perf counters: protect them against CSTATE transitions
Impact: fix rare lost events problem
There are CPUs whose performance counters misbehave on CSTATE transitions,
so provide a way to just disable/enable them around deep idle methods.
(hw_perf_enable_all() is cheap on x86.)
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 5f8d746..cca804e 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -270,8 +270,11 @@
/* Common C-state entry for C2, C3, .. */
static void acpi_cstate_enter(struct acpi_processor_cx *cstate)
{
+ u64 pctrl;
+
/* Don't trace irqs off for idle */
stop_critical_timings();
+ pctrl = hw_perf_disable_all();
if (cstate->entry_method == ACPI_CSTATE_FFH) {
/* Call into architectural FFH based C-state */
acpi_processor_ffh_cstate_enter(cstate);
@@ -284,6 +287,7 @@
gets asserted in time to freeze execution properly. */
unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
}
+ hw_perf_restore_ctrl(pctrl);
start_critical_timings();
}
#endif /* !CONFIG_CPU_IDLE */
@@ -1425,8 +1429,11 @@
*/
static inline void acpi_idle_do_entry(struct acpi_processor_cx *cx)
{
+ u64 pctrl;
+
/* Don't trace irqs off for idle */
stop_critical_timings();
+ pctrl = hw_perf_disable_all();
if (cx->entry_method == ACPI_CSTATE_FFH) {
/* Call into architectural FFH based C-state */
acpi_processor_ffh_cstate_enter(cx);
@@ -1441,6 +1448,7 @@
gets asserted in time to freeze execution properly. */
unused = inl(acpi_gbl_FADT.xpm_timer_block.address);
}
+ hw_perf_restore_ctrl(pctrl);
start_critical_timings();
}