kernel-fxtec-pro1x/include/linux/smp.h
Thomas Gleixner 8b0b1db013 remove put_cpu_no_resched()
put_cpu_no_resched() is an optimization of put_cpu() which unfortunately
can cause high latencies.

The nfs iostats code uses put_cpu_no_resched() in a code sequence where a
reschedule request caused by an interrupt between the get_cpu() and the
put_cpu_no_resched() can delay the reschedule for at least HZ.

The other users of put_cpu_no_resched() optimize correctly in interrupt
code, but there is no real harm in using the put_cpu() function which is
an alias for preempt_enable().  The extra check of the preemmpt count is
not as critical as the potential source of missing a reschedule.

Debugged in the preempt-rt tree and verified in mainline.

Impact: remove a high latency source

[akpm@linux-foundation.org: build fix]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-16 19:47:48 -07:00

189 lines
4.8 KiB
C

#ifndef __LINUX_SMP_H
#define __LINUX_SMP_H
/*
* Generic SMP support
* Alan Cox. <alan@redhat.com>
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/cpumask.h>
extern void cpu_idle(void);
struct call_single_data {
struct list_head list;
void (*func) (void *info);
void *info;
u16 flags;
u16 priv;
};
/* total number of cpus in this system (may exceed NR_CPUS) */
extern unsigned int total_cpus;
int smp_call_function_single(int cpuid, void (*func) (void *info), void *info,
int wait);
#ifdef CONFIG_SMP
#include <linux/preempt.h>
#include <linux/kernel.h>
#include <linux/compiler.h>
#include <linux/thread_info.h>
#include <asm/smp.h>
/*
* main cross-CPU interfaces, handles INIT, TLB flush, STOP, etc.
* (defined in asm header):
*/
/*
* stops all CPUs but the current one:
*/
extern void smp_send_stop(void);
/*
* sends a 'reschedule' event to another CPU:
*/
extern void smp_send_reschedule(int cpu);
/*
* Prepare machine for booting other CPUs.
*/
extern void smp_prepare_cpus(unsigned int max_cpus);
/*
* Bring a CPU up
*/
extern int __cpu_up(unsigned int cpunum);
/*
* Final polishing of CPUs
*/
extern void smp_cpus_done(unsigned int max_cpus);
/*
* Call a function on all other processors
*/
int smp_call_function(void(*func)(void *info), void *info, int wait);
void smp_call_function_many(const struct cpumask *mask,
void (*func)(void *info), void *info, bool wait);
/* Deprecated: Use smp_call_function_many which takes a pointer to the mask. */
static inline int
smp_call_function_mask(cpumask_t mask, void(*func)(void *info), void *info,
int wait)
{
smp_call_function_many(&mask, func, info, wait);
return 0;
}
void __smp_call_function_single(int cpuid, struct call_single_data *data,
int wait);
/*
* Generic and arch helpers
*/
#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
void generic_smp_call_function_single_interrupt(void);
void generic_smp_call_function_interrupt(void);
void ipi_call_lock(void);
void ipi_call_unlock(void);
void ipi_call_lock_irq(void);
void ipi_call_unlock_irq(void);
#endif
/*
* Call a function on all processors
*/
int on_each_cpu(void (*func) (void *info), void *info, int wait);
#define MSG_ALL_BUT_SELF 0x8000 /* Assume <32768 CPU's */
#define MSG_ALL 0x8001
#define MSG_INVALIDATE_TLB 0x0001 /* Remote processor TLB invalidate */
#define MSG_STOP_CPU 0x0002 /* Sent to shut down slave CPU's
* when rebooting
*/
#define MSG_RESCHEDULE 0x0003 /* Reschedule request from master CPU*/
#define MSG_CALL_FUNCTION 0x0004 /* Call function on all other CPUs */
/*
* Mark the boot cpu "online" so that it can call console drivers in
* printk() and can access its per-cpu storage.
*/
void smp_prepare_boot_cpu(void);
extern unsigned int setup_max_cpus;
#else /* !SMP */
static inline void smp_send_stop(void) { }
/*
* These macros fold the SMP functionality into a single CPU system
*/
#define raw_smp_processor_id() 0
static inline int up_smp_call_function(void (*func)(void *), void *info)
{
return 0;
}
#define smp_call_function(func, info, wait) \
(up_smp_call_function(func, info))
#define on_each_cpu(func,info,wait) \
({ \
local_irq_disable(); \
func(info); \
local_irq_enable(); \
0; \
})
static inline void smp_send_reschedule(int cpu) { }
#define num_booting_cpus() 1
#define smp_prepare_boot_cpu() do {} while (0)
#define smp_call_function_mask(mask, func, info, wait) \
(up_smp_call_function(func, info))
#define smp_call_function_many(mask, func, info, wait) \
(up_smp_call_function(func, info))
static inline void init_call_single_data(void)
{
}
#endif /* !SMP */
/*
* smp_processor_id(): get the current CPU ID.
*
* if DEBUG_PREEMPT is enabled the we check whether it is
* used in a preemption-safe way. (smp_processor_id() is safe
* if it's used in a preemption-off critical section, or in
* a thread that is bound to the current CPU.)
*
* NOTE: raw_smp_processor_id() is for internal use only
* (smp_processor_id() is the preferred variant), but in rare
* instances it might also be used to turn off false positives
* (i.e. smp_processor_id() use that the debugging code reports but
* which use for some reason is legal). Don't use this to hack around
* the warning message, as your code might not work under PREEMPT.
*/
#ifdef CONFIG_DEBUG_PREEMPT
extern unsigned int debug_smp_processor_id(void);
# define smp_processor_id() debug_smp_processor_id()
#else
# define smp_processor_id() raw_smp_processor_id()
#endif
#define get_cpu() ({ preempt_disable(); smp_processor_id(); })
#define put_cpu() preempt_enable()
/*
* Callback to arch code if there's nosmp or maxcpus=0 on the
* boot command line:
*/
extern void arch_disable_smp_support(void);
void smp_setup_processor_id(void);
#endif /* __LINUX_SMP_H */