@@ -1742,15 +1742,19 @@ schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
- * pass before the routine returns.
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process()).
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
- * delivered to the current task.
+ * delivered to the current task or the current task is explicitly woken
+ * up.
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
*
- * Returns 0 when the timer has expired otherwise -EINTR
+ * Returns 0 when the timer has expired. If the task was woken before the
+ * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
+ * by an explicit wakeup, it returns -EINTR.
*/
int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
const enum hrtimer_mode mode)
@@ -1772,15 +1776,19 @@ EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
- * pass before the routine returns.
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process()).
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
- * delivered to the current task.
+ * delivered to the current task or the current task is explicitly woken
+ * up.
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
*
- * Returns 0 when the timer has expired otherwise -EINTR
+ * Returns 0 when the timer has expired. If the task was woken before the
+ * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
+ * by an explicit wakeup, it returns -EINTR.
*/
int __sched schedule_hrtimeout(ktime_t *expires,
const enum hrtimer_mode mode)
@@ -1691,11 +1691,12 @@ static void process_timeout(unsigned long __data)
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
- * pass before the routine returns. The routine will return 0
+ * pass before the routine returns unless the current task is explicitly
+ * woken up, (e.g. by wake_up_process())".
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
- * delivered to the current task. In this case the remaining time
- * in jiffies will be returned, or 0 if the timer expired in time
+ * delivered to the current task or the current task is explicitly woken
+ * up.
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
@@ -1704,7 +1705,9 @@ static void process_timeout(unsigned long __data)
* the CPU away without a bound on the timeout. In this case the return
* value will be %MAX_SCHEDULE_TIMEOUT.
*
- * In all cases the return value is guaranteed to be non-negative.
+ * Returns 0 when the timer has expired otherwise the remaining time in
+ * jiffies will be returned. In all cases the return value is guaranteed
+ * to be non-negative.
*/
signed long __sched schedule_timeout(signed long timeout)
{
The documentatoin for schedule_timeout(), schedule_hrtimeout(), and schedule_hrtimeout_range() all claimed that the routines couldn't possibly return early if the task state was TASK_UNINTERRUPTIBLE. This was simply not true since anyone calling wake_up_process() would cause those routines to exit early. As some evidence that the documentation was broken (not the code): - If we changed the code to match the documentation, msleep() would be identical to schedule_timeout_uninterruptible() and msleep_interruptible() would be identical to schedule_timeout_interruptible(). That doesn't seem likely to have been the intention. - The schedule() function sleeps until a task is woken up. Logically, one would expect that the schedule_timeout() function would sleep until a task is woken up or a timeout occurrs. As part of the above observation, it can be seen that schedule_hrtimeout() and schedule_hrtimeout_range() might return -EINTR even if the task state was TASK_UNINTERRUPTIBLE. This isn't terrible behavior so we'll document it and keep it as-is. After all, trying to match schedule_timeout() and return the time left would incure a bunch of extra calculation cost that isn't needed in all cases. Suggested-by: Daniel Kurtz <djkurtz@chromium.org> Signed-off-by: Douglas Anderson <dianders@chromium.org> --- Changes in v4: - Fixed stray double quotes. - Updated wording as per Thomas Gleixner. Changes in v3: - Documentation fix new for v3. kernel/time/hrtimer.c | 20 ++++++++++++++------ kernel/time/timer.c | 11 +++++++---- 2 files changed, 21 insertions(+), 10 deletions(-)