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From: john stultz <johnstul@us.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Andi Kleen <ak@suse.de>, lkml <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs (resend)
Date: Mon, 26 Sep 2005 12:46:52 -0700	[thread overview]
Message-ID: <1127764012.8195.138.camel@cog.beaverton.ibm.com> (raw)

Andrew,
	This patch should resolve the issue seen in bugme bug #5105, where it
is assumed that dualcore x86_64 systems have synced TSCs. This is not
the case, and alternate timesources should be used instead.

For more details, see:
http://bugzilla.kernel.org/show_bug.cgi?id=5105

Andi's earlier concerns that the TSCs should be synced on dualcore
systems have been resolved by confirmation from AMD folks that they can
be unsynced.

Please consider for inclusion in your tree.

thanks
-john

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -959,9 +959,6 @@ static __init int unsynchronized_tsc(voi
  	   are handled in the OEM check above. */
  	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
  		return 0;
- 	/* All in a single socket - should be synchronized */
- 	if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
- 		return 0;
 #endif
  	/* Assume multi socket systems are not synchronized */
  	return num_online_cpus() > 1;



             reply	other threads:[~2005-09-26 19:47 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-09-26 19:46 john stultz [this message]
2005-09-26 20:33 ` Andrew Morton
2005-09-27  8:34   ` Andi Kleen
2005-09-26 22:15 ` Stefan Smietanowski
2005-09-26 22:28   ` john stultz
2005-09-26 23:31     ` Stefan Smietanowski

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