Re: [RFC v5 PATCH 1/8] sched: Rename struct rt_bandwidth to sched_bandwidth

Bharata B Rao
2010-01-29T14:08:27Z

On Fri, Jan 29, 2010 at 02:29:49PM +0530, Balbir Singh wrote:
> * Bharata B Rao <bharata@linux.vnet.ibm.com> [2010-01-05 13:28:24]:
>
> > sched: Rename struct rt_bandwidth to sched_bandwidth
> >
> > From: Dhaval Giani <dhaval@linux.vnet.ibm.com>
> >
> > Rename struct rt_bandwidth to sched_bandwidth and rename some of the
> > routines to generic names (s/rt_/sched_) so that they can be used
> > by CFS hard limits code in the subsequent patches.
> >
> > No functionality change by this patch.
> >
> > Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
>
> Looks good, some nit picks below
>
> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>

Thanks Balbir.

>
>
> > ---
> > kernel/sched.c | 127 ++++++++++++++++++++++++++---------------------------
> > kernel/sched_rt.c | 46 ++++++++++---------
> > 2 files changed, 86 insertions(+), 87 deletions(-)
> >
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index c535cc4..21cf0d5 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -139,50 +139,50 @@ struct rt_prio_array {
> > struct list_head queue[MAX_RT_PRIO];
> > };
> >
> > -struct rt_bandwidth {
> > +struct sched_bandwidth {
> > /* nests inside the rq lock: */
> > - raw_spinlock_t rt_runtime_lock;
> > - ktime_t rt_period;
> > - u64 rt_runtime;
> > - struct hrtimer rt_period_timer;
> > + raw_spinlock_t runtime_lock;
> > + ktime_t period;
> > + u64 runtime;
> > + struct hrtimer period_timer;
> > };
> >
> > -static struct rt_bandwidth def_rt_bandwidth;
> > +static struct sched_bandwidth def_rt_bandwidth;
> >
> > -static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
> > +static int do_sched_rt_period_timer(struct sched_bandwidth *sched_b, int overrun);
> >
> > static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
> > {
> > - struct rt_bandwidth *rt_b =
> > - container_of(timer, struct rt_bandwidth, rt_period_timer);
> > + struct sched_bandwidth *sched_b =
> > + container_of(timer, struct sched_bandwidth, period_timer);
> > ktime_t now;
> > int overrun;
> > int idle = 0;
> >
> > for (;;) {
> > now = hrtimer_cb_get_time(timer);
> > - overrun = hrtimer_forward(timer, now, rt_b->rt_period);
> > + overrun = hrtimer_forward(timer, now, sched_b->period);
> >
> > if (!overrun)
> > break;
> >
> > - idle = do_sched_rt_period_timer(rt_b, overrun);
> > + idle = do_sched_rt_period_timer(sched_b, overrun);
> > }
> >
> > return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
> > }
> >
> > -static
> > -void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
> > +static void init_sched_bandwidth(struct sched_bandwidth *sched_b, u64 period,
> > + u64 runtime, enum hrtimer_restart (*period_timer)(struct hrtimer *))
> > {
> > - rt_b->rt_period = ns_to_ktime(period);
> > - rt_b->rt_runtime = runtime;
> > + sched_b->period = ns_to_ktime(period);
> > + sched_b->runtime = runtime;
> >
> > - raw_spin_lock_init(&rt_b->rt_runtime_lock);
> > + raw_spin_lock_init(&sched_b->runtime_lock);
> >
> > - hrtimer_init(&rt_b->rt_period_timer,
> > + hrtimer_init(&sched_b->period_timer,
> > CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > - rt_b->rt_period_timer.function = sched_rt_period_timer;
> > + sched_b->period_timer.function = *period_timer;
>
> Hmm.. may be I forgetting the "C" language, but why do you dereference
> the pointer before assignment? You should be able to directly assign a
> function address to the function pointer. Did you see a warning?

This is a carry over from old patches. I will fix this
in the next iteration.

>
> > }
> >
> > static inline int rt_bandwidth_enabled(void)
> > @@ -190,42 +190,40 @@ static inline int rt_bandwidth_enabled(void)
> > return sysctl_sched_rt_runtime >= 0;
> > }
> >
> > -static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
> > +static void start_sched_bandwidth(struct sched_bandwidth *sched_b)
> > {
> > ktime_t now;
> >
> > - if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
> > + if (!rt_bandwidth_enabled() || sched_b->runtime == RUNTIME_INF)
> > return;
> >
> > - if (hrtimer_active(&rt_b->rt_period_timer))
> > + if (hrtimer_active(&sched_b->period_timer))
> > return;
> >
> > - raw_spin_lock(&rt_b->rt_runtime_lock);
> > + raw_spin_lock(&sched_b->runtime_lock);
>
> I don't quite understand why this is a raw_spin_lock

- When upgrading from v4 (2.6.32-rc6) to v5 (2.6.33-rc2), I needed
to change most of the spin_locks in hard limits code in sched.c
since they had become raw_spin_lock_t.
- If your question is why couldn't we use spin_lock_t (sleepable types),
this routine is called from RT and CFS with rq->lock (raw type) held.
So I guess it is not possible to use sleepable version here.

Thanks for your reivew. Would appreciate review of other patches also :)

Regards,
Bharata.