From: Steven Rostedt Date: Fri, 13 Mar 2009 04:12:52 +0000 (-0400) Subject: tracing: add comment for use of double __builtin_consant_p X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=bdc067582b8b71c7771bab076bbc51569c594fb4;p=linux-beck.git tracing: add comment for use of double __builtin_consant_p 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 LKML-Reference: <20090313122235.43EB.A69D9226@jp.fujitsu.com> Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 35cfa7bbaf38..67595b8f0f15 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -776,6 +776,11 @@ extern struct ftrace_event_call __stop_ftrace_events[]; extern const char *__start___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...) \ do { \ __trace_printk_check_format(fmt, ##args); \