diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2017-05-05 09:55:01 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-15 10:15:16 +0200 |
| commit | 615cd03373a02a17b82b253ff5e02e3a83b224f8 (patch) | |
| tree | 1188df49f87e3051e368a373609d2bc5e9e2bd7a /arch/x86 | |
| parent | 59eaef78bfea88fcbbd7b9b48ccf513aae1522c3 (diff) | |
x86/tsc: Fix sched_clock() sync
While looking through the code I noticed that we initialize the cyc2ns
fields with a different cycle value for each CPU, resulting in a
slightly different 0 point for each CPU.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 23ce8b9a5d1f..dda964c6387d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -137,9 +137,9 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc) return ns; } -static void set_cyc2ns_scale(unsigned long khz, int cpu) +static void __set_cyc2ns_scale(unsigned long khz, int cpu, unsigned long long tsc_now) { - unsigned long long tsc_now, ns_now; + unsigned long long ns_now; struct cyc2ns_data data; struct cyc2ns *c2n; unsigned long flags; @@ -150,7 +150,6 @@ static void set_cyc2ns_scale(unsigned long khz, int cpu) if (!khz) goto done; - tsc_now = rdtsc(); ns_now = cycles_2_ns(tsc_now); /* @@ -186,6 +185,12 @@ done: sched_clock_idle_wakeup_event(0); local_irq_restore(flags); } + +static void set_cyc2ns_scale(unsigned long khz, int cpu) +{ + __set_cyc2ns_scale(khz, cpu, rdtsc()); +} + /* * Scheduler clock - returns current time in nanosec units. */ @@ -1251,7 +1256,7 @@ device_initcall(init_tsc_clocksource); void __init tsc_init(void) { - u64 lpj; + u64 lpj, cyc; int cpu; if (!boot_cpu_has(X86_FEATURE_TSC)) { @@ -1291,9 +1296,10 @@ void __init tsc_init(void) * speed as the bootup CPU. (cpufreq notifiers will fix this * up if their speed diverges) */ + cyc = rdtsc(); for_each_possible_cpu(cpu) { cyc2ns_init(cpu); - set_cyc2ns_scale(tsc_khz, cpu); + __set_cyc2ns_scale(tsc_khz, cpu, cyc); } if (tsc_disabled > 0) |