Re: [RFC PATCH 5/9] sched: move task rq locking functions to sched.h

Masami Hiramatsu
2015-02-10T10:48:26Z

(2015/02/10 2:31), Josh Poimboeuf wrote:
> Move task_rq_lock/unlock() to sched.h so they can be used elsewhere.
> The livepatch code needs to lock each task's rq in order to safely
> examine its stack and switch it to a new patch universe.

Hmm, why don't you just expose (extern in sched.h) those?

Thank you,

>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> kernel/sched/core.c | 32 --------------------------------
> kernel/sched/sched.h | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 33 insertions(+), 32 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b5797b7..78d91e6 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -326,44 +326,12 @@ static inline struct rq *__task_rq_lock(struct task_struct *p)
> }
> }
>
> -/*
> - * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
> - */
> -static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
> - __acquires(p->pi_lock)
> - __acquires(rq->lock)
> -{
> - struct rq *rq;
> -
> - for (;;) {
> - raw_spin_lock_irqsave(&p->pi_lock, *flags);
> - rq = task_rq(p);
> - raw_spin_lock(&rq->lock);
> - if (likely(rq == task_rq(p) && !task_on_rq_migrating(p)))
> - return rq;
> - raw_spin_unlock(&rq->lock);
> - raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
> -
> - while (unlikely(task_on_rq_migrating(p)))
> - cpu_relax();
> - }
> -}
> -
> static void __task_rq_unlock(struct rq *rq)
> __releases(rq->lock)
> {
> raw_spin_unlock(&rq->lock);
> }
>
> -static inline void
> -task_rq_unlock(struct rq *rq, struct task_struct *p, unsigned long *flags)
> - __releases(rq->lock)
> - __releases(p->pi_lock)
> -{
> - raw_spin_unlock(&rq->lock);
> - raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
> -}
> -
> /*
> * this_rq_lock - lock this runqueue and disable interrupts.
> */
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 9a2a45c..ae514c9 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1542,6 +1542,39 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
>
> #endif
>
> +/*
> + * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
> + */
> +static inline struct rq *task_rq_lock(struct task_struct *p,
> + unsigned long *flags)
> + __acquires(p->pi_lock)
> + __acquires(rq->lock)
> +{
> + struct rq *rq;
> +
> + for (;;) {
> + raw_spin_lock_irqsave(&p->pi_lock, *flags);
> + rq = task_rq(p);
> + raw_spin_lock(&rq->lock);
> + if (likely(rq == task_rq(p) && !task_on_rq_migrating(p)))
> + return rq;
> + raw_spin_unlock(&rq->lock);
> + raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
> +
> + while (unlikely(task_on_rq_migrating(p)))
> + cpu_relax();
> + }
> +}
> +
> +static inline void task_rq_unlock(struct rq *rq, struct task_struct *p,
> + unsigned long *flags)
> + __releases(rq->lock)
> + __releases(p->pi_lock)
> +{
> + raw_spin_unlock(&rq->lock);
> + raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
> +}
> +
> extern struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq);
> extern struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq);
> extern void print_cfs_stats(struct seq_file *m, int cpu);
>

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com