perf tools: Introduce dump_stack signal helper

To use in stdio based tools, like 'trace'.

Cc: Adrian Hunter <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Don Zickus <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/util.c

···
 void dump_stack(void) {}
 #endif
 
+void sighandler_dump_stack(int sig)
+{
+	psignal(sig, "perf");
+	dump_stack();
+	exit(sig);
+}
+
 void get_term_dimensions(struct winsize *ws)
 {
 	char *s = getenv("LINES");

tools/perf/util/util.h

···
 char *rtrim(char *s);
 
 void dump_stack(void);
+void sighandler_dump_stack(int sig);
 
 extern unsigned int page_size;
 extern int cacheline_size;