Messages in this thread | | | Subject | Re: [PATCH v8 1/6] x86/tsc: remove tsc_disabled flag | From | Dou Liyang <> | Date | Mon, 13 Nov 2017 11:52:14 +0800 |
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Hi Pavel,
At 11/09/2017 11:01 AM, Pavel Tatashin wrote: > tsc_disabled is set when notsc is passed as kernel parameter. The reason we > have notsc is to avoid timing problems on multi-socket systems. We already > have a mechanism, however, to detect and resolve these issues by invoking > tsc unstable path. Thus, make notsc to behave the same as tsc=unstable. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
I am not sure if I could add the signature.
Anyway, it looks good to me.
Reviewed-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
> --- > arch/x86/kernel/tsc.c | 19 +++---------------- > 1 file changed, 3 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > index 97907e152356..dbce6fa32aa9 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; > @@ -247,8 +242,7 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable); > #ifdef CONFIG_X86_TSC > 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 +1223,7 @@ 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) > @@ -1330,12 +1324,6 @@ 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) > @@ -1365,10 +1353,9 @@ void __init tsc_init(void) > unsigned long calibrate_delay_is_known(void) > { > int sibling, cpu = smp_processor_id(); > - int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC); > const struct cpumask *mask = topology_core_cpumask(cpu); > > - if (tsc_disabled || !constant_tsc || !mask) > + if (!cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC) || !mask) > return 0; > > sibling = cpumask_any_but(mask, cpu); >
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