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Subject[RFC 1/2] x86/tsc: add a timer to make sure tsc_adjust is always checked
Date
Normally the tsc_sync will be checked every time system enters idle state,
but there is still caveat that a system won't enter idle, either because
it's too busy or configured purposely to not enter idle. Setup a periodic
timer to make sure the check is always on.

Signed-off-by: Feng Tang <feng.tang@intel.com>
---
arch/x86/kernel/tsc_sync.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 3d3c761..1ba3941 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -30,6 +30,7 @@ struct tsc_adjust {
};

static DEFINE_PER_CPU(struct tsc_adjust, tsc_adjust);
+static struct timer_list tsc_sync_check_timer;

/*
* TSC's on different sockets may be reset asynchronously.
@@ -77,6 +78,43 @@ void tsc_verify_tsc_adjust(bool resume)
}
}

+/*
+ * Normally the tsc_sync will be checked every time system enters idle state,
+ * but there is still caveat that a system won't enter idle, either because
+ * it's too busy or configured purposely to not enter idle.
+ *
+ * So setup a periodic timer to make sure the check is always on.
+ */
+
+#define SYNC_CHECK_INTERVAL (HZ * 600)
+static void tsc_sync_check_timer_fn(struct timer_list *unused)
+{
+ int next_cpu;
+
+ tsc_verify_tsc_adjust(false);
+
+ /* Loop to do the check for all onlined CPUs */
+ next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
+ if (next_cpu >= nr_cpu_ids)
+ next_cpu = cpumask_first(cpu_online_mask);
+
+ tsc_sync_check_timer.expires += SYNC_CHECK_INTERVAL;
+ add_timer_on(&tsc_sync_check_timer, next_cpu);
+}
+
+static int __init start_sync_check_timer(void)
+{
+ if (!boot_cpu_has(X86_FEATURE_TSC_ADJUST))
+ return 0;
+
+ timer_setup(&tsc_sync_check_timer, tsc_sync_check_timer_fn, 0);
+ tsc_sync_check_timer.expires = jiffies + SYNC_CHECK_INTERVAL;
+ add_timer(&tsc_sync_check_timer);
+
+ return 0;
+}
+late_initcall(start_sync_check_timer);
+
static void tsc_sanitize_first_cpu(struct tsc_adjust *cur, s64 bootval,
unsigned int cpu, bool bootcpu)
{
--
2.7.4
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