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authorThomas Gleixner <tglx@linutronix.de>2010-03-12 17:34:14 +0100
committerThomas Gleixner <tglx@linutronix.de>2010-03-12 19:10:29 +0100
commit80a05b9ffa7dc13f6693902dd8999a2b61a3a0d7 (patch)
tree5612eeb26804b135de66779d1a00eaf35a4ceca1 /kernel/time/tick-oneshot.c
parentad6759fbf35d104dbf573cd6f4c6784ad6823f7e (diff)
downloadlinux-80a05b9ffa7dc13f6693902dd8999a2b61a3a0d7.tar.bz2
clockevents: Sanitize min_delta_ns adjustment and prevent overflows
The current logic which handles clock events programming failures can increase min_delta_ns unlimited and even can cause overflows. Sanitize it by: - prevent zero increase when min_delta_ns == 1 - limiting min_delta_ns to a jiffie - bail out if the jiffie limit is hit - add retries stats for /proc/timer_list so we can gather data Reported-by: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/tick-oneshot.c')
-rw-r--r--kernel/time/tick-oneshot.c52
1 files changed, 40 insertions, 12 deletions
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index 0a8a213016f0..aada0e52680a 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -22,6 +22,29 @@
#include "tick-internal.h"
+/* Limit min_delta to a jiffie */
+#define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ)
+
+static int tick_increase_min_delta(struct clock_event_device *dev)
+{
+ /* Nothing to do if we already reached the limit */
+ if (dev->min_delta_ns >= MIN_DELTA_LIMIT)
+ return -ETIME;
+
+ if (dev->min_delta_ns < 5000)
+ dev->min_delta_ns = 5000;
+ else
+ dev->min_delta_ns += dev->min_delta_ns >> 1;
+
+ if (dev->min_delta_ns > MIN_DELTA_LIMIT)
+ dev->min_delta_ns = MIN_DELTA_LIMIT;
+
+ printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
+ dev->name ? dev->name : "?",
+ (unsigned long long) dev->min_delta_ns);
+ return 0;
+}
+
/**
* tick_program_event internal worker function
*/
@@ -37,23 +60,28 @@ int tick_dev_program_event(struct clock_event_device *dev, ktime_t expires,
if (!ret || !force)
return ret;
+ dev->retries++;
/*
- * We tried 2 times to program the device with the given
- * min_delta_ns. If that's not working then we double it
+ * We tried 3 times to program the device with the given
+ * min_delta_ns. If that's not working then we increase it
* and emit a warning.
*/
if (++i > 2) {
/* Increase the min. delta and try again */
- if (!dev->min_delta_ns)
- dev->min_delta_ns = 5000;
- else
- dev->min_delta_ns += dev->min_delta_ns >> 1;
-
- printk(KERN_WARNING
- "CE: %s increasing min_delta_ns to %llu nsec\n",
- dev->name ? dev->name : "?",
- (unsigned long long) dev->min_delta_ns << 1);
-
+ if (tick_increase_min_delta(dev)) {
+ /*
+ * Get out of the loop if min_delta_ns
+ * hit the limit already. That's
+ * better than staying here forever.
+ *
+ * We clear next_event so we have a
+ * chance that the box survives.
+ */
+ printk(KERN_WARNING
+ "CE: Reprogramming failure. Giving up\n");
+ dev->next_event.tv64 = KTIME_MAX;
+ return -ETIME;
+ }
i = 0;
}