[PATCH] x86: rewrite SMP TSC sync code

make the TSC synchronization code more robust, and unify it between x86_64 and
i386.

The biggest change is the removal of the 'fix up TSCs' code on x86_64 and
i386, in some rare cases it was /causing/ time-warps on SMP systems.

The new code only checks for TSC asynchronity - and if it can prove a
time-warp (if it can observe the TSC going backwards when going from one CPU
to another within a critical section), then the TSC clock-source is turned
off.

The TSC synchronization-checking code also got moved into a separate file.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 25 deletions

diff --git a/include/asm-x86_64/timex.h b/include/asm-x86_64/timex.h
index b9e5320..a4493a7 100644
--- a/include/asm-x86_64/timex.h
+++ b/include/asm-x86_64/timex.h
@@ -12,35 +12,11 @@
 #include <asm/hpet.h>
 #include <asm/system.h>
 #include <asm/processor.h>
+#include <asm/tsc.h>
 #include <linux/compiler.h>
 
 #define CLOCK_TICK_RATE	PIT_TICK_RATE	/* Underlying HZ */
 
-typedef unsigned long long cycles_t;
-
-static inline cycles_t get_cycles (void)
-{
-	unsigned long long ret;
-
-	rdtscll(ret);
-	return ret;
-}
-
-/* Like get_cycles, but make sure the CPU is synchronized. */
-static __always_inline cycles_t get_cycles_sync(void)
-{
-	unsigned long long ret;
-	unsigned eax;
-	/* Don't do an additional sync on CPUs where we know
-	   RDTSC is already synchronous. */
-	alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
-			  "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
-	rdtscll(ret);
-	return ret;
-}
-
-extern unsigned int cpu_khz;
-
 extern int read_current_timer(unsigned long *timer_value);
 #define ARCH_HAS_READ_CURRENT_TIMER	1