perf sched: Use PTHREAD_STACK_MIN to avoid pthread_attr_setstacksize() fail

on ppc64:
/usr/include/bits/local_lim.h:#define PTHREAD_STACK_MIN 131072

therefore following set of commands:

gives:
perf.2.6.37test: builtin-sched.c:493: create_tasks: Assertion `!(err)' failed.

So make sure we do not set stack size lower than PTHREAD_STACK_MIN.

Cc: Ingo Molnar <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
LKML-Reference: <[e-mail]>
Signed-off-by: Jiri Pirko <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-sched.c

···
 
 	err = pthread_attr_init(&attr);
 	BUG_ON(err);
-	err = pthread_attr_setstacksize(&attr, (size_t)(16*1024));
+	err = pthread_attr_setstacksize(&attr,
+			(size_t) max(16 * 1024, PTHREAD_STACK_MIN));
 	BUG_ON(err);
 	err = pthread_mutex_lock(&start_work_mutex);
 	BUG_ON(err);