linux-kernel - Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic

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Message-ID: <985463a3-5e33-95d2-b2bb-824707a2f819@linux.ibm.com>
Date:   Tue, 27 Sep 2022 07:35:14 +0200
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     bigeasy@...utronix.de, dietmar.eggemann@....com,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, mgorman@...e.de, mingo@...nel.org,
        oleg@...hat.com, rjw@...ysocki.net, rostedt@...dmis.org,
        tj@...nel.org, vincent.guittot@...aro.org, will@...nel.org,
        Marc Hartmayer <mhartmay@...ux.ibm.com>,
        Amit Shah <amit@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic



Am 26.09.22 um 20:22 schrieb Peter Zijlstra:
> On Mon, Sep 26, 2022 at 08:06:46PM +0200, Peter Zijlstra wrote:
> 
>> Let me go git-grep some to see if there's more similar fail.
> 
> I've ended up with the below...

Tested-by: Christian Borntraeger <borntraeger@...ibm.com>

Kind of scary that nobody else has reported any regression. I guess the freezable variant is just not used widely.
> 
> ---
>   include/linux/wait.h | 2 +-
>   kernel/hung_task.c   | 8 ++++++--
>   kernel/sched/core.c  | 2 +-
>   3 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index 14ad8a0e9fac..7f5a51aae0a7 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -281,7 +281,7 @@ static inline void wake_up_pollfree(struct wait_queue_head *wq_head)
>   
>   #define ___wait_is_interruptible(state)						\
>   	(!__builtin_constant_p(state) ||					\
> -		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
> +	 (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
>   
>   extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
>   
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index f1321c03c32a..4a8a713fd67b 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -191,6 +191,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>   	hung_task_show_lock = false;
>   	rcu_read_lock();
>   	for_each_process_thread(g, t) {
> +		unsigned int state;
> +
>   		if (!max_count--)
>   			goto unlock;
>   		if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
> @@ -198,8 +200,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>   				goto unlock;
>   			last_break = jiffies;
>   		}
> -		/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
> -		if (READ_ONCE(t->__state) == TASK_UNINTERRUPTIBLE)
> +		/* skip the TASK_KILLABLE tasks -- these can be killed */
> +		state == READ_ONCE(t->__state);
> +		if ((state & TASK_UNINTERRUPTIBLE) &&
> +		    !(state & TASK_WAKEKILL))
>   			check_hung_task(t, timeout);
>   	}
>    unlock:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1095917ed048..12ee5b98e2c4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8885,7 +8885,7 @@ state_filter_match(unsigned long state_filter, struct task_struct *p)
>   	 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
>   	 * TASK_KILLABLE).
>   	 */
> -	if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE)
> +	if (state_filter == TASK_UNINTERRUPTIBLE && state & TASK_NOLOAD)
>   		return false;
>   
>   	return true;