timers: Clarify usleep_range() function comment (b5227d03) · Commits · e / devices / android_kernel_teracube_emerald

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>

kernel/time/timer.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -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)
		{