Revision 2b369478e1856e3809f439495567474725931585 authored by Linus Torvalds on 09 February 2017, 20:25:42 UTC, committed by Linus Torvalds on 09 February 2017, 20:25:42 UTC
Pull pstore fix from Kees Cook: "Fix pstore regression (boot Oops) when ftrace disabled, from Brian Norris" * tag 'pstore-v4.10-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: pstore: don't OOPS when there are no ftrace zones
gcd.c
#include <linux/kernel.h>
#include <linux/gcd.h>
#include <linux/export.h>
/*
* This implements the binary GCD algorithm. (Often attributed to Stein,
* but as Knuth has noted, appears in a first-century Chinese math text.)
*
* This is faster than the division-based algorithm even on x86, which
* has decent hardware division.
*/
#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) && !defined(CPU_NO_EFFICIENT_FFS)
/* If __ffs is available, the even/odd algorithm benchmarks slower. */
unsigned long gcd(unsigned long a, unsigned long b)
{
unsigned long r = a | b;
if (!a || !b)
return r;
b >>= __ffs(b);
if (b == 1)
return r & -r;
for (;;) {
a >>= __ffs(a);
if (a == 1)
return r & -r;
if (a == b)
return a << __ffs(r);
if (a < b)
swap(a, b);
a -= b;
}
}
#else
/* If normalization is done by loops, the even/odd algorithm is a win. */
unsigned long gcd(unsigned long a, unsigned long b)
{
unsigned long r = a | b;
if (!a || !b)
return r;
/* Isolate lsbit of r */
r &= -r;
while (!(b & r))
b >>= 1;
if (b == r)
return r;
for (;;) {
while (!(a & r))
a >>= 1;
if (a == r)
return r;
if (a == b)
return a;
if (a < b)
swap(a, b);
a -= b;
a >>= 1;
if (a & r)
a += b;
a >>= 1;
}
}
#endif
EXPORT_SYMBOL_GPL(gcd);
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