lkml.org 
[lkml]   [2017]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v7 1/6] x86/tsc: remove tsc_disabled flag
Date
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
\
 
 \ /
  Last update: 2017-11-02 18:28    [W:0.076 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site