diff options
| author | Andi Kleen <ak@suse.de> | 2006-01-11 22:45:15 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-11 19:04:57 -0800 |
| commit | 737c5c3bde5641af9c24e3a60366674af72a43ef (patch) | |
| tree | e369c6489279c9fda4a5fb1766fe1966ce9caf87 | |
| parent | 3c0217511313a46039137d2dab30fdb1c5a65e64 (diff) | |
[PATCH] x86_64: Don't try to synchronize the TSC over CPUs on Intel CPUs at boot.
They already do this in hardware and the Linux algorithm
actually adds errors.
Cc: mingo@elte.hu
Cc: rohit.seth@intel.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | arch/x86_64/kernel/smpboot.c | 8 | ||||
| -rw-r--r-- | arch/x86_64/kernel/time.c | 4 | ||||
| -rw-r--r-- | include/asm-x86_64/proto.h | 2 |
3 files changed, 11 insertions, 3 deletions
diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c index e6af93b51dce..994728564d6b 100644 --- a/arch/x86_64/kernel/smpboot.c +++ b/arch/x86_64/kernel/smpboot.c @@ -335,7 +335,13 @@ static __cpuinit void sync_tsc(unsigned int master) static void __cpuinit tsc_sync_wait(void) { - if (notscsync || !cpu_has_tsc) + /* + * When the CPU has synchronized TSCs assume the BIOS + * or the hardware already synced. Otherwise we could + * mess up a possible perfect synchronization with a + * not-quite-perfect algorithm. + */ + if (notscsync || !cpu_has_tsc || !unsynchronized_tsc()) return; sync_tsc(0); } diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 211bf0e51d9d..f8d4b69388d2 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -953,7 +953,7 @@ void __init time_init(void) * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. */ -static __init int unsynchronized_tsc(void) +__init int unsynchronized_tsc(void) { #ifdef CONFIG_SMP if (oem_force_hpet_timer()) @@ -964,7 +964,7 @@ static __init int unsynchronized_tsc(void) return 0; #endif /* Assume multi socket systems are not synchronized */ - return num_online_cpus() > 1; + return num_present_cpus() > 1; } /* diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h index 56dc70b7a6e4..115e496c6139 100644 --- a/include/asm-x86_64/proto.h +++ b/include/asm-x86_64/proto.h @@ -89,6 +89,8 @@ extern void check_efer(void); extern int unhandled_signal(struct task_struct *tsk, int sig); +extern int unsynchronized_tsc(void); + extern void select_idle_routine(const struct cpuinfo_x86 *c); extern void gart_parse_options(char *); |