Re: [PATCH 1/2] hung_task: Consolidate hung task warning into an atomic log block

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Dec 09, 2025 at 01:12:14PM +0800, Lance Yang wrote:
> 
> 
> On 2025/12/9 12:12, Aaron Tomlin wrote:
> > Consolidate the multi-line console output in check_hung_task() into a new
> > helper function, hung_task_diagnostics().
> > 
> > This patch ensures the entire diagnostic block (task info, kernel
> > version, and sysctl advice) is logged to the ring buffer via a single
> > pr_err() call. This is critical in a concurrent environment to prevent
> > message lines from interleaving with other CPU activity, thus
> > maintaining contextual integrity of the warning message.
> > 
> > Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
> > ---
> >   kernel/hung_task.c | 37 +++++++++++++++++++++++++++----------
> >   1 file changed, 27 insertions(+), 10 deletions(-)
> > 
> > diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> > index d2254c91450b..d5109a0994c5 100644
> > --- a/kernel/hung_task.c
> > +++ b/kernel/hung_task.c
> > @@ -223,6 +223,32 @@ static inline void debug_show_blocker(struct task_struct *task, unsigned long ti
> >   }
> >   #endif
> > +/**
> > + * hung_task_diagnostics - Print structured diagnostic info for a hung task.
> > + * @t: The struct task_struct of the detected hung task.
> > + *
> > + * This function consolidates the printing of core diagnostic information
> > + * for a task found to be blocked. This approach ensures atomic logging
> > + * of the multi-line message block, preventing interleaving by other
> > + * console activity, thus maintaining contextual clarity.
> > + */
> > +static void hung_task_diagnostics(struct task_struct *t)
> > +{
> > +	unsigned long blocked_secs = (jiffies - t->last_switch_time) / HZ;
> > +
> > +	pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n"
> > +	       "      %s %s %.*s\n"
> > +	       "%s\n"
> 
> "%s\n" forces an unconditional newline, causing a spurious blank line when
> the flag isn't set, right?

The first \n should not be there, this should be all one line.

If you have multiple lines wanting to be printed, use multiple pr_err()
calls.

thanks,

greg k-h