sched: document profile=sleep requiring CONFIG_SCHEDSTATS

profile=sleep only works if CONFIG_SCHEDSTATS is set. This patch notes
the limitation in Documentation/kernel-parameters.txt and prints a
warning at boot-time if profile=sleep is used without CONFIG_SCHEDSTAT.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 0 deletions

diff --git a/kernel/profile.c b/kernel/profile.c
index 631b75c25d7e..5e95330e5120 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -60,6 +60,7 @@ static int __init profile_setup(char * str)
         int par;
 
         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
+#ifdef CONFIG_SCHEDSTATS
                 prof_on = SLEEP_PROFILING;
                 if (str[strlen(sleepstr)] == ',')
                         str += strlen(sleepstr) + 1;
@@ -68,6 +69,10 @@ static int __init profile_setup(char * str)
                 printk(KERN_INFO
                         "kernel sleep profiling enabled (shift: %ld)\n",
                         prof_shift);
+#else
+                printk(KERN_WARNING
+                        "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
+#endif /* CONFIG_SCHEDSTATS */
         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
                 prof_on = SCHED_PROFILING;
                 if (str[strlen(schedstr)] == ',')