Messages in this thread Patch in this message | | | Date | Mon, 5 Dec 2011 10:03:18 -0800 | From | tip-bot for Suresh Siddha <> | Subject | [tip:timers/core] x86, tsc: Skip TSC synchronization checks for tsc=reliable |
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Commit-ID: 28a00184be261e3dc152ba0d664a067bbe235b6a Gitweb: http://git.kernel.org/tip/28a00184be261e3dc152ba0d664a067bbe235b6a Author: Suresh Siddha <suresh.b.siddha@intel.com> AuthorDate: Fri, 4 Nov 2011 15:42:17 -0700 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Mon, 5 Dec 2011 18:00:31 +0100
x86, tsc: Skip TSC synchronization checks for tsc=reliable
tsc=reliable boot parameter is supposed to skip all the TSC stablility checks during boot time.
On a 8-socket system where we want to run an experiment with the "tsc=reliable" boot option, TSC synchronization checks are not getting skipped and marking the TSC as not stable.
Check for tsc_clocksource_reliable (which is set via tsc=reliable or for platforms supporting synthetic TSC_RELIABLE feature bit etc) and when set, skip the TSC synchronization tests during boot.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/1320446537.15071.14.camel@sbsiddha-desk.sc.intel.com Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/include/asm/tsc.h | 2 ++ arch/x86/kernel/tsc.c | 2 +- arch/x86/kernel/tsc_sync.c | 4 ++-- 3 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 83e2efd..15d9915 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -51,6 +51,8 @@ extern int unsynchronized_tsc(void); extern int check_tsc_unstable(void); extern unsigned long native_calibrate_tsc(void); +extern int tsc_clocksource_reliable; + /* * Boot-time check whether the TSCs are synchronized across * all CPUs/cores: diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index db48336..eee4651 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -35,7 +35,7 @@ static int __read_mostly tsc_unstable; erroneous rdtsc usage on !cpu_has_tsc processors */ static int __read_mostly tsc_disabled = -1; -static int tsc_clocksource_reliable; +int tsc_clocksource_reliable; /* * Scheduler clock - returns current time in nanosec units. */ diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c index 0aa5fed8..9eba29b 100644 --- a/arch/x86/kernel/tsc_sync.c +++ b/arch/x86/kernel/tsc_sync.c @@ -113,7 +113,7 @@ void __cpuinit check_tsc_sync_source(int cpu) if (unsynchronized_tsc()) return; - if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) { + if (tsc_clocksource_reliable) { if (cpu == (nr_cpu_ids-1) || system_state != SYSTEM_BOOTING) pr_info( "Skipped synchronization checks as TSC is reliable.\n"); @@ -172,7 +172,7 @@ void __cpuinit check_tsc_sync_target(void) { int cpus = 2; - if (unsynchronized_tsc() || boot_cpu_has(X86_FEATURE_TSC_RELIABLE)) + if (unsynchronized_tsc() || tsc_clocksource_reliable) return; /*
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