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Subject[patch 17/21] Switch itimers to hrtimer

- switch itimers to a hrtimers-based implementation

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

fs/exec.c | 6 +-
fs/proc/array.c | 6 +-
include/linux/sched.h | 5 +-
include/linux/timer.h | 2
kernel/exit.c | 2
kernel/fork.c | 6 +-
kernel/itimer.c | 108 ++++++++++++++++++++++++--------------------------
7 files changed, 66 insertions(+), 69 deletions(-)
Index: linux-2.6.15-rc5/fs/exec.c
===================================================================
--- linux-2.6.15-rc5.orig/fs/exec.c
+++ linux-2.6.15-rc5/fs/exec.c
@@ -632,10 +632,10 @@ static inline int de_thread(struct task_
* synchronize with any firing (by calling del_timer_sync)
* before we can safely let the old group leader die.
*/
- sig->real_timer.data = (unsigned long)current;
+ sig->real_timer.data = current;
spin_unlock_irq(lock);
- if (del_timer_sync(&sig->real_timer))
- add_timer(&sig->real_timer);
+ if (hrtimer_cancel(&sig->real_timer))
+ hrtimer_restart(&sig->real_timer);
spin_lock_irq(lock);
}
while (atomic_read(&sig->count) > count) {
Index: linux-2.6.15-rc5/fs/proc/array.c
===================================================================
--- linux-2.6.15-rc5.orig/fs/proc/array.c
+++ linux-2.6.15-rc5/fs/proc/array.c
@@ -330,7 +330,7 @@ static int do_task_stat(struct task_stru
unsigned long min_flt = 0, maj_flt = 0;
cputime_t cutime, cstime, utime, stime;
unsigned long rsslim = 0;
- unsigned long it_real_value = 0;
+ DEFINE_KTIME(it_real_value);
struct task_struct *t;
char tcomm[sizeof(task->comm)];

@@ -386,7 +386,7 @@ static int do_task_stat(struct task_stru
utime = cputime_add(utime, task->signal->utime);
stime = cputime_add(stime, task->signal->stime);
}
- it_real_value = task->signal->it_real_value;
+ it_real_value = task->signal->real_timer.expires;
}
ppid = pid_alive(task) ? task->group_leader->real_parent->tgid : 0;
read_unlock(&tasklist_lock);
@@ -435,7 +435,7 @@ static int do_task_stat(struct task_stru
priority,
nice,
num_threads,
- jiffies_to_clock_t(it_real_value),
+ (long) ktime_to_clock_t(it_real_value),
start_time,
vsize,
mm ? get_mm_rss(mm) : 0,
Index: linux-2.6.15-rc5/include/linux/sched.h
===================================================================
--- linux-2.6.15-rc5.orig/include/linux/sched.h
+++ linux-2.6.15-rc5/include/linux/sched.h
@@ -104,6 +104,7 @@ extern unsigned long nr_iowait(void);
#include <linux/param.h>
#include <linux/resource.h>
#include <linux/timer.h>
+#include <linux/hrtimer.h>

#include <asm/processor.h>

@@ -402,8 +403,8 @@ struct signal_struct {
struct list_head posix_timers;

/* ITIMER_REAL timer for the process */
- struct timer_list real_timer;
- unsigned long it_real_value, it_real_incr;
+ struct hrtimer real_timer;
+ ktime_t it_real_incr;

/* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
cputime_t it_prof_expires, it_virt_expires;
Index: linux-2.6.15-rc5/include/linux/timer.h
===================================================================
--- linux-2.6.15-rc5.orig/include/linux/timer.h
+++ linux-2.6.15-rc5/include/linux/timer.h
@@ -96,6 +96,6 @@ static inline void add_timer(struct time

extern void init_timers(void);
extern void run_local_timers(void);
-extern void it_real_fn(unsigned long);
+extern int it_real_fn(void *);

#endif
Index: linux-2.6.15-rc5/kernel/exit.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/exit.c
+++ linux-2.6.15-rc5/kernel/exit.c
@@ -842,7 +842,7 @@ fastcall NORET_TYPE void do_exit(long co
}
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
- del_timer_sync(&tsk->signal->real_timer);
+ hrtimer_cancel(&tsk->signal->real_timer);
exit_itimers(tsk->signal);
acct_process(code);
}
Index: linux-2.6.15-rc5/kernel/fork.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/fork.c
+++ linux-2.6.15-rc5/kernel/fork.c
@@ -793,10 +793,10 @@ static inline int copy_signal(unsigned l
init_sigpending(&sig->shared_pending);
INIT_LIST_HEAD(&sig->posix_timers);

- sig->it_real_value = sig->it_real_incr = 0;
+ hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC);
+ sig->it_real_incr.tv64 = 0;
sig->real_timer.function = it_real_fn;
- sig->real_timer.data = (unsigned long) tsk;
- init_timer(&sig->real_timer);
+ sig->real_timer.data = tsk;

sig->it_virt_expires = cputime_zero;
sig->it_virt_incr = cputime_zero;
Index: linux-2.6.15-rc5/kernel/itimer.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/itimer.c
+++ linux-2.6.15-rc5/kernel/itimer.c
@@ -12,36 +12,46 @@
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/posix-timers.h>
+#include <linux/hrtimer.h>

#include <asm/uaccess.h>

-static unsigned long it_real_value(struct signal_struct *sig)
+/**
+ * itimer_get_remtime - get remaining time for the timer
+ *
+ * @timer: the timer to read
+ *
+ * Returns the delta between the expiry time and now, which can be
+ * less than zero or 1usec for an pending expired timer
+ */
+static struct timeval itimer_get_remtime(struct hrtimer *timer)
{
- unsigned long val = 0;
- if (timer_pending(&sig->real_timer)) {
- val = sig->real_timer.expires - jiffies;
-
- /* look out for negative/zero itimer.. */
- if ((long) val <= 0)
- val = 1;
- }
- return val;
+ ktime_t rem = hrtimer_get_remaining(timer);
+
+ /*
+ * Racy but safe: if the itimer expires after the above
+ * hrtimer_get_remtime() call but before this condition
+ * then we return 0 - which is correct.
+ */
+ if (hrtimer_active(timer)) {
+ if (rem.tv64 <= 0)
+ rem.tv64 = NSEC_PER_USEC;
+ } else
+ rem.tv64 = 0;
+
+ return ktime_to_timeval(rem);
}

int do_getitimer(int which, struct itimerval *value)
{
struct task_struct *tsk = current;
- unsigned long interval, val;
cputime_t cinterval, cval;

switch (which) {
case ITIMER_REAL:
- spin_lock_irq(&tsk->sighand->siglock);
- interval = tsk->signal->it_real_incr;
- val = it_real_value(tsk->signal);
- spin_unlock_irq(&tsk->sighand->siglock);
- jiffies_to_timeval(val, &value->it_value);
- jiffies_to_timeval(interval, &value->it_interval);
+ value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
+ value->it_interval =
+ ktime_to_timeval(tsk->signal->it_real_incr);
break;
case ITIMER_VIRTUAL:
read_lock(&tasklist_lock);
@@ -113,59 +123,45 @@ asmlinkage long sys_getitimer(int which,
}


-void it_real_fn(unsigned long __data)
+/*
+ * The timer is automagically restarted, when interval != 0
+ */
+int it_real_fn(void *data)
{
- struct task_struct * p = (struct task_struct *) __data;
- unsigned long inc = p->signal->it_real_incr;
+ struct task_struct *tsk = (struct task_struct *) data;

- send_group_sig_info(SIGALRM, SEND_SIG_PRIV, p);
+ send_group_sig_info(SIGALRM, SEND_SIG_PRIV, tsk);

- /*
- * Now restart the timer if necessary. We don't need any locking
- * here because do_setitimer makes sure we have finished running
- * before it touches anything.
- * Note, we KNOW we are (or should be) at a jiffie edge here so
- * we don't need the +1 stuff. Also, we want to use the prior
- * expire value so as to not "slip" a jiffie if we are late.
- * Deal with requesting a time prior to "now" here rather than
- * in add_timer.
- */
- if (!inc)
- return;
- while (time_before_eq(p->signal->real_timer.expires, jiffies))
- p->signal->real_timer.expires += inc;
- add_timer(&p->signal->real_timer);
+ if (tsk->signal->it_real_incr.tv64 != 0) {
+ hrtimer_forward(&tsk->signal->real_timer,
+ tsk->signal->it_real_incr);
+
+ return HRTIMER_RESTART;
+ }
+ return HRTIMER_NORESTART;
}

int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
{
struct task_struct *tsk = current;
- unsigned long val, interval, expires;
+ struct hrtimer *timer;
+ ktime_t expires;
cputime_t cval, cinterval, nval, ninterval;

switch (which) {
case ITIMER_REAL:
-again:
- spin_lock_irq(&tsk->sighand->siglock);
- interval = tsk->signal->it_real_incr;
- val = it_real_value(tsk->signal);
- /* We are sharing ->siglock with it_real_fn() */
- if (try_to_del_timer_sync(&tsk->signal->real_timer) < 0) {
- spin_unlock_irq(&tsk->sighand->siglock);
- goto again;
- }
- tsk->signal->it_real_incr =
- timeval_to_jiffies(&value->it_interval);
- expires = timeval_to_jiffies(&value->it_value);
- if (expires)
- mod_timer(&tsk->signal->real_timer,
- jiffies + 1 + expires);
- spin_unlock_irq(&tsk->sighand->siglock);
+ timer = &tsk->signal->real_timer;
+ hrtimer_cancel(timer);
if (ovalue) {
- jiffies_to_timeval(val, &ovalue->it_value);
- jiffies_to_timeval(interval,
- &ovalue->it_interval);
+ ovalue->it_value = itimer_get_remtime(timer);
+ ovalue->it_interval
+ = ktime_to_timeval(tsk->signal->it_real_incr);
}
+ tsk->signal->it_real_incr =
+ timeval_to_ktime(value->it_interval);
+ expires = timeval_to_ktime(value->it_value);
+ if (expires.tv64 != 0)
+ hrtimer_start(timer, expires, HRTIMER_REL);
break;
case ITIMER_VIRTUAL:
nval = timeval_to_cputime(&value->it_value);
--

-
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