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authorIngo Molnar <mingo@elte.hu>2007-02-16 01:27:34 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-16 08:13:57 -0800
commit95492e4646e5de8b43d9a7908d6177fb737b61f0 (patch)
treeae25cd206ca76f78d50ac2a206ef012e0ab1d9df /include/asm-x86_64/tsc.h
parent92c7e00254b2d0efc1e36ac3e45474ce1871b6b2 (diff)
[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>
Diffstat (limited to 'include/asm-x86_64/tsc.h')
-rw-r--r--include/asm-x86_64/tsc.h66
1 files changed, 66 insertions, 0 deletions
diff --git a/include/asm-x86_64/tsc.h b/include/asm-x86_64/tsc.h
new file mode 100644
index 00000000000..9a0a368852c
--- /dev/null
+++ b/include/asm-x86_64/tsc.h
@@ -0,0 +1,66 @@
+/*
+ * linux/include/asm-x86_64/tsc.h
+ *
+ * x86_64 TSC related functions
+ */
+#ifndef _ASM_x86_64_TSC_H
+#define _ASM_x86_64_TSC_H
+
+#include <asm/processor.h>
+
+/*
+ * Standard way to access the cycle counter.
+ */
+typedef unsigned long long cycles_t;
+
+extern unsigned int cpu_khz;
+extern unsigned int tsc_khz;
+
+static inline cycles_t get_cycles(void)
+{
+ unsigned long long ret = 0;
+
+#ifndef CONFIG_X86_TSC
+ if (!cpu_has_tsc)
+ return 0;
+#endif
+
+#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
+ rdtscll(ret);
+#endif
+ 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;
+#ifdef X86_FEATURE_SYNC_RDTSC
+ 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");
+#else
+ sync_core();
+#endif
+ rdtscll(ret);
+
+ return ret;
+}
+
+extern void tsc_init(void);
+extern void mark_tsc_unstable(void);
+extern int unsynchronized_tsc(void);
+
+/*
+ * Boot-time check whether the TSCs are synchronized across
+ * all CPUs/cores:
+ */
+extern void check_tsc_sync_source(int cpu);
+extern void check_tsc_sync_target(void);
+
+#endif