[RFC PATCH RT 2/2] time/hrtimer: Embed hrtimer mode into hrtimer_sleeper

Juri Lelli
2019-02-14T13:37:51Z

Changes to hrtimer mode (potentially made by __hrtimer_init_sleeper() on
PREEMPT_RT_FULL are not visible to do_nanosleep(), and thus not
accounted for by hrtimer_start_expires() call path.

Embed hrtimer mode into hrtimer_sleeper struct, so that the same mode is
used by code following hrtimer_sleeper initialization.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
---
include/linux/hrtimer.h | 2 ++
kernel/time/hrtimer.c | 11 ++++++-----
2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index c6d4941c7dd8..d5f11ef5330a 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -130,12 +130,14 @@ struct hrtimer {
* struct hrtimer_sleeper - simple sleeper structure
* @timer: embedded timer structure
* @task: task to wake up
+ * @mode: hrtimer mode
*
* task is set to NULL, when the timer expires.
*/
struct hrtimer_sleeper {
struct hrtimer timer;
struct task_struct *task;
+ enum hrtimer_mode mode;
};

#ifdef CONFIG_64BIT
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 4a905fb721a1..5067aba434fe 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1725,6 +1725,7 @@ static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
__hrtimer_init(&sl->timer, clock_id, mode);
sl->timer.function = hrtimer_wakeup;
sl->task = task;
+ sl->mode = mode;
}

/**
@@ -1774,20 +1775,20 @@ int nanosleep_copyout(struct restart_block *restart, struct timespec64 *ts)
return -ERESTART_RESTARTBLOCK;
}

-static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
+static int __sched do_nanosleep(struct hrtimer_sleeper *t)
{
struct restart_block *restart;

do {
set_current_state(TASK_INTERRUPTIBLE);
- hrtimer_start_expires(&t->timer, mode);
+ hrtimer_start_expires(&t->timer, t->mode);

if (likely(t->task))
freezable_schedule();

__set_current_state(TASK_RUNNING);
hrtimer_cancel(&t->timer);
- mode = HRTIMER_MODE_ABS;
+ t->mode = HRTIMER_MODE_ABS;

} while (t->task && !signal_pending(current));

@@ -1817,7 +1818,7 @@ static long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
hrtimer_init_sleeper_on_stack(&t, restart->nanosleep.clockid,
HRTIMER_MODE_ABS, current);
hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
- ret = do_nanosleep(&t, HRTIMER_MODE_ABS);
+ ret = do_nanosleep(&t);
destroy_hrtimer_on_stack(&t.timer);
return ret;
}
@@ -1836,7 +1837,7 @@ long hrtimer_nanosleep(const struct timespec64 *rqtp,

hrtimer_init_sleeper_on_stack(&t, clockid, mode, current);
hrtimer_set_expires_range_ns(&t.timer, timespec64_to_ktime(*rqtp), slack);
- ret = do_nanosleep(&t, mode);
+ ret = do_nanosleep(&t);
if (ret != -ERESTART_RESTARTBLOCK)
goto out;

--
2.17.2