Linux內核中常用的一些延時方法

Linux內核中常用的一些延時方法

這些方法在以下路徑下定義：kernel/include/linux/delay.h

 

#ifndef _LINUX_DELAY_H

#define _LINUX_DELAY_H



/*

 * Copyright (C) 1993 Linus Torvalds

 *

 * Delay routines, using a pre-computed "loops_per_jiffy" value.

 */



#include <linux/kernel.h>



extern unsigned long loops_per_jiffy;



#include <asm/delay.h>



/*

 * Using udelay() for intervals greater than a few milliseconds can

 * risk overflow for high loops_per_jiffy (high bogomips) machines. The

 * mdelay() provides a wrapper to prevent this.  For delays greater

 * than MAX_UDELAY_MS milliseconds, the wrapper is used.  Architecture

 * specific values can be defined in asm-???/delay.h as an override.

 * The 2nd mdelay() definition ensures GCC will optimize away the 

 * while loop for the common cases where n <= MAX_UDELAY_MS  --  Paul G.

 */



#ifndef MAX_UDELAY_MS

#define MAX_UDELAY_MS	5

#endif



#ifndef mdelay

#define mdelay(n) (\

	(__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \

	({unsigned long __ms=(n); while (__ms--) udelay(1000);}))

#endif



#ifndef ndelay

static inline void ndelay(unsigned long x)

{

	udelay(DIV_ROUND_UP(x, 1000));

}

#define ndelay(x) ndelay(x)

#endif



extern unsigned long lpj_fine;

void calibrate_delay(void);

void msleep(unsigned int msecs);

unsigned long msleep_interruptible(unsigned int msecs);

void usleep_range(unsigned long min, unsigned long max);



static inline void ssleep(unsigned int seconds)

{

	msleep(seconds * 1000);

}



#endif /* defined(_LINUX_DELAY_H) */