Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched_clock: Fix atomicity/continuity bug by using cmpxchg64()
  x86: Provide an alternative() based cmpxchg64()
This commit is contained in:
Linus Torvalds 2009-09-30 15:10:40 -07:00
commit 84d88d5d4e
5 changed files with 85 additions and 16 deletions

View file

@ -312,19 +312,23 @@ static inline unsigned long cmpxchg_386(volatile void *ptr, unsigned long old,
extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);
#define cmpxchg64(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \
if (likely(boot_cpu_data.x86 > 4)) \
__ret = (__typeof__(*(ptr)))__cmpxchg64((ptr), \
(unsigned long long)(o), \
(unsigned long long)(n)); \
else \
__ret = (__typeof__(*(ptr)))cmpxchg_486_u64((ptr), \
(unsigned long long)(o), \
(unsigned long long)(n)); \
__ret; \
})
#define cmpxchg64(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \
__typeof__(*(ptr)) __old = (o); \
__typeof__(*(ptr)) __new = (n); \
alternative_io("call cmpxchg8b_emu", \
"lock; cmpxchg8b (%%esi)" , \
X86_FEATURE_CX8, \
"=A" (__ret), \
"S" ((ptr)), "0" (__old), \
"b" ((unsigned int)__new), \
"c" ((unsigned int)(__new>>32)) \
: "memory"); \
__ret; })
#define cmpxchg64_local(ptr, o, n) \
({ \
__typeof__(*(ptr)) __ret; \

View file

@ -10,6 +10,14 @@
EXPORT_SYMBOL(mcount);
#endif
/*
* Note, this is a prototype to get at the symbol for
* the export, but dont use it from C code, it is used
* by assembly code and is not using C calling convention!
*/
extern void cmpxchg8b_emu(void);
EXPORT_SYMBOL(cmpxchg8b_emu);
/* Networking helper routines. */
EXPORT_SYMBOL(csum_partial_copy_generic);

View file

@ -15,7 +15,7 @@ ifeq ($(CONFIG_X86_32),y)
obj-y += atomic64_32.o
lib-y += checksum_32.o
lib-y += strstr_32.o
lib-y += semaphore_32.o string_32.o
lib-y += semaphore_32.o string_32.o cmpxchg8b_emu.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
else

View file

@ -0,0 +1,57 @@
/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; version 2
* of the License.
*
*/
#include <linux/linkage.h>
#include <asm/alternative-asm.h>
#include <asm/frame.h>
#include <asm/dwarf2.h>
.text
/*
* Inputs:
* %esi : memory location to compare
* %eax : low 32 bits of old value
* %edx : high 32 bits of old value
* %ebx : low 32 bits of new value
* %ecx : high 32 bits of new value
*/
ENTRY(cmpxchg8b_emu)
CFI_STARTPROC
#
# Emulate 'cmpxchg8b (%esi)' on UP except we don't
# set the whole ZF thing (caller will just compare
# eax:edx with the expected value)
#
cmpxchg8b_emu:
pushfl
cli
cmpl (%esi), %eax
jne not_same
cmpl 4(%esi), %edx
jne half_same
movl %ebx, (%esi)
movl %ecx, 4(%esi)
popfl
ret
not_same:
movl (%esi), %eax
half_same:
movl 4(%esi), %edx
popfl
ret
CFI_ENDPROC
ENDPROC(cmpxchg8b_emu)

View file

@ -127,7 +127,7 @@ again:
clock = wrap_max(clock, min_clock);
clock = wrap_min(clock, max_clock);
if (cmpxchg(&scd->clock, old_clock, clock) != old_clock)
if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock)
goto again;
return clock;
@ -163,7 +163,7 @@ again:
val = remote_clock;
}
if (cmpxchg(ptr, old_val, val) != old_val)
if (cmpxchg64(ptr, old_val, val) != old_val)
goto again;
return val;