Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

arch/x86_64/kernel/smpboot.c

+7 −1
Original line number Diff line number Diff line
@@ -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);

}

arch/x86_64/kernel/time.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}



/*

include/asm-x86_64/proto.h

+2 −0
Original line number Diff line number Diff line
@@ -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 *);