timers: Clarify usleep_range() function comment (b5227d03) · Commits · 戴 / test

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	Original line	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		* @min: Minimum time in usecs to sleep
	* @max: Maximum 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)		void __sched usleep_range(unsigned long min, unsigned long max)
	{		{

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