| Message ID | 20190528103313.1343-4-jgross@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen: add core scheduling support | expand |
On Tue, 2019-05-28 at 12:32 +0200, Juergen Gross wrote: > Instead of setting the scheduler percpu lock address in each of the > switch_sched instances of the different schedulers do that in > schedule_cpu_switch() which is the single caller of that function. > For that purpose let sched_switch_sched() just return the new lock > address. > This looks good to me. The only actual functional/behavioral difference I've been able to spot is the fact that, in Credit2, we currently switch the lock pointer while still holding the write lock on the global scheduler. After this change, we don't any longer. That being said, I've tried to think about how this could be a problem, but failed at imagining such a scenario, so: > Signed-off-by: Juergen Gross <jgross@suse.com> > Reviewed-by: Dario Faggioli <dfaggioli@suse.com> I'm wondering whether it make sense for the above to be quickly mentioned in the changelog, but am leaning toward "not really necessary". In particular, I don't think it's worth to respin the patch just for that... So, either just something that can be added while committing, or forget it. Regards
>>> On 11.06.19 at 18:55, <dfaggioli@suse.com> wrote: > On Tue, 2019-05-28 at 12:32 +0200, Juergen Gross wrote: >> Instead of setting the scheduler percpu lock address in each of the >> switch_sched instances of the different schedulers do that in >> schedule_cpu_switch() which is the single caller of that function. >> For that purpose let sched_switch_sched() just return the new lock >> address. >> > This looks good to me. The only actual functional/behavioral difference > I've been able to spot is the fact that, in Credit2, we currently > switch the lock pointer while still holding the write lock on the > global scheduler. After this change, we don't any longer. > > That being said, I've tried to think about how this could be a problem, > but failed at imagining such a scenario, so: > >> Signed-off-by: Juergen Gross <jgross@suse.com> >> > Reviewed-by: Dario Faggioli <dfaggioli@suse.com> > > I'm wondering whether it make sense for the above to be quickly > mentioned in the changelog, but am leaning toward "not really > necessary". In particular, I don't think it's worth to respin the patch > just for that... So, either just something that can be added while > committing, or forget it. I'd be happy to add something while committing, but one of you would need to propose the wording of this "something". Jan
On 28/05/2019 11:32, Juergen Gross wrote: > @@ -1870,8 +1871,19 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) > old_lock = pcpu_schedule_lock_irq(cpu); > > vpriv_old = idle->sched_priv; > - ppriv_old = per_cpu(schedule_data, cpu).sched_priv; > - sched_switch_sched(new_ops, cpu, ppriv, vpriv); > + ppriv_old = sd->sched_priv; > + new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv); > + > + per_cpu(scheduler, cpu) = new_ops; > + sd->sched_priv = ppriv; > + > + /* > + * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, > + * if it is free (and it can be) we want that anyone that manages > + * taking it, finds all the initializations we've done above in place. > + */ > + smp_mb(); I realise you're just moving existing code, but this barrier sticks out like a sore thumb. A full memory barrier is a massive overhead for what should be smp_wmb(). The matching barrier is actually hidden in the implicit semantics of managing to lock sd->schedule_lock (which is trial an error anyway), but the only thing that matters here is that all other written data is in place first. Beyond that, local causality will cause all reads to be in order (not that the are important) due to logic dependencies. Any that miss out on this are a optimisation-waiting-to-happen as the compiler could elide them fully. ~Andrew > + sd->schedule_lock = new_lock; > > /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */ > spin_unlock_irq(old_lock);
On 12.06.19 09:40, Jan Beulich wrote: >>>> On 11.06.19 at 18:55, <dfaggioli@suse.com> wrote: >> On Tue, 2019-05-28 at 12:32 +0200, Juergen Gross wrote: >>> Instead of setting the scheduler percpu lock address in each of the >>> switch_sched instances of the different schedulers do that in >>> schedule_cpu_switch() which is the single caller of that function. >>> For that purpose let sched_switch_sched() just return the new lock >>> address. >>> >> This looks good to me. The only actual functional/behavioral difference >> I've been able to spot is the fact that, in Credit2, we currently >> switch the lock pointer while still holding the write lock on the >> global scheduler. After this change, we don't any longer. >> >> That being said, I've tried to think about how this could be a problem, >> but failed at imagining such a scenario, so: >> >>> Signed-off-by: Juergen Gross <jgross@suse.com> >>> >> Reviewed-by: Dario Faggioli <dfaggioli@suse.com> >> >> I'm wondering whether it make sense for the above to be quickly >> mentioned in the changelog, but am leaning toward "not really >> necessary". In particular, I don't think it's worth to respin the patch >> just for that... So, either just something that can be added while >> committing, or forget it. > > I'd be happy to add something while committing, but one of you > would need to propose the wording of this "something". What about: It should be noted that in credit2 the lock used to be set while still holding the global scheduler write lock, which will no longer be true with the new scheme applied. This is actually no problem as the write lock is meant to guard the call of init_pdata() which still is true. Juergen
On 12.06.19 10:05, Andrew Cooper wrote: > On 28/05/2019 11:32, Juergen Gross wrote: >> @@ -1870,8 +1871,19 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) >> old_lock = pcpu_schedule_lock_irq(cpu); >> >> vpriv_old = idle->sched_priv; >> - ppriv_old = per_cpu(schedule_data, cpu).sched_priv; >> - sched_switch_sched(new_ops, cpu, ppriv, vpriv); >> + ppriv_old = sd->sched_priv; >> + new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv); >> + >> + per_cpu(scheduler, cpu) = new_ops; >> + sd->sched_priv = ppriv; >> + >> + /* >> + * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, >> + * if it is free (and it can be) we want that anyone that manages >> + * taking it, finds all the initializations we've done above in place. >> + */ >> + smp_mb(); > > I realise you're just moving existing code, but this barrier sticks out > like a sore thumb. > > A full memory barrier is a massive overhead for what should be > smp_wmb(). The matching barrier is actually hidden in the implicit > semantics of managing to lock sd->schedule_lock (which is trial an error > anyway), but the only thing that matters here is that all other written > data is in place first. > > Beyond that, local causality will cause all reads to be in order (not > that the are important) due to logic dependencies. Any that miss out on > this are a optimisation-waiting-to-happen as the compiler could elide > them fully. Not that it would really matter for performance (switching cpus between cpupools is a _very_ rare operation), I'm fine transforming the barrier into smp_wmb(). Juergen
>>> On 12.06.19 at 10:19, <jgross@suse.com> wrote: > On 12.06.19 10:05, Andrew Cooper wrote: >> On 28/05/2019 11:32, Juergen Gross wrote: >>> @@ -1870,8 +1871,19 @@ int schedule_cpu_switch(unsigned int cpu, struct > cpupool *c) >>> old_lock = pcpu_schedule_lock_irq(cpu); >>> >>> vpriv_old = idle->sched_priv; >>> - ppriv_old = per_cpu(schedule_data, cpu).sched_priv; >>> - sched_switch_sched(new_ops, cpu, ppriv, vpriv); >>> + ppriv_old = sd->sched_priv; >>> + new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv); >>> + >>> + per_cpu(scheduler, cpu) = new_ops; >>> + sd->sched_priv = ppriv; >>> + >>> + /* >>> + * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, >>> + * if it is free (and it can be) we want that anyone that manages >>> + * taking it, finds all the initializations we've done above in place. >>> + */ >>> + smp_mb(); >> >> I realise you're just moving existing code, but this barrier sticks out >> like a sore thumb. >> >> A full memory barrier is a massive overhead for what should be >> smp_wmb(). The matching barrier is actually hidden in the implicit >> semantics of managing to lock sd->schedule_lock (which is trial an error >> anyway), but the only thing that matters here is that all other written >> data is in place first. >> >> Beyond that, local causality will cause all reads to be in order (not >> that the are important) due to logic dependencies. Any that miss out on >> this are a optimisation-waiting-to-happen as the compiler could elide >> them fully. > > Not that it would really matter for performance (switching cpus between > cpupools is a _very_ rare operation), I'm fine transforming the barrier > into smp_wmb(). This again is a change easy enough to make while committing. I'm recording the above in case I end up being the committer. Jan
On Wed, 2019-06-12 at 10:06 +0200, Juergen Gross wrote: > On 12.06.19 09:40, Jan Beulich wrote: > > > > > On 11.06.19 at 18:55, <dfaggioli@suse.com> wrote: > > > On Tue, 2019-05-28 at 12:32 +0200, Juergen Gross wrote: > > > > Signed-off-by: Juergen Gross <jgross@suse.com> > > > > > > > Reviewed-by: Dario Faggioli <dfaggioli@suse.com> > > > > > > I'm wondering whether it make sense for the above to be quickly > > > mentioned in the changelog, but am leaning toward "not really > > > necessary". In particular, I don't think it's worth to respin the > > > patch > > > just for that... So, either just something that can be added > > > while > > > committing, or forget it. > > > > I'd be happy to add something while committing, but one of you > > would need to propose the wording of this "something". > > What about: > > It should be noted that in credit2 the lock used to be set while > still > holding the global scheduler write lock, which will no longer be true > with the new scheme applied. This is actually no problem as the write > lock is meant to guard the call of init_pdata() which still is true. > I'm ok with this. Thanks (to both) and Regards
On Wed, 2019-06-12 at 10:32 +0100, Jan Beulich wrote: > > > > On 12.06.19 at 10:19, <jgross@suse.com> wrote: > > On 12.06.19 10:05, Andrew Cooper wrote: > > > On 28/05/2019 11:32, Juergen Gross wrote: > > > > > > > > + per_cpu(scheduler, cpu) = new_ops; > > > > + sd->sched_priv = ppriv; > > > > + > > > > + /* > > > > + * (Re?)route the lock to the per pCPU lock as /last/ > > > > thing. In fact, > > > > + * if it is free (and it can be) we want that anyone that > > > > manages > > > > + * taking it, finds all the initializations we've done > > > > above in place. > > > > + */ > > > > + smp_mb(); > > > > > > A full memory barrier is a massive overhead for what should be > > > smp_wmb(). The matching barrier is actually hidden in the > > > implicit > > > semantics of managing to lock sd->schedule_lock (which is trial > > > an error > > > anyway), but the only thing that matters here is that all other > > > written > > > data is in place first. > > > > > Not that it would really matter for performance (switching cpus > > between > > cpupools is a _very_ rare operation), I'm fine transforming the > > barrier > > into smp_wmb(). > > This again is a change easy enough to make while committing. I'm > recording the above in case I end up being the committer. > I'm fine (i.e., my Rev-by: remains valid) with this being turned into a wmb(), and it being done upon commit (thanks Jan for the offer to do that!). If we do it, however, I think the comment needs to be adjusted too, and the commit message needs to briefly mention this new change we're doing. Maybe, for the comment, add something like: "The smp_wmb() corresponds to the barrier implicit in successfully taking the lock." And, for the changelog, add: "While there, turn the full barrier, which was overkill, into an smp_wmb(), matching with the one implicit in managing to take the lock." Or something similar (and again, R-b: still stands with such changes). Regards
>>> On 12.06.19 at 11:56, <dfaggioli@suse.com> wrote: > On Wed, 2019-06-12 at 10:32 +0100, Jan Beulich wrote: >> > > > On 12.06.19 at 10:19, <jgross@suse.com> wrote: >> > On 12.06.19 10:05, Andrew Cooper wrote: >> > > On 28/05/2019 11:32, Juergen Gross wrote: >> > > > >> > > > + per_cpu(scheduler, cpu) = new_ops; >> > > > + sd->sched_priv = ppriv; >> > > > + >> > > > + /* >> > > > + * (Re?)route the lock to the per pCPU lock as /last/ >> > > > thing. In fact, >> > > > + * if it is free (and it can be) we want that anyone that >> > > > manages >> > > > + * taking it, finds all the initializations we've done >> > > > above in place. >> > > > + */ >> > > > + smp_mb(); >> > > >> > > A full memory barrier is a massive overhead for what should be >> > > smp_wmb(). The matching barrier is actually hidden in the >> > > implicit >> > > semantics of managing to lock sd->schedule_lock (which is trial >> > > an error >> > > anyway), but the only thing that matters here is that all other >> > > written >> > > data is in place first. >> > > >> > Not that it would really matter for performance (switching cpus >> > between >> > cpupools is a _very_ rare operation), I'm fine transforming the >> > barrier >> > into smp_wmb(). >> >> This again is a change easy enough to make while committing. I'm >> recording the above in case I end up being the committer. >> > I'm fine (i.e., my Rev-by: remains valid) with this being turned into a > wmb(), and it being done upon commit (thanks Jan for the offer to do > that!). > > If we do it, however, I think the comment needs to be adjusted too, and > the commit message needs to briefly mention this new change we're > doing. > > Maybe, for the comment, add something like: > > "The smp_wmb() corresponds to the barrier implicit in successfully > taking the lock." I'm not entirely happy with this one: Taking a lock is an implicit full barrier, so cannot alone be used to reason why a write barrier is sufficient here. > And, for the changelog, add: > > "While there, turn the full barrier, which was overkill, into an > smp_wmb(), matching with the one implicit in managing to take the > lock." This one reads fine to me. Jan
On 12/06/2019 11:14, Jan Beulich wrote: >>>> On 12.06.19 at 11:56, <dfaggioli@suse.com> wrote: >> On Wed, 2019-06-12 at 10:32 +0100, Jan Beulich wrote: >>>>>> On 12.06.19 at 10:19, <jgross@suse.com> wrote: >>>> On 12.06.19 10:05, Andrew Cooper wrote: >>>>> On 28/05/2019 11:32, Juergen Gross wrote: >>>>>> + per_cpu(scheduler, cpu) = new_ops; >>>>>> + sd->sched_priv = ppriv; >>>>>> + >>>>>> + /* >>>>>> + * (Re?)route the lock to the per pCPU lock as /last/ >>>>>> thing. In fact, >>>>>> + * if it is free (and it can be) we want that anyone that >>>>>> manages >>>>>> + * taking it, finds all the initializations we've done >>>>>> above in place. >>>>>> + */ >>>>>> + smp_mb(); >>>>> A full memory barrier is a massive overhead for what should be >>>>> smp_wmb(). The matching barrier is actually hidden in the >>>>> implicit >>>>> semantics of managing to lock sd->schedule_lock (which is trial >>>>> an error >>>>> anyway), but the only thing that matters here is that all other >>>>> written >>>>> data is in place first. >>>>> >>>> Not that it would really matter for performance (switching cpus >>>> between >>>> cpupools is a _very_ rare operation), I'm fine transforming the >>>> barrier >>>> into smp_wmb(). >>> This again is a change easy enough to make while committing. I'm >>> recording the above in case I end up being the committer. >>> >> I'm fine (i.e., my Rev-by: remains valid) with this being turned into a >> wmb(), and it being done upon commit (thanks Jan for the offer to do >> that!). >> >> If we do it, however, I think the comment needs to be adjusted too, and >> the commit message needs to briefly mention this new change we're >> doing. >> >> Maybe, for the comment, add something like: >> >> "The smp_wmb() corresponds to the barrier implicit in successfully >> taking the lock." > I'm not entirely happy with this one: Taking a lock is an implicit full > barrier, so cannot alone be used to reason why a write barrier is > sufficient here. It is a consequence of our extra magic scheduler locks which protect the pointer used to locate them, and the ensuing double-step in ??? (seriously - I can't figure out the function names created by the sched_lock() monstrosity) which take the lock, re-read the lock pointer and drop on a mismatch. I've gone with: + /* + * The data above is protected under new_lock, which may be unlocked. + * Another CPU can take new_lock as soon as sd->schedule_lock is visible, + * and must observe all prior initialisation. + */ + smp_wmb(); ~Andrew
On Wed, 2019-06-12 at 12:27 +0100, Andrew Cooper wrote: > It is a consequence of our extra magic scheduler locks which protect > the > pointer used to locate them, and the ensuing double-step in ??? > (seriously - I can't figure out the function names created by the > sched_lock() monstrosity) which take the lock, re-read the lock > pointer > and drop on a mismatch. > Just FTR, they're: vcpu_schedule_lock() vcpu_schedule_lock_irq() vcpu_schedule_lock_irqsave() and: pcpu_schedule_lock() pcpu_schedule_lock_irq() pcpu_schedule_lock_irqsave() and the corresponding *_schedule_unlock_*() ones, of course. ;-P Regards
diff --git a/xen/common/sched_arinc653.c b/xen/common/sched_arinc653.c index a4c6d00b81..72b988ea5f 100644 --- a/xen/common/sched_arinc653.c +++ b/xen/common/sched_arinc653.c @@ -630,7 +630,7 @@ a653sched_pick_cpu(const struct scheduler *ops, struct vcpu *vc) * @param pdata scheduler specific PCPU data (we don't have any) * @param vdata scheduler specific VCPU data of the idle vcpu */ -static void +static spinlock_t * a653_switch_sched(struct scheduler *new_ops, unsigned int cpu, void *pdata, void *vdata) { @@ -641,17 +641,7 @@ a653_switch_sched(struct scheduler *new_ops, unsigned int cpu, idle_vcpu[cpu]->sched_priv = vdata; - per_cpu(scheduler, cpu) = new_ops; - per_cpu(schedule_data, cpu).sched_priv = NULL; /* no pdata */ - - /* - * (Re?)route the lock to its default location. We actually do not use - * it, but if we leave it pointing to where it does now (i.e., the - * runqueue lock for this PCPU in the default scheduler), we'd be - * causing unnecessary contention on that lock (in cases where it is - * shared among multiple PCPUs, like in Credit2 and RTDS). - */ - sd->schedule_lock = &sd->_lock; + return &sd->_lock; } /** diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c index 7b7facbace..621c408ed0 100644 --- a/xen/common/sched_credit.c +++ b/xen/common/sched_credit.c @@ -631,7 +631,7 @@ csched_init_pdata(const struct scheduler *ops, void *pdata, int cpu) } /* Change the scheduler of cpu to us (Credit). */ -static void +static spinlock_t * csched_switch_sched(struct scheduler *new_ops, unsigned int cpu, void *pdata, void *vdata) { @@ -653,16 +653,7 @@ csched_switch_sched(struct scheduler *new_ops, unsigned int cpu, init_pdata(prv, pdata, cpu); spin_unlock(&prv->lock); - per_cpu(scheduler, cpu) = new_ops; - per_cpu(schedule_data, cpu).sched_priv = pdata; - - /* - * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, - * if it is free (and it can be) we want that anyone that manages - * taking it, finds all the initializations we've done above in place. - */ - smp_mb(); - sd->schedule_lock = &sd->_lock; + return &sd->_lock; } #ifndef NDEBUG diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c index 9c1c3b4e08..8e4381d8a7 100644 --- a/xen/common/sched_credit2.c +++ b/xen/common/sched_credit2.c @@ -3855,7 +3855,7 @@ csched2_init_pdata(const struct scheduler *ops, void *pdata, int cpu) } /* Change the scheduler of cpu to us (Credit2). */ -static void +static spinlock_t * csched2_switch_sched(struct scheduler *new_ops, unsigned int cpu, void *pdata, void *vdata) { @@ -3888,18 +3888,9 @@ csched2_switch_sched(struct scheduler *new_ops, unsigned int cpu, */ ASSERT(per_cpu(schedule_data, cpu).schedule_lock != &prv->rqd[rqi].lock); - per_cpu(scheduler, cpu) = new_ops; - per_cpu(schedule_data, cpu).sched_priv = pdata; - - /* - * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, - * if it is free (and it can be) we want that anyone that manages - * taking it, find all the initializations we've done above in place. - */ - smp_mb(); - per_cpu(schedule_data, cpu).schedule_lock = &prv->rqd[rqi].lock; - write_unlock(&prv->lock); + + return &prv->rqd[rqi].lock; } static void diff --git a/xen/common/sched_null.c b/xen/common/sched_null.c index a59dbb2692..10427b37ab 100644 --- a/xen/common/sched_null.c +++ b/xen/common/sched_null.c @@ -381,8 +381,9 @@ static void vcpu_deassign(struct null_private *prv, struct vcpu *v, } /* Change the scheduler of cpu to us (null). */ -static void null_switch_sched(struct scheduler *new_ops, unsigned int cpu, - void *pdata, void *vdata) +static spinlock_t *null_switch_sched(struct scheduler *new_ops, + unsigned int cpu, + void *pdata, void *vdata) { struct schedule_data *sd = &per_cpu(schedule_data, cpu); struct null_private *prv = null_priv(new_ops); @@ -401,16 +402,7 @@ static void null_switch_sched(struct scheduler *new_ops, unsigned int cpu, init_pdata(prv, cpu); - per_cpu(scheduler, cpu) = new_ops; - per_cpu(schedule_data, cpu).sched_priv = pdata; - - /* - * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, - * if it is free (and it can be) we want that anyone that manages - * taking it, finds all the initializations we've done above in place. - */ - smp_mb(); - sd->schedule_lock = &sd->_lock; + return &sd->_lock; } static void null_vcpu_insert(const struct scheduler *ops, struct vcpu *v) diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c index f1b81f0373..0acfc3d702 100644 --- a/xen/common/sched_rt.c +++ b/xen/common/sched_rt.c @@ -729,7 +729,7 @@ rt_init_pdata(const struct scheduler *ops, void *pdata, int cpu) } /* Change the scheduler of cpu to us (RTDS). */ -static void +static spinlock_t * rt_switch_sched(struct scheduler *new_ops, unsigned int cpu, void *pdata, void *vdata) { @@ -761,16 +761,8 @@ rt_switch_sched(struct scheduler *new_ops, unsigned int cpu, } idle_vcpu[cpu]->sched_priv = vdata; - per_cpu(scheduler, cpu) = new_ops; - per_cpu(schedule_data, cpu).sched_priv = NULL; /* no pdata */ - /* - * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, - * if it is free (and it can be) we want that anyone that manages - * taking it, find all the initializations we've done above in place. - */ - smp_mb(); - per_cpu(schedule_data, cpu).schedule_lock = &prv->lock; + return &prv->lock; } static void diff --git a/xen/common/schedule.c b/xen/common/schedule.c index 4da970c543..6dc96b3cd4 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -1812,7 +1812,8 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) struct scheduler *old_ops = per_cpu(scheduler, cpu); struct scheduler *new_ops = (c == NULL) ? &ops : c->sched; struct cpupool *old_pool = per_cpu(cpupool, cpu); - spinlock_t * old_lock; + struct schedule_data *sd = &per_cpu(schedule_data, cpu); + spinlock_t *old_lock, *new_lock; /* * pCPUs only move from a valid cpupool to free (i.e., out of any pool), @@ -1870,8 +1871,19 @@ int schedule_cpu_switch(unsigned int cpu, struct cpupool *c) old_lock = pcpu_schedule_lock_irq(cpu); vpriv_old = idle->sched_priv; - ppriv_old = per_cpu(schedule_data, cpu).sched_priv; - sched_switch_sched(new_ops, cpu, ppriv, vpriv); + ppriv_old = sd->sched_priv; + new_lock = sched_switch_sched(new_ops, cpu, ppriv, vpriv); + + per_cpu(scheduler, cpu) = new_ops; + sd->sched_priv = ppriv; + + /* + * (Re?)route the lock to the per pCPU lock as /last/ thing. In fact, + * if it is free (and it can be) we want that anyone that manages + * taking it, finds all the initializations we've done above in place. + */ + smp_mb(); + sd->schedule_lock = new_lock; /* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */ spin_unlock_irq(old_lock); diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h index b3c3e189d9..b8e2b2e49e 100644 --- a/xen/include/xen/sched-if.h +++ b/xen/include/xen/sched-if.h @@ -153,7 +153,7 @@ struct scheduler { /* Idempotent. */ void (*free_domdata) (const struct scheduler *, void *); - void (*switch_sched) (struct scheduler *, unsigned int, + spinlock_t * (*switch_sched) (struct scheduler *, unsigned int, void *, void *); /* Activate / deactivate vcpus in a cpu pool */ @@ -195,10 +195,11 @@ static inline void sched_deinit(struct scheduler *s) s->deinit(s); } -static inline void sched_switch_sched(struct scheduler *s, unsigned int cpu, - void *pdata, void *vdata) +static inline spinlock_t *sched_switch_sched(struct scheduler *s, + unsigned int cpu, + void *pdata, void *vdata) { - s->switch_sched(s, cpu, pdata, vdata); + return s->switch_sched(s, cpu, pdata, vdata); } static inline void sched_dump_settings(const struct scheduler *s)
Instead of setting the scheduler percpu lock address in each of the switch_sched instances of the different schedulers do that in schedule_cpu_switch() which is the single caller of that function. For that purpose let sched_switch_sched() just return the new lock address. This allows to set the new struct scheduler and struct schedule_data values in the percpu area in schedule_cpu_switch() instead of the schedulers, too. Signed-off-by: Juergen Gross <jgross@suse.com> --- xen/common/sched_arinc653.c | 14 ++------------ xen/common/sched_credit.c | 13 ++----------- xen/common/sched_credit2.c | 15 +++------------ xen/common/sched_null.c | 16 ++++------------ xen/common/sched_rt.c | 12 ++---------- xen/common/schedule.c | 18 +++++++++++++++--- xen/include/xen/sched-if.h | 9 +++++---- 7 files changed, 33 insertions(+), 64 deletions(-)