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Howlett" , linux-doc@vger.kernel.org, David Hildenbrand , Randy Dunlap , Stanislav Fomichev , linux-aspeed@lists.ozlabs.org, Andrew Jeffery , Joel Stanley , Russell King , Lorenzo Stoakes , Shuah Khan , Steven Rostedt , Jonathan Corbet , Joel Granados , Andrew Morton , Phil Auld , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Masami Hiramatsu , Jakub Kicinski , Pawan Gupta , Simon Horman , Anshuman Khandual , Florian Westphal , netdev@vger.kernel.org, Kees Cook , Arnd Bergmann , "Paul E . McKenney" , Feng Tang , "Jason A . Donenfeld" References: <20251012115035.2169-1-lirongqing@baidu.com> <588c1935-835f-4cab-9679-f31c1e903a9a@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/10/14 17:45, Petr Mladek wrote: > On Tue 2025-10-14 13:23:58, Lance Yang wrote: >> Thanks for the patch! >> >> I noticed the implementation panics only when N tasks are detected >> within a single scan, because total_hung_task is reset for each >> check_hung_uninterruptible_tasks() run. > > Great catch! > > Does it make sense? > Is is the intended behavior, please? > >> So some suggestions to align the documentation with the code's >> behavior below :) > >> On 2025/10/12 19:50, lirongqing wrote: >>> From: Li RongQing >>> >>> Currently, when 'hung_task_panic' is enabled, the kernel panics >>> immediately upon detecting the first hung task. However, some hung >>> tasks are transient and the system can recover, while others are >>> persistent and may accumulate progressively. > > My understanding is that this patch wanted to do: > > + report even temporary stalls > + panic only when the stall was much longer and likely persistent > > Which might make some sense. But the code does something else. Cool. Sounds good to me! > >>> --- a/kernel/hung_task.c >>> +++ b/kernel/hung_task.c >>> @@ -229,9 +232,11 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) >>> */ >>> sysctl_hung_task_detect_count++; >>> + total_hung_task = sysctl_hung_task_detect_count - prev_detect_count; >>> trace_sched_process_hang(t); >>> - if (sysctl_hung_task_panic) { >>> + if (sysctl_hung_task_panic && >>> + (total_hung_task >= sysctl_hung_task_panic)) { >>> console_verbose(); >>> hung_task_show_lock = true; >>> hung_task_call_panic = true; > > I would expect that this patch added another counter, similar to > sysctl_hung_task_detect_count. It would be incremented only > once per check when a hung task was detected. And it would > be cleared (reset) when no hung task was found. Much cleaner. We could add an internal counter for that, yeah. No need to expose it to userspace ;) Petr's suggestion seems to align better with the goal of panicking on persistent hangs, IMHO. Panic after N consecutive checks with hung tasks. @RongQing does that work for you?