[patch] can't switch to jiffies clocksource

[Luming Yu <luming.yu@gmail.com>]

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Hello,

As this bug https://bugzilla.redhat.com/show_bug.cgi?id=496028,
echo jiffies > clocksource0/current_clocksource make system crash.
I reproduced the problem with upstream kernel.
The root cause is that jiffies is just a variable in memory,
it relies on other clock source to tick , and it never ticks on itself.

Please review, and apply.

**The patch is enclosed in text attachment*
**Using web client to send the patch* *
**below is for review, please apply attached  patch*/

Thanks,
Luming


Signed-off-by: Yu Luming <luming.yu@intel.com>

 clocksource.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)


iff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index ecfd7b5..bdffe43 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -507,8 +507,9 @@ static ssize_t sysfs_override_clocksource(struct
sys_device *dev,
 		/* try to select it: */
 		list_for_each_entry(cs, &clocksource_list, list) {
 			if (strlen(cs->name) == len &&
-			    !strcmp(cs->name, override_name))
-				ovr = cs;
+			    !strcmp(cs->name, override_name) &&
+				cs != &clocksource_jiffies)
+					ovr = cs;
 		}
 	}

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diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index ecfd7b5..bdffe43 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -507,8 +507,9 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
 		/* try to select it: */
 		list_for_each_entry(cs, &clocksource_list, list) {
 			if (strlen(cs->name) == len &&
-			    !strcmp(cs->name, override_name))
-				ovr = cs;
+			    !strcmp(cs->name, override_name) &&
+				cs != &clocksource_jiffies)
+					ovr = cs;
 		}
 	}