aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2009-12-11 20:49:09 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-11 20:49:09 -0800
commit3070f27d6ecb69364e7cffe16c8b15e1b8ef41dd (patch)
tree6a624eb764265b67b2765b978c749fbe08871886
parent1e57c2186fc204ecd5e47f279d00eba3c3db245c (diff)
parente9c0748b687aa70179a9e6d8ffc24b2874fe350b (diff)
downloadmrst-s0i3-test-3070f27d6ecb69364e7cffe16c8b15e1b8ef41dd.tar.gz
mrst-s0i3-test-3070f27d6ecb69364e7cffe16c8b15e1b8ef41dd.tar.xz
mrst-s0i3-test-3070f27d6ecb69364e7cffe16c8b15e1b8ef41dd.zip
Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: itimer: Fix the itimer trace print format hrtimer: move timer stats helper functions to hrtimer.c hrtimer: Tune hrtimer_interrupt hang logic
-rw-r--r--include/linux/hrtimer.h56
-rw-r--r--include/trace/events/timer.h8
-rw-r--r--kernel/hrtimer.c121
-rw-r--r--kernel/time/timer_list.c5
4 files changed, 94 insertions, 96 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 9bace4b9f4f..af634e95871 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -162,10 +162,11 @@ struct hrtimer_clock_base {
* @expires_next: absolute time of the next event which was scheduled
* via clock_set_next_event()
* @hres_active: State of high resolution mode
- * @check_clocks: Indictator, when set evaluate time source and clock
- * event devices whether high resolution mode can be
- * activated.
- * @nr_events: Total number of timer interrupt events
+ * @hang_detected: The last hrtimer interrupt detected a hang
+ * @nr_events: Total number of hrtimer interrupt events
+ * @nr_retries: Total number of hrtimer interrupt retries
+ * @nr_hangs: Total number of hrtimer interrupt hangs
+ * @max_hang_time: Maximum time spent in hrtimer_interrupt
*/
struct hrtimer_cpu_base {
spinlock_t lock;
@@ -173,7 +174,11 @@ struct hrtimer_cpu_base {
#ifdef CONFIG_HIGH_RES_TIMERS
ktime_t expires_next;
int hres_active;
+ int hang_detected;
unsigned long nr_events;
+ unsigned long nr_retries;
+ unsigned long nr_hangs;
+ ktime_t max_hang_time;
#endif
};
@@ -435,47 +440,4 @@ extern u64 ktime_divns(const ktime_t kt, s64 div);
/* Show pending timers: */
extern void sysrq_timer_list_show(void);
-/*
- * Timer-statistics info:
- */
-#ifdef CONFIG_TIMER_STATS
-
-extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
- void *timerf, char *comm,
- unsigned int timer_flag);
-
-static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
-{
- if (likely(!timer_stats_active))
- return;
- timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
- timer->function, timer->start_comm, 0);
-}
-
-extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
- void *addr);
-
-static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
-{
- __timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
-}
-
-static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
-{
- timer->start_site = NULL;
-}
-#else
-static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
-{
-}
-
-static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
-{
-}
-
-static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
-{
-}
-#endif
-
#endif
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index e5ce87a0498..9496b965d62 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -301,8 +301,8 @@ TRACE_EVENT(itimer_state,
__entry->interval_usec = value->it_interval.tv_usec;
),
- TP_printk("which=%d expires=%lu it_value=%lu.%lu it_interval=%lu.%lu",
- __entry->which, __entry->expires,
+ TP_printk("which=%d expires=%llu it_value=%ld.%ld it_interval=%ld.%ld",
+ __entry->which, (unsigned long long)__entry->expires,
__entry->value_sec, __entry->value_usec,
__entry->interval_sec, __entry->interval_usec)
);
@@ -331,8 +331,8 @@ TRACE_EVENT(itimer_expire,
__entry->pid = pid_nr(pid);
),
- TP_printk("which=%d pid=%d now=%lu", __entry->which,
- (int) __entry->pid, __entry->now)
+ TP_printk("which=%d pid=%d now=%llu", __entry->which,
+ (int) __entry->pid, (unsigned long long)__entry->now)
);
#endif /* _TRACE_TIMER_H */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ede52770812..d2f9239dc6b 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -557,7 +557,7 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
static int hrtimer_reprogram(struct hrtimer *timer,
struct hrtimer_clock_base *base)
{
- ktime_t *expires_next = &__get_cpu_var(hrtimer_bases).expires_next;
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
int res;
@@ -582,7 +582,16 @@ static int hrtimer_reprogram(struct hrtimer *timer,
if (expires.tv64 < 0)
return -ETIME;
- if (expires.tv64 >= expires_next->tv64)
+ if (expires.tv64 >= cpu_base->expires_next.tv64)
+ return 0;
+
+ /*
+ * If a hang was detected in the last timer interrupt then we
+ * do not schedule a timer which is earlier than the expiry
+ * which we enforced in the hang detection. We want the system
+ * to make progress.
+ */
+ if (cpu_base->hang_detected)
return 0;
/*
@@ -590,7 +599,7 @@ static int hrtimer_reprogram(struct hrtimer *timer,
*/
res = tick_program_event(expires, 0);
if (!IS_ERR_VALUE(res))
- *expires_next = expires;
+ cpu_base->expires_next = expires;
return res;
}
@@ -747,17 +756,33 @@ static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }
#endif /* CONFIG_HIGH_RES_TIMERS */
-#ifdef CONFIG_TIMER_STATS
-void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer, void *addr)
+static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
+#ifdef CONFIG_TIMER_STATS
if (timer->start_site)
return;
-
- timer->start_site = addr;
+ timer->start_site = __builtin_return_address(0);
memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
timer->start_pid = current->pid;
+#endif
}
+
+static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
+{
+#ifdef CONFIG_TIMER_STATS
+ timer->start_site = NULL;
+#endif
+}
+
+static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
+{
+#ifdef CONFIG_TIMER_STATS
+ if (likely(!timer_stats_active))
+ return;
+ timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
+ timer->function, timer->start_comm, 0);
#endif
+}
/*
* Counterpart to lock_hrtimer_base above:
@@ -1217,30 +1242,6 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
#ifdef CONFIG_HIGH_RES_TIMERS
-static int force_clock_reprogram;
-
-/*
- * After 5 iteration's attempts, we consider that hrtimer_interrupt()
- * is hanging, which could happen with something that slows the interrupt
- * such as the tracing. Then we force the clock reprogramming for each future
- * hrtimer interrupts to avoid infinite loops and use the min_delta_ns
- * threshold that we will overwrite.
- * The next tick event will be scheduled to 3 times we currently spend on
- * hrtimer_interrupt(). This gives a good compromise, the cpus will spend
- * 1/4 of their time to process the hrtimer interrupts. This is enough to
- * let it running without serious starvation.
- */
-
-static inline void
-hrtimer_interrupt_hanging(struct clock_event_device *dev,
- ktime_t try_time)
-{
- force_clock_reprogram = 1;
- dev->min_delta_ns = (unsigned long)try_time.tv64 * 3;
- printk(KERN_WARNING "hrtimer: interrupt too slow, "
- "forcing clock min delta to %llu ns\n",
- (unsigned long long) dev->min_delta_ns);
-}
/*
* High resolution timer interrupt
* Called with interrupts disabled
@@ -1249,21 +1250,15 @@ void hrtimer_interrupt(struct clock_event_device *dev)
{
struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
struct hrtimer_clock_base *base;
- ktime_t expires_next, now;
- int nr_retries = 0;
- int i;
+ ktime_t expires_next, now, entry_time, delta;
+ int i, retries = 0;
BUG_ON(!cpu_base->hres_active);
cpu_base->nr_events++;
dev->next_event.tv64 = KTIME_MAX;
- retry:
- /* 5 retries is enough to notice a hang */
- if (!(++nr_retries % 5))
- hrtimer_interrupt_hanging(dev, ktime_sub(ktime_get(), now));
-
- now = ktime_get();
-
+ entry_time = now = ktime_get();
+retry:
expires_next.tv64 = KTIME_MAX;
spin_lock(&cpu_base->lock);
@@ -1325,10 +1320,48 @@ void hrtimer_interrupt(struct clock_event_device *dev)
spin_unlock(&cpu_base->lock);
/* Reprogramming necessary ? */
- if (expires_next.tv64 != KTIME_MAX) {
- if (tick_program_event(expires_next, force_clock_reprogram))
- goto retry;
+ if (expires_next.tv64 == KTIME_MAX ||
+ !tick_program_event(expires_next, 0)) {
+ cpu_base->hang_detected = 0;
+ return;
}
+
+ /*
+ * The next timer was already expired due to:
+ * - tracing
+ * - long lasting callbacks
+ * - being scheduled away when running in a VM
+ *
+ * We need to prevent that we loop forever in the hrtimer
+ * interrupt routine. We give it 3 attempts to avoid
+ * overreacting on some spurious event.
+ */
+ now = ktime_get();
+ cpu_base->nr_retries++;
+ if (++retries < 3)
+ goto retry;
+ /*
+ * Give the system a chance to do something else than looping
+ * here. We stored the entry time, so we know exactly how long
+ * we spent here. We schedule the next event this amount of
+ * time away.
+ */
+ cpu_base->nr_hangs++;
+ cpu_base->hang_detected = 1;
+ delta = ktime_sub(now, entry_time);
+ if (delta.tv64 > cpu_base->max_hang_time.tv64)
+ cpu_base->max_hang_time = delta;
+ /*
+ * Limit it to a sensible value as we enforce a longer
+ * delay. Give the CPU at least 100ms to catch up.
+ */
+ if (delta.tv64 > 100 * NSEC_PER_MSEC)
+ expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
+ else
+ expires_next = ktime_add(now, delta);
+ tick_program_event(expires_next, 1);
+ printk_once(KERN_WARNING "hrtimer: interrupt took %llu ns\n",
+ ktime_to_ns(delta));
}
/*
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 665c76edbf1..9d80db4747d 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -150,6 +150,9 @@ static void print_cpu(struct seq_file *m, int cpu, u64 now)
P_ns(expires_next);
P(hres_active);
P(nr_events);
+ P(nr_retries);
+ P(nr_hangs);
+ P_ns(max_hang_time);
#endif
#undef P
#undef P_ns
@@ -254,7 +257,7 @@ static int timer_list_show(struct seq_file *m, void *v)
u64 now = ktime_to_ns(ktime_get());
int cpu;
- SEQ_printf(m, "Timer List Version: v0.4\n");
+ SEQ_printf(m, "Timer List Version: v0.5\n");
SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);