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Message-ID: <20160120100839.GL8573@e106622-lin>
Date: Wed, 20 Jan 2016 10:08:39 +0000
From: Juri Lelli <juri.lelli@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...nel.org, linux-kernel@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
Steven Rostedt <rostedt@...dmis.org>,
Juri Lelli <juri.lelli@...il.com>,
Andrea Parri <parri.andrea@...il.com>
Subject: Re: [PATCH] sched: Fix PI handling vs sched_setscheduler()
Hi,
On 19/01/16 12:18, Peter Zijlstra wrote:
[...]
> @@ -4097,15 +4099,14 @@ static int __sched_setscheduler(struct t
> if (running)
> p->sched_class->set_curr_task(rq);
> if (queued) {
> - int enqueue_flags = ENQUEUE_RESTORE;
> /*
> * We enqueue to tail when the priority of a task is
> * increased (user space view).
> */
> - if (oldprio <= p->prio)
> - enqueue_flags |= ENQUEUE_HEAD;
> + if (oldprio < p->prio)
> + queue_flags |= ENQUEUE_HEAD;
Was this condition broken before or it needs to be changed now with this
patch?
[...]
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1130,18 +1130,35 @@ static inline void finish_lock_switch(st
> extern const int sched_prio_to_weight[40];
> extern const u32 sched_prio_to_wmult[40];
>
> +/*
> + * {de,en}queue flags:
> + *
> + * SAVE/RESTORE - an otherwise spurious dequeue/enqueue, done to ensure tasks
> + * are in a known state which allows modification. Such pairs
> + * should preserve as much state as possible.
> + *
> + * MOVE - paired with SAVE/RESTORE, explicitly does not preserve the location
> + * in the runqueue.
> + *
> + * ENQUEUE_HEAD - place at front of runqueue (tail if not specificed)
> + *
> + */
Do we want to document all the flags while we are at it? :)
Best,
- Juri
> +
> +#define DEQUEUE_SLEEP 0x01
> +#define DEQUEUE_SAVE 0x02 /* matches ENQUEUE_RESTORE */
> +#define DEQUEUE_MOVE 0x04 /* matches ENQUEUE_MOVE */
> +
> #define ENQUEUE_WAKEUP 0x01
> -#define ENQUEUE_HEAD 0x02
> +#define ENQUEUE_RESTORE 0x02
> +#define ENQUEUE_MOVE 0x04
> +
> +#define ENQUEUE_HEAD 0x08
> +#define ENQUEUE_REPLENISH 0x10
> #ifdef CONFIG_SMP
> -#define ENQUEUE_WAKING 0x04 /* sched_class::task_waking was called */
> +#define ENQUEUE_WAKING 0x20 /* sched_class::task_waking was called */
> #else
> #define ENQUEUE_WAKING 0x00
> #endif
> -#define ENQUEUE_REPLENISH 0x08
> -#define ENQUEUE_RESTORE 0x10
> -
> -#define DEQUEUE_SLEEP 0x01
> -#define DEQUEUE_SAVE 0x02
>
> #define RETRY_TASK ((void *)-1UL)
>
>
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