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

Christian Borntraeger
2022-09-27T05:35:55Z

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@de.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;