summaryrefslogtreecommitdiffstats
path: root/kernel/time
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/clocksource.c52
1 files changed, 42 insertions, 10 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index b8a14d2fb5ba..b7e52a642948 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -107,7 +107,7 @@ static u64 suspend_start;
* This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
* a lower bound for cs->uncertainty_margin values when registering clocks.
*/
-#define WATCHDOG_MAX_SKEW (50 * NSEC_PER_USEC)
+#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC)
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
static void clocksource_watchdog_work(struct work_struct *work);
@@ -199,23 +199,30 @@ void clocksource_mark_unstable(struct clocksource *cs)
spin_unlock_irqrestore(&watchdog_lock, flags);
}
-ulong max_cswd_read_retries = 3;
+ulong max_cswd_read_retries = 2;
module_param(max_cswd_read_retries, ulong, 0644);
EXPORT_SYMBOL_GPL(max_cswd_read_retries);
static int verify_n_cpus = 8;
module_param(verify_n_cpus, int, 0644);
-static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
+enum wd_read_status {
+ WD_READ_SUCCESS,
+ WD_READ_UNSTABLE,
+ WD_READ_SKIP
+};
+
+static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
{
unsigned int nretries;
- u64 wd_end, wd_delta;
- int64_t wd_delay;
+ u64 wd_end, wd_end2, wd_delta;
+ int64_t wd_delay, wd_seq_delay;
for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
local_irq_disable();
*wdnow = watchdog->read(watchdog);
*csnow = cs->read(cs);
wd_end = watchdog->read(watchdog);
+ wd_end2 = watchdog->read(watchdog);
local_irq_enable();
wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
@@ -226,13 +233,34 @@ static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
smp_processor_id(), watchdog->name, nretries);
}
- return true;
+ return WD_READ_SUCCESS;
}
+
+ /*
+ * Now compute delay in consecutive watchdog read to see if
+ * there is too much external interferences that cause
+ * significant delay in reading both clocksource and watchdog.
+ *
+ * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
+ * report system busy, reinit the watchdog and skip the current
+ * watchdog test.
+ */
+ wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
+ wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
+ if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
+ goto skip_test;
}
pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
smp_processor_id(), watchdog->name, wd_delay, nretries);
- return false;
+ return WD_READ_UNSTABLE;
+
+skip_test:
+ pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
+ smp_processor_id(), watchdog->name, wd_seq_delay);
+ pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
+ cs->name, wd_delay);
+ return WD_READ_SKIP;
}
static u64 csnow_mid;
@@ -356,6 +384,7 @@ static void clocksource_watchdog(struct timer_list *unused)
int next_cpu, reset_pending;
int64_t wd_nsec, cs_nsec;
struct clocksource *cs;
+ enum wd_read_status read_ret;
u32 md;
spin_lock(&watchdog_lock);
@@ -373,9 +402,12 @@ static void clocksource_watchdog(struct timer_list *unused)
continue;
}
- if (!cs_watchdog_read(cs, &csnow, &wdnow)) {
- /* Clock readout unreliable, so give it up. */
- __clocksource_unstable(cs);
+ read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
+
+ if (read_ret != WD_READ_SUCCESS) {
+ if (read_ret == WD_READ_UNSTABLE)
+ /* Clock readout unreliable, so give it up. */
+ __clocksource_unstable(cs);
continue;
}