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Commit c569a23d authored by Nicholas Mc Guire's avatar Nicholas Mc Guire Committed by Thomas Gleixner
Browse files

time: Allow gcc to fold usecs_to_jiffies(constant) 



To allow constant folding in usecs_to_jiffies() conditionally calls
the HZ dependent _usecs_to_jiffies() helpers or, when gcc can not
figure out constant folding, __usecs_to_jiffies, which is the renamed
original usecs_to_jiffies() function.

Signed-off-by: default avatarNicholas Mc Guire <hofrat@osadl.org>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Joe Perches <joe@perches.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Andrew Hunter <ahh@google.com>
Cc: Paul Turner <pjt@google.com>
Cc: Michal Marek <mmarek@suse.cz>
Link: http://lkml.kernel.org/r/1432832996-12129-2-git-send-email-hofrat@osadl.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent ae60d6a0

include/linux/jiffies.h

+29 −1
Original line number Diff line number Diff line
@@ -383,10 +383,38 @@ static inline unsigned long _usecs_to_jiffies(const unsigned int u) 
}

#endif



/**

 * usecs_to_jiffies: - convert microseconds to jiffies

 * @u:	time in microseconds

 *

 * conversion is done as follows:

 *

 * - 'too large' values [that would result in larger than

 *   MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.

 *

 * - all other values are converted to jiffies by either multiplying

 *   the input value by a factor or dividing it with a factor and

 *   handling any 32-bit overflows as for msecs_to_jiffies.

 *

 * usecs_to_jiffies() checks for the passed in value being a constant

 * via __builtin_constant_p() allowing gcc to eliminate most of the

 * code, __usecs_to_jiffies() is called if the value passed does not

 * allow constant folding and the actual conversion must be done at

 * runtime.

 * the HZ range specific helpers _usecs_to_jiffies() are called both

 * directly here and from __msecs_to_jiffies() in the case where

 * constant folding is not possible.

 */

static inline unsigned long usecs_to_jiffies(const unsigned int u)

{

	if (__builtin_constant_p(u)) {

		if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))

			return MAX_JIFFY_OFFSET;

		return _usecs_to_jiffies(u);

	} else {

		return __usecs_to_jiffies(u);

	}

}



extern unsigned long timespec_to_jiffies(const struct timespec *value);

extern void jiffies_to_timespec(const unsigned long jiffies,