Update the usleep_range() function comment to make it clear that it can only be used in non-atomic context.
Previously we claimed usleep_range() was a drop-in replacement for udelay() where wakeup is flexible. But that's only true in non-atomic contexts, where it's possible to sleep instead of delay. Signed-off-by: Bjorn Helgaas <[email protected]> --- kernel/time/timer.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 3a95f97..c024c9f 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1702,9 +1702,15 @@ static void __sched do_usleep_range(unsigned long min, unsigned long max) } /** - * usleep_range - Drop in replacement for udelay where wakeup is flexible + * usleep_range - sleep for an approximate time * @min: Minimum time in usecs to sleep * @max: Maximum time in usecs to sleep + * + * In non-atomic context where the exact wakeup time is flexible, use + * usleep_range() instead of udelay(). The sleep improves responsiveness + * by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces + * power usage by allowing hrtimers to take advantage of an already- + * scheduled interrupt instead of scheduling a new one just for this sleep. */ void __sched usleep_range(unsigned long min, unsigned long max) {
