clockevents: Prevent oneshot mode when broadcast device is periodic

commit 3a142a0672b48a853f00af61f184c7341ac9c99d upstream.

When the per cpu timer is marked CLOCK_EVT_FEAT_C3STOP, then we only
can switch into oneshot mode, when the backup broadcast device
supports oneshot mode as well. Otherwise we would try to switch the
broadcast device into an unsupported mode unconditionally. This went
unnoticed so far as the current available broadcast devices support
oneshot mode. Seth unearthed this problem while debugging and working
around an hpet related BIOS wreckage.

Add the necessary check to tick_is_oneshot_available().

Reported-and-tested-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <alpine.LFD.2.00.1102252231200.2701@localhost6.localdomain6>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index c2ec25087a35a0cbf265258caf953d83424314f9..49446b1c68c20df641542c4956506d88c40a1081 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -600,4 +600,14 @@ int tick_broadcast_oneshot_active(void)
        return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 }
 
+/*
+ * Check whether the broadcast device supports oneshot.
+ */
+bool tick_broadcast_oneshot_available(void)
+{
+       struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+       return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
+}
+
 #endif

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 83c4417b6a3cccd734c8f7f9386670641babd0c8..a943826402b8567f4fc15e1c36a8a7326e3b67d7 100644 (file)
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -51,7 +51,11 @@ int tick_is_oneshot_available(void)
 {
        struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
 
-       return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
+       if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
+               return 0;
+       if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
+               return 1;
+       return tick_broadcast_oneshot_available();
 }
 
 /*

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index b1c05bf75ee0ce36e0664d3e2e71d00ac0e09edd..32fbf20ae2d632cf4f4df942e01a585ebf30504e 100644 (file)
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -37,6 +37,7 @@ 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);
+bool tick_broadcast_oneshot_available(void);
 # else /* BROADCAST */
 static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 {
@@ -47,6 +48,7 @@ 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) { }
+static inline bool tick_broadcast_oneshot_available(void) { return true; }
 # endif /* !BROADCAST */
 
 #else /* !ONESHOT */
@@ -77,6 +79,7 @@ static inline int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
        return 0;
 }
 static inline int tick_broadcast_oneshot_active(void) { return 0; }
+static inline bool tick_broadcast_oneshot_available(void) { return false; }
 #endif /* !TICK_ONESHOT */
 
 /*