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tracing: add comment for use of double __builtin_consant_p

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Impact: documentation

The use of the double __builtin_contant_p checks in the event_trace_printk
can be confusing to developers and reviewers. This patch adds a comment
to explain why it is there.

Requested-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
LKML-Reference: <20090313122235.43EB.A69D9226@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This commit is contained in:
Steven Rostedt
2009-03-13 00:12:52 -04:00
parent eb1871f343
commit bdc067582b
1 changed files with 5 additions and 0 deletions
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5
kernel/trace/trace.h
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@@ -776,6 +776,11 @@ extern struct ftrace_event_call __stop_ftrace_events[];
extern const char *__start___trace_bprintk_fmt[]; extern const char *__start___trace_bprintk_fmt[];
extern const char *__stop___trace_bprintk_fmt[]; extern const char *__stop___trace_bprintk_fmt[];
/*
* The double __builtin_constant_p is because gcc will give us an error
* if we try to allocate the static variable to fmt if it is not a
* constant. Even with the outer if statement optimizing out.
*/
#define event_trace_printk(ip, fmt, args...) \ #define event_trace_printk(ip, fmt, args...) \
do { \ do { \
__trace_printk_check_format(fmt, ##args); \ __trace_printk_check_format(fmt, ##args); \