Commit 737c5c3b authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
Browse files

[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: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3c021751
......@@ -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);
}
......
......@@ -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;
}
/*
......
......@@ -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 *);
......
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