uclinux-2008R1-RC8(bf561)到VDSP5的移植(26)：smp_processor_id

 

  

smp_processor_id是在include/linux/smp.h中定义的一个宏：

# define smp_processor_id() raw_smp_processor_id()

在此之前还有一段说明：

 

/*

 * 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.

 */

那么raw_smp_processor_id又是何方神圣？从定义和注释可以认为这个宏应该用于取得当前运行代码的CPU序号，查了下linux-2.6.19的代码，在asm/smp.h中可以验证这一点，而VDSP5提供了一个叫adi_core_id的函数：

adi_core_id

---

Identify caller’s core

Synopsis

#include <ccblkfn.h>

int adi_core_id(void);

Description

The adi_core_id function returns a numeric value indicating which processor core is executing the call to the function. This function is most useful on multi-core processors, when the caller is a function shared between both cores, but which needs to perform different actions (or access different data) depending on the core executing it.

The function returns a zero value when executed by Core A, and a value of one when executed on Core B.

Error Conditions

The adi_core_id function does not return an error condition.

Example

#include <ccblkfn.h>

const char *core_name(void)

{

      if (adi_core_id() == 0)

         return "Core A";

      else

         return "Core B";

}

因此我们在asm/smp.h中添加如下定义：

 

/*

 * This function is needed by all SMP systems. It must _always_ be valid

 * from the initial startup. We map APIC_BASE very early in page_setup(),

 * so this is correct in the x86 case.

 */

#define raw_smp_processor_id() (adi_core_id())