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Subject[RFC PATCH 5/6] cpu-timers: change arm_timer() locking
Date
Spread p->sighand->siglock locking scope to assure signal->cputimer
is always running when we are setuping signal->cputime_expires.

This further assure we do not iterate over all threads in
fastpath_timer_check() when calling thread_group_cputimer().

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
---
kernel/posix-cpu-timers.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 08506ff..68d4045 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -549,7 +549,7 @@ static inline int expires_gt(cputime_t expires, cputime_t new_exp)
/*
* Insert the timer on the appropriate list before any timers that
* expire later. This must be called with the tasklist_lock held
- * for reading, and interrupts disabled.
+ * for reading, interrupts disabled and p->sighand->siglock taken.
*/
static void arm_timer(struct k_itimer *timer)
{
@@ -568,9 +568,6 @@ static void arm_timer(struct k_itimer *timer)
}
head += CPUCLOCK_WHICH(timer->it_clock);

- BUG_ON(!irqs_disabled());
- spin_lock(&p->sighand->siglock);
-
listpos = head;
list_for_each_entry(next, head, entry) {
if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
@@ -605,8 +602,6 @@ static void arm_timer(struct k_itimer *timer)
break;
}
}
-
- spin_unlock(&p->sighand->siglock);
}

/*
@@ -719,7 +714,6 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
ret = TIMER_RETRY;
} else
list_del_init(&timer->it.cpu.entry);
- spin_unlock(&p->sighand->siglock);

/*
* We need to sample the current value to convert the new
@@ -773,6 +767,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
* disable this firing since we are already reporting
* it as an overrun (thanks to bump_cpu_timer above).
*/
+ spin_unlock(&p->sighand->siglock);
read_unlock(&tasklist_lock);
goto out;
}
@@ -792,6 +787,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
arm_timer(timer);
}

+ spin_unlock(&p->sighand->siglock);
read_unlock(&tasklist_lock);

/*
@@ -1201,6 +1197,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
goto out;
}
read_lock(&tasklist_lock); /* arm_timer needs it. */
+ spin_lock(&p->sighand->siglock);
} else {
read_lock(&tasklist_lock);
if (unlikely(p->signal == NULL)) {
@@ -1221,6 +1218,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
clear_dead_task(timer, now);
goto out_unlock;
}
+ spin_lock(&p->sighand->siglock);
cpu_timer_sample_group(timer->it_clock, p, &now);
bump_cpu_timer(timer, now);
/* Leave the tasklist_lock locked for the call below. */
@@ -1229,7 +1227,9 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
/*
* Now re-arm for the new expiry time.
*/
+ BUG_ON(!irqs_disabled());
arm_timer(timer);
+ spin_unlock(&p->sighand->siglock);

out_unlock:
read_unlock(&tasklist_lock);
--
1.6.2.5


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