[tip:sched/core] sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
From: tip-bot for Peter Zijlstra
Date: Fri Sep 14 2012 - 02:13:33 EST
Commit-ID: f3e947867478af9a12b9956bcd000ac7613a8a95
Gitweb: http://git.kernel.org/tip/f3e947867478af9a12b9956bcd000ac7613a8a95
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Wed, 12 Sep 2012 11:22:00 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 13 Sep 2012 16:52:04 +0200
sched: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW
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@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Link: http://lkml.kernel.org/n/tip-g9p2a1w81xxbrze25v9zpzbf@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
Documentation/scheduler/sched-arch.txt | 10 --------
include/linux/sched.h | 5 ----
kernel/fork.c | 4 ---
kernel/sched/core.c | 40 +-------------------------------
kernel/sched/rt.c | 5 ----
kernel/sched/sched.h | 6 ----
6 files changed, 1 insertions(+), 69 deletions(-)
diff --git a/Documentation/scheduler/sched-arch.txt b/Documentation/scheduler/sched-arch.txt
index 28aa107..b1b8587 100644
--- a/Documentation/scheduler/sched-arch.txt
+++ b/Documentation/scheduler/sched-arch.txt
@@ -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:
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f3eebc1..60e5e38 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -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.
*/
diff --git a/kernel/fork.c b/kernel/fork.c
index 2c8857e..743d48f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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_;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c46a011..8b51b2d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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();
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index e0b7ba9..418feb0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -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);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0987169..7a7db09 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -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 */
--
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