing@baidu.com>
> > ---
> 
> It's working as expect. So:
> Tested-by: Lance Yang <lance.yang@linux.dev>
> 
> But on second thought: regarding this new sysctl parameter, I was wondering if
> a name like max_hung_task_count_to_panic might be a bit more explicit, just to
> follow the convention from max_rcu_stall_to_panic.
> 

I see that all the hung task sysctl parameters start with "hung_task"? Should we keep this convention? If so, we could name it "hung_task_max_to_panic". If not, we could call it "max_hang_task_to_panic"?

-Li


> No strong opinion on this, though :)
> 
> Cheers,
> Lance
> 
> > Diff with v1: change documentation as Lance suggested
> >
> >   Documentation/admin-guide/sysctl/kernel.rst |  8 ++++++++
> >   kernel/hung_task.c                          | 14 +++++++++++++-
> >   2 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/sysctl/kernel.rst
> > b/Documentation/admin-guide/sysctl/kernel.rst
> > index 8b49eab..98b47a7 100644
> > --- a/Documentation/admin-guide/sysctl/kernel.rst
> > +++ b/Documentation/admin-guide/sysctl/kernel.rst
> > @@ -405,6 +405,14 @@ 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, 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.
> >
> >   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;
> > +
> >   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),