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authorjohn stultz <johnstul@us.ibm.com>2009-01-21 22:53:22 -0700
committerThomas Gleixner <tglx@linutronix.de>2009-06-11 11:24:52 +0200
commit3f68535adad8dd89499505a65fb25d0e02d118cc (patch)
treeb347c3901d2d590d8c2b8c3be993ef20b278e61f /kernel/time
parent7d27558c4138ac6b3684dea35c2f4379b940a7dd (diff)
clocksource: sanity check sysfs clocksource changes
Thomas, Andrew and Ingo pointed out that we don't have any safety checks in the clocksource sysfs entries to make sure sysadmins don't try to change the clocksource to a non high-res timer capable clocksource (such as jiffies) when high-res timers (HRT) is enabled. Doing so will likely hang a system. Correct this by filtering non HRT clocksources from available_clocksources and not accepting non HRT clocksources with HRT enabled. Signed-off-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/clocksource.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 80189f6f1c5a..18b9f5da4ee9 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -30,6 +30,7 @@
#include <linux/module.h>
#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
#include <linux/tick.h>
+#include <linux/hrtimer.h>
void timecounter_init(struct timecounter *tc,
const struct cyclecounter *cc,
@@ -509,6 +510,18 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
}
}
+ /*
+ * Check to make sure we don't switch to a non-HRT usable
+ * clocksource if HRT is enabled and running
+ */
+ if (hrtimer_hres_active() &&
+ !(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) {
+ printk(KERN_WARNING "%s clocksource is not HRT compatible. "
+ "Cannot switch while in HRT mode\n", ovr->name);
+ ovr = NULL;
+ override_name[0] = 0;
+ }
+
/* Reselect, when the override name has changed */
if (ovr != clocksource_override) {
clocksource_override = ovr;
@@ -537,7 +550,10 @@ sysfs_show_available_clocksources(struct sys_device *dev,
spin_lock_irq(&clocksource_lock);
list_for_each_entry(src, &clocksource_list, list) {
- count += snprintf(buf + count,
+ /* Don't show non-HRES clocksource if HRES is enabled */
+ if (!hrtimer_hres_active() ||
+ (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+ count += snprintf(buf + count,
max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
"%s ", src->name);
}