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u64 get_jiffies_64(void)
{
unsigned long seq;
u64 ret;
do {
seq = read_seqbegin(&xtime_lock);
ret = jiffies_64;
}while(read_seqretry(&xtime_lock),seq));
return ret;
}
write_seqlock(&xtime_lock);
jiffies_64 += 1;
write_sequnlock(&xtime_lock);
/* some arch's have a small-data section that can be accessed register-relative
* but that can only take up to, say, 4-byte variables. jiffies being part of
* an 8-byte variable may not be correctly accessed unless we force the issue
*/
#define __jiffy_data __attribute__((section(".data")))
/*
* The 64-bit value is not atomic - you MUST NOT read it
* without sampling the sequence number in xtime_lock.
* get_jiffies_64() will do this for you as appropriate.
*/
extern u64 __jiffy_data jiffies_64;
extern unsigned long volatile __jiffy_data jiffies;
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void);
#else
static inline u64 get_jiffies_64(void)
{
return (u64)jiffies;
}
[/quote]真赞啊!!!谢谢!/* some arch's have a small-data section that can be accessed register-relative
* but that can only take up to, say, 4-byte variables. jiffies being part of
* an 8-byte variable may not be correctly accessed unless we force the issue
*/
#define __jiffy_data __attribute__((section(".data")))
/*
* The 64-bit value is not atomic - you MUST NOT read it
* without sampling the sequence number in xtime_lock.
* get_jiffies_64() will do this for you as appropriate.
*/
extern u64 __jiffy_data jiffies_64;
extern unsigned long volatile __jiffy_data jiffies;
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void);
#else
static inline u64 get_jiffies_64(void)
{
return (u64)jiffies;
}
{
unsigned long seq;
u64 ret;
do {
// 获取 顺序数
seq = read_seqbegin(&xtime_lock);
ret = jiffies_64;
// 如果之前获取的顺序数,与当前顺序数不一样(有写操作正在进行)。重新读取。
}while(read_seqretry(&xtime_lock),seq));
return ret;
}