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Subject[PATCH 1/4] timer: generalize timer->base flags handling
Date
To prepare for addition of another flag, generalize timer->base flags
handling.

* Rename from TBASE_*_FLAG to TIMER_* and make them LU constants.

* Define and use TIMER_FLAG_MASK for flags masking so that multiple
flags can be handled correctly.

* Don't dereference timer->base directly even if
!tbase_get_deferrable(). All two such places are already passed in
@base, so use it instead.

* Make sure tvec_base's alignment is large enough for timer->base
flags using BUILD_BUG_ON().

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/timer.h | 6 ++++--
kernel/timer.c | 21 +++++++++++++--------
2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/include/linux/timer.h b/include/linux/timer.h
index 6abd913..cbd32ec 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -58,7 +58,9 @@ extern struct tvec_base boot_tvec_bases;
* the timer will be serviced when the CPU eventually wakes up with a
* subsequent non-deferrable timer.
*/
-#define TBASE_DEFERRABLE_FLAG (0x1)
+#define TIMER_DEFERRABLE 0x1LU
+
+#define TIMER_FLAG_MASK 0x1LU

#define TIMER_INITIALIZER(_function, _expires, _data) { \
.entry = { .prev = TIMER_ENTRY_STATIC }, \
@@ -72,7 +74,7 @@ extern struct tvec_base boot_tvec_bases;
}

#define TBASE_MAKE_DEFERRED(ptr) ((struct tvec_base *) \
- ((unsigned char *)(ptr) + TBASE_DEFERRABLE_FLAG))
+ ((unsigned char *)(ptr) + TIMER_DEFERRABLE))

#define TIMER_DEFERRED_INITIALIZER(_function, _expires, _data) {\
.entry = { .prev = TIMER_ENTRY_STATIC }, \
diff --git a/kernel/timer.c b/kernel/timer.c
index a61c093..cf7af56 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -92,12 +92,12 @@ static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
/* Functions below help us manage 'deferrable' flag */
static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
{
- return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
+ return ((unsigned int)(unsigned long)base & TIMER_DEFERRABLE);
}

static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
{
- return ((struct tvec_base *)((unsigned long)base & ~TBASE_DEFERRABLE_FLAG));
+ return ((struct tvec_base *)((unsigned long)base & ~TIMER_FLAG_MASK));
}

static inline void timer_set_deferrable(struct timer_list *timer)
@@ -108,8 +108,9 @@ static inline void timer_set_deferrable(struct timer_list *timer)
static inline void
timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
{
- timer->base = (struct tvec_base *)((unsigned long)(new_base) |
- tbase_get_deferrable(timer->base));
+ unsigned long flags = (unsigned long)timer->base & TIMER_FLAG_MASK;
+
+ timer->base = (struct tvec_base *)((unsigned long)(new_base) | flags);
}

static unsigned long round_jiffies_common(unsigned long j, int cpu,
@@ -686,7 +687,7 @@ detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
{
detach_timer(timer, true);
if (!tbase_get_deferrable(timer->base))
- timer->base->active_timers--;
+ base->active_timers--;
}

static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
@@ -697,7 +698,7 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,

detach_timer(timer, clear_pending);
if (!tbase_get_deferrable(timer->base)) {
- timer->base->active_timers--;
+ base->active_timers--;
if (timer->expires == base->next_timer)
base->next_timer = base->timer_jiffies;
}
@@ -1800,9 +1801,13 @@ static struct notifier_block __cpuinitdata timers_nb = {

void __init init_timers(void)
{
- int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
- (void *)(long)smp_processor_id());
+ int err;
+
+ /* ensure there are enough low bits for flags in timer->base pointer */
+ BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);

+ err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
+ (void *)(long)smp_processor_id());
init_timer_stats();

BUG_ON(err != NOTIFY_OK);
--
1.7.7.3


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