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sched/preempt, locking: Rework local_bh_{dis,en}able()

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Currently local_bh_disable() is out-of-line for no apparent reason.
So inline it to save a few cycles on call/return nonsense, the
function body is a single add on x86 (a few loads and store extra on
load/store archs).

Also expose two new local_bh functions:

  __local_bh_{dis,en}able_ip(unsigned long ip, unsigned int cnt);

Which implement the actual local_bh_{dis,en}able() behaviour.

The next patch uses the exposed @cnt argument to optimize bh lock
functions.

With build fixes from Jacob Pan.

Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith <bitbucket@online.de>
Cc: hpa@zytor.com
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: lenb@kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2013-11-19 16:13:38 +01:00 committed by Ingo Molnar
parent 10b033d434
commit 0bd3a173d7
4 changed files with 36 additions and 33 deletions
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32
include/linux/bottom_half.h
View File

@ -1,9 +1,35 @@
#ifndef _LINUX_BH_H
#define _LINUX_BH_H
extern void local_bh_disable(void);
#include <linux/preempt.h>
#include <linux/preempt_mask.h>
#ifdef CONFIG_TRACE_IRQFLAGS
extern void __local_bh_disable_ip(unsigned long ip, unsigned int cnt);
#else
static __always_inline void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
{
preempt_count_add(cnt);
barrier();
}
#endif
static inline void local_bh_disable(void)
{
__local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
}
extern void _local_bh_enable(void);
extern void local_bh_enable(void);
extern void local_bh_enable_ip(unsigned long ip);
extern void __local_bh_enable_ip(unsigned long ip, unsigned int cnt);
static inline void local_bh_enable_ip(unsigned long ip)
{
__local_bh_enable_ip(ip, SOFTIRQ_DISABLE_OFFSET);
}
static inline void local_bh_enable(void)
{
__local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
}
#endif /* _LINUX_BH_H */

1
include/linux/hardirq.h
View File

@ -5,6 +5,7 @@
#include <linux/lockdep.h>
#include <linux/ftrace_irq.h>
#include <linux/vtime.h>
#include <asm/hardirq.h>
extern void synchronize_irq(unsigned int irq);

1
include/linux/preempt_mask.h
View File

@ -2,7 +2,6 @@
#define LINUX_PREEMPT_MASK_H
#include <linux/preempt.h>
#include <asm/hardirq.h>
/*
* We put the hardirq and softirq counter into the preemption

35
kernel/softirq.c
View File

@ -89,7 +89,7 @@ static void wakeup_softirqd(void)
* where hardirqs are disabled legitimately:
*/
#ifdef CONFIG_TRACE_IRQFLAGS
static void __local_bh_disable(unsigned long ip, unsigned int cnt)
void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
{
unsigned long flags;
@ -114,21 +114,9 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt)
if (preempt_count() == cnt)
trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
}
#else /* !CONFIG_TRACE_IRQFLAGS */
static inline void __local_bh_disable(unsigned long ip, unsigned int cnt)
{
preempt_count_add(cnt);
barrier();
}
EXPORT_SYMBOL(__local_bh_disable_ip);
#endif /* CONFIG_TRACE_IRQFLAGS */
void local_bh_disable(void)
{
__local_bh_disable(_RET_IP_, SOFTIRQ_DISABLE_OFFSET);
}
EXPORT_SYMBOL(local_bh_disable);
static void __local_bh_enable(unsigned int cnt)
{
WARN_ON_ONCE(!irqs_disabled());
@ -151,7 +139,7 @@ void _local_bh_enable(void)
EXPORT_SYMBOL(_local_bh_enable);
static inline void _local_bh_enable_ip(unsigned long ip)
void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
{
WARN_ON_ONCE(in_irq() || irqs_disabled());
#ifdef CONFIG_TRACE_IRQFLAGS
@ -166,7 +154,7 @@ static inline void _local_bh_enable_ip(unsigned long ip)
* Keep preemption disabled until we are done with
* softirq processing:
*/
preempt_count_sub(SOFTIRQ_DISABLE_OFFSET - 1);
preempt_count_sub(cnt - 1);
if (unlikely(!in_interrupt() && local_softirq_pending())) {
/*
@ -182,18 +170,7 @@ static inline void _local_bh_enable_ip(unsigned long ip)
#endif
preempt_check_resched();
}
void local_bh_enable(void)
{
_local_bh_enable_ip(_RET_IP_);
}
EXPORT_SYMBOL(local_bh_enable);
void local_bh_enable_ip(unsigned long ip)
{
_local_bh_enable_ip(ip);
}
EXPORT_SYMBOL(local_bh_enable_ip);
EXPORT_SYMBOL(__local_bh_enable_ip);
/*
* We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
@ -230,7 +207,7 @@ asmlinkage void __do_softirq(void)
pending = local_softirq_pending();
account_irq_enter_time(current);
__local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);
__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
lockdep_softirq_enter();
cpu = smp_processor_id();