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alarmtimers: Change alarmtimer functions to return alarmtimer_restart values

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In order to properly fix the denial of service issue with high freq
periodic alarm timers, we need to push the re-arming logic into the
alarm timer handler, much as the hrtimer code does.

This patch introduces alarmtimer_restart enum and changes the
alarmtimer handler declarations to use it as a return value. Further,
to ease following changes, it extends the alarmtimer handler functions
to also take the time at expiration. No logic is yet modified.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
John Stultz 2011-08-10 10:37:59 -07:00
parent 6af7e471e5
commit 4b41308d2d
2 changed files with 16 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/alarmtimer.h
View File

@ -13,6 +13,11 @@ enum alarmtimer_type {
ALARM_NUMTYPE,
};
enum alarmtimer_restart {
ALARMTIMER_NORESTART,
ALARMTIMER_RESTART,
};
/**
* struct alarm - Alarm timer structure
* @node: timerqueue node for adding to the event list this value
@ -26,14 +31,14 @@ enum alarmtimer_type {
struct alarm {
struct timerqueue_node node;
ktime_t period;
void (*function)(struct alarm *);
enum alarmtimer_restart (*function)(struct alarm *, ktime_t now);
enum alarmtimer_type type;
bool enabled;
void *data;
};
void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
void (*function)(struct alarm *));
enum alarmtimer_restart (*function)(struct alarm *, ktime_t));
void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period);
void alarm_cancel(struct alarm *alarm);

13
kernel/time/alarmtimer.c
View File

@ -196,7 +196,7 @@ static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
}
spin_unlock_irqrestore(&base->lock, flags);
if (alarm->function)
alarm->function(alarm);
alarm->function(alarm, now);
spin_lock_irqsave(&base->lock, flags);
}
@ -299,7 +299,7 @@ static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
* @function: callback that is run when the alarm fires
*/
void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
void (*function)(struct alarm *))
enum alarmtimer_restart (*function)(struct alarm *, ktime_t))
{
timerqueue_init(&alarm->node);
alarm->period = ktime_set(0, 0);
@ -365,12 +365,15 @@ static enum alarmtimer_type clock2alarm(clockid_t clockid)
*
* Posix timer callback for expired alarm timers.
*/
static void alarm_handle_timer(struct alarm *alarm)
static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,
ktime_t now)
{
struct k_itimer *ptr = container_of(alarm, struct k_itimer,
it.alarmtimer);
if (posix_timer_event(ptr, 0) != 0)
ptr->it_overrun++;
return ALARMTIMER_NORESTART;
}
/**
@ -509,13 +512,15 @@ static int alarm_timer_set(struct k_itimer *timr, int flags,
*
* Wakes up the task that set the alarmtimer
*/
static void alarmtimer_nsleep_wakeup(struct alarm *alarm)
static enum alarmtimer_restart alarmtimer_nsleep_wakeup(struct alarm *alarm,
ktime_t now)
{
struct task_struct *task = (struct task_struct *)alarm->data;
alarm->data = NULL;
if (task)
wake_up_process(task);
return ALARMTIMER_NORESTART;
}
/**