| Message ID | 20230612093537.977924652@infradead.org (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | Scope-based Resource Management | expand |
On Mon, Jun 12, 2023 at 11:07:21AM +0200, Peter Zijlstra wrote: > Use guards to reduce gotos and simplify control flow. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/sched/core.c | 20 ++++++-------------- > kernel/sched/sched.h | 15 +++++++++++++++ > 2 files changed, 21 insertions(+), 14 deletions(-) > > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct > void wake_up_if_idle(int cpu) > { > struct rq *rq = cpu_rq(cpu); > - struct rq_flags rf; > > - rcu_read_lock(); > - > - if (!is_idle_task(rcu_dereference(rq->curr))) > - goto out; > - > - rq_lock_irqsave(rq, &rf); > - if (is_idle_task(rq->curr)) > - resched_curr(rq); > - /* Else CPU is not idle, do nothing here: */ > - rq_unlock_irqrestore(rq, &rf); > - > -out: > - rcu_read_unlock(); > + guard(rcu)(); > + if (is_idle_task(rcu_dereference(rq->curr))) { > + guard(rq_lock)(rq); We assume that irq must be disabled when this function called? Otherwise, I don't understand why this is not guard(rq_lock_irqsave)(rq); ? Regards, Boqun > + if (is_idle_task(rq->curr)) > + resched_curr(rq); > + } > } > > bool cpus_share_cache(int this_cpu, int that_cpu) > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1678,6 +1678,21 @@ rq_unlock(struct rq *rq, struct rq_flags > raw_spin_rq_unlock(rq); > } > > +DEFINE_LOCK_GUARD_1(rq_lock, struct rq, > + rq_lock(_T->lock, &_T->rf), > + rq_unlock(_T->lock, &_T->rf), > + struct rq_flags rf) > + > +DEFINE_LOCK_GUARD_1(rq_lock_irq, struct rq, > + rq_lock_irq(_T->lock, &_T->rf), > + rq_unlock_irq(_T->lock, &_T->rf), > + struct rq_flags rf) > + > +DEFINE_LOCK_GUARD_1(rq_lock_irqsave, struct rq, > + rq_lock_irqsave(_T->lock, &_T->rf), > + rq_unlock_irqrestore(_T->lock, &_T->rf), > + struct rq_flags rf) > + > static inline struct rq * > this_rq_lock_irq(struct rq_flags *rf) > __acquires(rq->lock) > >
On Mon, Jun 12, 2023 at 11:02:28AM -0700, Boqun Feng wrote: > On Mon, Jun 12, 2023 at 11:07:21AM +0200, Peter Zijlstra wrote: > > Use guards to reduce gotos and simplify control flow. > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > kernel/sched/core.c | 20 ++++++-------------- > > kernel/sched/sched.h | 15 +++++++++++++++ > > 2 files changed, 21 insertions(+), 14 deletions(-) > > > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct > > void wake_up_if_idle(int cpu) > > { > > struct rq *rq = cpu_rq(cpu); > > - struct rq_flags rf; > > > > - rcu_read_lock(); > > - > > - if (!is_idle_task(rcu_dereference(rq->curr))) > > - goto out; > > - > > - rq_lock_irqsave(rq, &rf); > > - if (is_idle_task(rq->curr)) > > - resched_curr(rq); > > - /* Else CPU is not idle, do nothing here: */ > > - rq_unlock_irqrestore(rq, &rf); > > - > > -out: > > - rcu_read_unlock(); > > + guard(rcu)(); > > + if (is_idle_task(rcu_dereference(rq->curr))) { > > + guard(rq_lock)(rq); > > We assume that irq must be disabled when this function called? > Otherwise, I don't understand why this is not > > guard(rq_lock_irqsave)(rq); > You're quite right, I messed that up.
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3872,21 +3872,13 @@ static void __ttwu_queue_wakelist(struct void wake_up_if_idle(int cpu) { struct rq *rq = cpu_rq(cpu); - struct rq_flags rf; - rcu_read_lock(); - - if (!is_idle_task(rcu_dereference(rq->curr))) - goto out; - - rq_lock_irqsave(rq, &rf); - if (is_idle_task(rq->curr)) - resched_curr(rq); - /* Else CPU is not idle, do nothing here: */ - rq_unlock_irqrestore(rq, &rf); - -out: - rcu_read_unlock(); + guard(rcu)(); + if (is_idle_task(rcu_dereference(rq->curr))) { + guard(rq_lock)(rq); + if (is_idle_task(rq->curr)) + resched_curr(rq); + } } bool cpus_share_cache(int this_cpu, int that_cpu) --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1678,6 +1678,21 @@ rq_unlock(struct rq *rq, struct rq_flags raw_spin_rq_unlock(rq); } +DEFINE_LOCK_GUARD_1(rq_lock, struct rq, + rq_lock(_T->lock, &_T->rf), + rq_unlock(_T->lock, &_T->rf), + struct rq_flags rf) + +DEFINE_LOCK_GUARD_1(rq_lock_irq, struct rq, + rq_lock_irq(_T->lock, &_T->rf), + rq_unlock_irq(_T->lock, &_T->rf), + struct rq_flags rf) + +DEFINE_LOCK_GUARD_1(rq_lock_irqsave, struct rq, + rq_lock_irqsave(_T->lock, &_T->rf), + rq_unlock_irqrestore(_T->lock, &_T->rf), + struct rq_flags rf) + static inline struct rq * this_rq_lock_irq(struct rq_flags *rf) __acquires(rq->lock)
Use guards to reduce gotos and simplify control flow. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/sched/core.c | 20 ++++++-------------- kernel/sched/sched.h | 15 +++++++++++++++ 2 files changed, 21 insertions(+), 14 deletions(-)