Messages in this thread Patch in this message | | | From | Pavel Tatashin <> | Subject | [PATCH v7 1/6] x86/tsc: remove tsc_disabled flag | Date | Thu, 2 Nov 2017 13:26:39 -0400 |
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tsc_disabled is set when notsc is passed as kernel parameter. The reason we have notsc is to avoid timing problems on multi-preccors systems. However, we already have a mechanism to detect and resolve these issues by invoking tsc unstable path.
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com> --- arch/x86/kernel/tsc.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 796d96bb0821..1c4502a2b7b2 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -37,11 +37,6 @@ EXPORT_SYMBOL(tsc_khz); */ static int __read_mostly tsc_unstable; -/* native_sched_clock() is called before tsc_init(), so - we must start with the TSC soft disabled to prevent - erroneous rdtsc usage on !boot_cpu_has(X86_FEATURE_TSC) processors */ -static int __read_mostly tsc_disabled = -1; - static DEFINE_STATIC_KEY_FALSE(__use_tsc); int tsc_clocksource_reliable; @@ -248,7 +243,7 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable); int __init notsc_setup(char *str) { pr_warn("Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely\n"); - tsc_disabled = 1; + mark_tsc_unstable("boot parameter notsc"); return 1; } #else @@ -1229,7 +1224,7 @@ static void tsc_refine_calibration_work(struct work_struct *work) static int __init init_tsc_clocksource(void) { - if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz) + if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz) return 0; if (tsc_clocksource_reliable) @@ -1311,12 +1306,6 @@ void __init tsc_init(void) set_cyc2ns_scale(tsc_khz, cpu, cyc); } - if (tsc_disabled > 0) - return; - - /* now allow native_sched_clock() to use rdtsc */ - - tsc_disabled = 0; static_branch_enable(&__use_tsc); if (!no_sched_irq_time) @@ -1348,7 +1337,7 @@ unsigned long calibrate_delay_is_known(void) int sibling, cpu = smp_processor_id(); struct cpumask *mask = topology_core_cpumask(cpu); - if (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC)) + if (!cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC)) return 0; if (!mask) -- 2.15.0
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