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

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

> > Signed-off-by: Li RongQing <lirongqing@baidu.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.
> ```


I will rewrite this documentation as your suggestions


> 
> >
> >   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;
> 


Ok, I will change it

Thanks

-Li

> 
> Otherwise, this patch looks good to me!
> Acked-by: Lance Yang <lance.yang@linux.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),