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authorThomas Gleixner <tglx@linutronix.de>2007-02-16 01:27:51 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-16 08:13:58 -0800
commit303e967ff90a9d19ad3f8c9028ccbfa7f408fbb3 (patch)
treecd8c057e98b57896ffbbe4d98a4264393a652204 /include
parent3c8aa39d7c445ae2612b6b626f76f077e7a7ab0d (diff)
[PATCH] hrtimers; add state tracking
Reintroduce ktimers feature "optimized away" by the ktimers review process: multiple hrtimer states to enable the running of hrtimers without holding the cpu-base-lock. (The "optimized" rbtree hack carried only 2 states worth of information and we need 4 for high resolution timers and dynamic ticks.) No functional changes. Build-fixes-from: Andrew Morton <akpm@osdl.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Roman Zippel <zippel@linux-m68k.org> Cc: john stultz <johnstul@us.ibm.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/hrtimer.h36
1 files changed, 35 insertions, 1 deletions
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index e00fc4d3d74f..d8cdac2d28d6 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -40,6 +40,34 @@ enum hrtimer_restart {
HRTIMER_RESTART, /* Timer must be restarted */
};
+/*
+ * Bit values to track state of the timer
+ *
+ * Possible states:
+ *
+ * 0x00 inactive
+ * 0x01 enqueued into rbtree
+ * 0x02 callback function running
+ * 0x03 callback function running and enqueued
+ * (was requeued on another CPU)
+ *
+ * The "callback function running and enqueued" status is only possible on
+ * SMP. It happens for example when a posix timer expired and the callback
+ * queued a signal. Between dropping the lock which protects the posix timer
+ * and reacquiring the base lock of the hrtimer, another CPU can deliver the
+ * signal and rearm the timer. We have to preserve the callback running state,
+ * as otherwise the timer could be removed before the softirq code finishes the
+ * the handling of the timer.
+ *
+ * The HRTIMER_STATE_ENQUEUE bit is always or'ed to the current state to
+ * preserve the HRTIMER_STATE_CALLBACK bit in the above scenario.
+ *
+ * All state transitions are protected by cpu_base->lock.
+ */
+#define HRTIMER_STATE_INACTIVE 0x00
+#define HRTIMER_STATE_ENQUEUED 0x01
+#define HRTIMER_STATE_CALLBACK 0x02
+
/**
* struct hrtimer - the basic hrtimer structure
* @node: red black tree node for time ordered insertion
@@ -48,6 +76,7 @@ enum hrtimer_restart {
* which the timer is based.
* @function: timer expiry callback function
* @base: pointer to the timer base (per cpu and per clock)
+ * @state: state information (See bit values above)
*
* The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
*/
@@ -56,6 +85,7 @@ struct hrtimer {
ktime_t expires;
enum hrtimer_restart (*function)(struct hrtimer *);
struct hrtimer_clock_base *base;
+ unsigned long state;
};
/**
@@ -141,9 +171,13 @@ extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);
extern ktime_t hrtimer_get_next_event(void);
#endif
+/*
+ * A timer is active, when it is enqueued into the rbtree or the callback
+ * function is running.
+ */
static inline int hrtimer_active(const struct hrtimer *timer)
{
- return rb_parent(&timer->node) != &timer->node;
+ return timer->state != HRTIMER_STATE_INACTIVE;
}
/* Forward a hrtimer so it expires after now: */