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convert a few do_div users

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This converts a few users of do_div to div_[su]64 and this demonstrates nicely
how it can reduce some expressions to one-liners.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roman Zippel 2008-05-01 04:34:26 -07:00 • committed by Linus Torvalds
parent 2418f4f28f
commit 71abb3af62
2 changed files with 15 additions and 39 deletions
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29
kernel/time.c
View file

@ -36,6 +36,7 @@
#include <linux/security.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/math64.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@ -587,9 +588,7 @@ clock_t jiffies_to_clock_t(long x)
return x / (HZ / USER_HZ);
# endif
#else
u64 tmp = (u64)x * TICK_NSEC;
do_div(tmp, (NSEC_PER_SEC / USER_HZ));
return (long)tmp;
return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
#endif
}
EXPORT_SYMBOL(jiffies_to_clock_t);
@ -601,16 +600,12 @@ unsigned long clock_t_to_jiffies(unsigned long x)
return ~0UL;
return x * (HZ / USER_HZ);
#else
u64 jif;
/* Don't worry about loss of precision here .. */
if (x >= ~0UL / HZ * USER_HZ)
return ~0UL;
/* .. but do try to contain it here */
jif = x * (u64) HZ;
do_div(jif, USER_HZ);
return jif;
return div_u64((u64)x * HZ, USER_HZ);
#endif
}
EXPORT_SYMBOL(clock_t_to_jiffies);
@ -619,10 +614,9 @@ u64 jiffies_64_to_clock_t(u64 x)
{
#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0
# if HZ < USER_HZ
x *= USER_HZ;
do_div(x, HZ);
x = div_u64(x * USER_HZ, HZ);
# elif HZ > USER_HZ
do_div(x, HZ / USER_HZ);
x = div_u64(x, HZ / USER_HZ);
# else
/* Nothing to do */
# endif
@ -632,8 +626,7 @@ u64 jiffies_64_to_clock_t(u64 x)
* but even this doesn't overflow in hundreds of years
* in 64 bits, so..
*/
x *= TICK_NSEC;
do_div(x, (NSEC_PER_SEC / USER_HZ));
x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ));
#endif
return x;
}
@ -642,21 +635,17 @@ EXPORT_SYMBOL(jiffies_64_to_clock_t);
u64 nsec_to_clock_t(u64 x)
{
#if (NSEC_PER_SEC % USER_HZ) == 0
do_div(x, (NSEC_PER_SEC / USER_HZ));
return div_u64(x, NSEC_PER_SEC / USER_HZ);
#elif (USER_HZ % 512) == 0
x *= USER_HZ/512;
do_div(x, (NSEC_PER_SEC / 512));
return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512);
#else
/*
* max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
* overflow after 64.99 years.
* exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
*/
x *= 9;
do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) /
USER_HZ));
return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ);
#endif
return x;
}
#if (BITS_PER_LONG < 64)