linux-kernel - [RFC patch] need check TSC wrap unconditionally

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Date:	Fri, 14 Aug 2009 12:15:00 +0800
From:	Luming Yu <luming.yu@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Subject: [RFC patch] need check TSC wrap unconditionally

Hi there,

we disabled tsc wrap check on any platform that has NOSTOP_TSC cpu. But this
will cause some real problem.For example, 1.CPU does has constant and
non_stop tsc, which means different CPU ticks at same rate in same domain,but
have been given different initial TSC value.Then at any given time,
CPUsare unsynchronized.
2. if those CPUs are sit in different domain..(multi-chassis cluster system?)

Please review. If make sense, please apply.

**The patch is enclosed in text attachment*
**Using web client to send the patch* *
**below is for review, please apply attached  patch*/

Thanks,
Luming

Signed-off-by: Yu Luming <luming.yu@...el.com>

 arch/x86/kernel/tsc_sync.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 027b5b4..312ba84 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -113,11 +113,6 @@ void __cpuinit check_tsc_sync_source(int cpu)
        if (unsynchronized_tsc())
                return;

-       if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) {
-               pr_info("Skipping synchronization checks as TSC is
reliable.\n");
-               return;
-       }
-
        pr_info("checking TSC synchronization [CPU#%d -> CPU#%d]:",
                smp_processor_id(), cpu);

@@ -171,7 +166,7 @@ void __cpuinit check_tsc_sync_target(void)
 {
        int cpus = 2;

-       if (unsynchronized_tsc() || boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
+       if (unsynchronized_tsc())
                return;

        /*

Download attachment "7" of type "application/octet-stream" (700 bytes)