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sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW

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Now that the last architecture to use this has stopped doing so (ARM,
thanks Catalin!) we can remove this complexity from the scheduler
core.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: http://lkml.kernel.org/n/tip-g9p2a1w81xxbrze25v9zpzbf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2012-09-12 11:22:00 +02:00 committed by Ingo Molnar
parent 5ed4f1d96d
commit f3e9478674
6 changed files with 1 additions and 69 deletions
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10
Documentation/scheduler/sched-arch.txt
View file

@ -17,16 +17,6 @@ you must `#define __ARCH_WANT_UNLOCKED_CTXSW` in a header file
Unlocked context switches introduce only a very minor performance
penalty to the core scheduler implementation in the CONFIG_SMP case.
2. Interrupt status
By default, the switch_to arch function is called with interrupts
disabled. Interrupts may be enabled over the call if it is likely to
introduce a significant interrupt latency by adding the line
`#define __ARCH_WANT_INTERRUPTS_ON_CTXSW` in the same place as for
unlocked context switches. This define also implies
`__ARCH_WANT_UNLOCKED_CTXSW`. See arch/arm/include/asm/system.h for an
example.
CPU idle
========
Your cpu_idle routines need to obey the following rules:

5
include/linux/sched.h
View file

@ -678,11 +678,6 @@ struct signal_struct {
* (notably. ptrace) */
};
/* Context switch must be unlocked if interrupts are to be enabled */
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
# define __ARCH_WANT_UNLOCKED_CTXSW
#endif
/*
* Bits in flags field of signal_struct.
*/

4
kernel/fork.c
View file

@ -1280,11 +1280,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
p->irq_events = 0;
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
p->hardirqs_enabled = 1;
#else
p->hardirqs_enabled = 0;
#endif
p->hardirq_enable_ip = 0;
p->hardirq_enable_event = 0;
p->hardirq_disable_ip = _THIS_IP_;

40
kernel/sched/core.c
View file

@ -1361,25 +1361,6 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu)
smp_send_reschedule(cpu);
}
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
static int ttwu_activate_remote(struct task_struct *p, int wake_flags)
{
struct rq *rq;
int ret = 0;
rq = __task_rq_lock(p);
if (p->on_cpu) {
ttwu_activate(rq, p, ENQUEUE_WAKEUP);
ttwu_do_wakeup(rq, p, wake_flags);
ret = 1;
}
__task_rq_unlock(rq);
return ret;
}
#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
bool cpus_share_cache(int this_cpu, int that_cpu)
{
return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
@ -1440,21 +1421,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
* If the owning (remote) cpu is still in the middle of schedule() with
* this task as prev, wait until its done referencing the task.
*/
while (p->on_cpu) {
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
/*
* In case the architecture enables interrupts in
* context_switch(), we cannot busy wait, since that
* would lead to deadlocks when an interrupt hits and
* tries to wake up @prev. So bail and do a complete
* remote wakeup.
*/
if (ttwu_activate_remote(p, wake_flags))
goto stat;
#else
while (p->on_cpu)
cpu_relax();
#endif
}
/*
* Pairs with the smp_wmb() in finish_lock_switch().
*/
@ -1798,13 +1766,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
prev_state = prev->state;
account_switch_vtime(prev);
finish_arch_switch(prev);
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_disable();
#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
perf_event_task_sched_in(prev, current);
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
finish_lock_switch(rq, prev);
finish_arch_post_lock_switch();

5
kernel/sched/rt.c
View file

@ -1632,11 +1632,6 @@ static int push_rt_task(struct rq *rq)
if (!next_task)
return 0;
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
if (unlikely(task_running(rq, next_task)))
return 0;
#endif
retry:
if (unlikely(next_task == rq->curr)) {
WARN_ON(1);

6
kernel/sched/sched.h
View file

@ -737,11 +737,7 @@ static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
*/
next->on_cpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
raw_spin_unlock_irq(&rq->lock);
#else
raw_spin_unlock(&rq->lock);
#endif
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
@ -755,9 +751,7 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
smp_wmb();
prev->on_cpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
#endif
}
#endif /* __ARCH_WANT_UNLOCKED_CTXSW */