Thomas Gleixner <[email protected]> wrote:
> On Fri, 10 Oct 2008, Thomas Gleixner wrote:
>> On Fri, 10 Oct 2008, Elias Oltmanns wrote:
[...]
>> > This particular one is in
>> > drivers/net/wireless/ath5k/phy.c:ath5k_hw_noise_floor_calibration()
>> > which is called from ath5k_calibrate(), the callback executed every ten
>> > seconds in softirq context. Could this have anything to do with our
>>
>> That makes sense. The timer expires early events are multiples of 10s
>> apart.
>
> Ok, I thought more about it and aside of the fact that the ath5k is
> doing something nasty, you unearthed a weakness in the broadcast code.
>
> Can you please try the following:
>
> Compile the acpi_processor module in to the kernel
> (CONFIG_ACPI_PROCESSOR=y) and add processor.max_cstate=1 to the kernel
> command line. If I analysed the problem correctly this will make the
> jiffies problem go away. I'm working on a fix.
Spot on, it does go away regardless whether NO_HZ or HIGH_RES are
enabled or disabled. Looking forward to testing your fix ;-).
Regards,
Elias
On Sat, 11 Oct 2008, Elias Oltmanns wrote:
> > Compile the acpi_processor module in to the kernel
> > (CONFIG_ACPI_PROCESSOR=y) and add processor.max_cstate=1 to the kernel
> > command line. If I analysed the problem correctly this will make the
> > jiffies problem go away. I'm working on a fix.
>
> Spot on, it does go away regardless whether NO_HZ or HIGH_RES are
> enabled or disabled. Looking forward to testing your fix ;-).
Here you go.
tglx
---
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 98921a3..cb271ce 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -96,9 +96,11 @@ extern cpumask_t *tick_get_broadcast_oneshot_mask(void);
extern void tick_clock_notify(void);
extern int tick_check_oneshot_change(int allow_nohz);
extern struct tick_sched *tick_get_tick_sched(int cpu);
+extern void tick_check_idle(int cpu);
# else
static inline void tick_clock_notify(void) { }
static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
+static inline void tick_check_idle(int cpu) { }
# endif
#else /* CONFIG_GENERIC_CLOCKEVENTS */
@@ -111,21 +113,17 @@ static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
# ifdef CONFIG_NO_HZ
extern void tick_nohz_stop_sched_tick(int inidle);
extern void tick_nohz_restart_sched_tick(void);
-extern void tick_nohz_update_jiffies(void);
extern ktime_t tick_nohz_get_sleep_length(void);
-extern void tick_nohz_stop_idle(int cpu);
extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
# else
static inline void tick_nohz_stop_sched_tick(int inidle) { }
static inline void tick_nohz_restart_sched_tick(void) { }
-static inline void tick_nohz_update_jiffies(void) { }
static inline ktime_t tick_nohz_get_sleep_length(void)
{
ktime_t len = { .tv64 = NSEC_PER_SEC/HZ };
return len;
}
-static inline void tick_nohz_stop_idle(int cpu) { }
static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }
# endif /* !NO_HZ */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index c506f26..6ad6aec 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -254,16 +254,12 @@ asmlinkage void do_softirq(void)
*/
void irq_enter(void)
{
-#ifdef CONFIG_NO_HZ
int cpu = smp_processor_id();
- if (idle_cpu(cpu) && !in_interrupt())
- tick_nohz_stop_idle(cpu);
-#endif
- __irq_enter();
-#ifdef CONFIG_NO_HZ
+
if (idle_cpu(cpu))
- tick_nohz_update_jiffies();
-#endif
+ tick_check_idle(cpu);
+
+ __irq_enter();
}
#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index cb01cd8..f98a1b7 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -384,6 +384,19 @@ int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
}
/*
+ * Called from irq_enter() when idle was interrupted to reenable the
+ * per cpu device.
+ */
+void tick_check_oneshot_broadcast(int cpu)
+{
+ if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
+ struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
+
+ clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
+ }
+}
+
+/*
* Handle oneshot mode broadcasting
*/
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 4692487..b1c05bf 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -36,6 +36,7 @@ extern void tick_broadcast_switch_to_oneshot(void);
extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup);
extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
extern int tick_broadcast_oneshot_active(void);
+extern void tick_check_oneshot_broadcast(int cpu);
# else /* BROADCAST */
static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
@@ -45,6 +46,7 @@ static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
static inline void tick_broadcast_switch_to_oneshot(void) { }
static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
static inline int tick_broadcast_oneshot_active(void) { return 0; }
+static inline void tick_check_oneshot_broadcast(int cpu) { }
# endif /* !BROADCAST */
#else /* !ONESHOT */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a4d2193..d1b39e6 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -155,7 +155,7 @@ void tick_nohz_update_jiffies(void)
touch_softlockup_watchdog();
}
-void tick_nohz_stop_idle(int cpu)
+static void tick_nohz_stop_idle(int cpu)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
@@ -559,6 +559,20 @@ static inline void tick_nohz_switch_to_nohz(void) { }
#endif /* NO_HZ */
/*
+ * Called from irq_enter to notify about the possible interruption of idle()
+ */
+void tick_check_idle(int cpu)
+{
+#ifdef CONFIG_NO_HZ
+ if (!in_interrupt()) {
+ tick_nohz_stop_idle(cpu);
+ tick_nohz_update_jiffies();
+ }
+#endif
+ tick_check_oneshot_broadcast(cpu);
+}
+
+/*
* High resolution timer specific code
*/
#ifdef CONFIG_HIGH_RES_TIMERS