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printk: introduce printk_once()

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This pattern shows up frequently in the kernel:

  static int once = 1;
  ...

		if (once) {
			once = 0;
			printk(KERN_ERR "message\n");
		}
  ...

So add a printk_once() helper macro that reduces this to a single line
of:

		printk_once(KERN_ERR "message\n");

It works analogously to WARN_ONCE() & friends. (We use a macro not
an inline because vararg expansion in inlines looks awkward and the
macro is simple enough.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2009-02-05 13:45:43 +01:00
parent eda58a85ec
commit f036be96dd
1 changed files with 17 additions and 0 deletions
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17
include/linux/kernel.h
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@ -242,6 +242,19 @@ extern struct ratelimit_state printk_ratelimit_state;
extern int printk_ratelimit(void);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msec);
/*
* Print a one-time message (analogous to WARN_ONCE() et al):
*/
#define printk_once(x...) ({ \
static int __print_once = 1; \
\
if (__print_once) { \
__print_once = 0; \
printk(x); \
} \
})
#else
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
@ -253,6 +266,10 @@ static inline int printk_ratelimit(void) { return 0; }
static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \
unsigned int interval_msec) \
{ return false; }
/* No effect, but we still get type checking even in the !PRINTK case: */
#define printk_once(x...) printk(x)
#endif
extern int printk_needs_cpu(int cpu);