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| author | Bjorn Helgaas <bhelgaas@google.com> | 2016-05-31 16:23:02 -0500 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-06-10 00:59:14 +0200 |
| commit | b5227d03b7191a9a44bf75a4c228a6a9ddbe781b (patch) | |
| tree | c9598d40a1161ddaf9afef234f8c6c2c4bc5dcaa /kernel/time/timer.c | |
| parent | 2895a5e5b3ae78d9923a91fce405d4a2f32c4309 (diff) | |
timers: Clarify usleep_range() function comment
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 <bhelgaas@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20160531212302.28502.44995.stgit@bhelgaas-glaptop2.roam.corp.google.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/timer.c')
| -rw-r--r-- | kernel/time/timer.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 3a95f9728778..67dd6103003a 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) { |