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ACPI: processor: Take over RCU-idle for C3-BM idle

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The C3 BusMaster idle code takes lock in a number of places, some deep
inside the ACPI code. Instead of wrapping it all in RCU_NONIDLE, have
the driver take over RCU-idle duty and avoid flipping RCU state back
and forth a lot.

( by marking 'C3 && bm_check' as RCU_IDLE, we _must_ call enter_bm() for
  that combination, otherwise we'll loose RCU-idle, this requires
  shuffling some code around )

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Peter Zijlstra 2020-09-15 12:32:01 +02:00 committed by Rafael J. Wysocki
parent 8747f2022f
commit 1fecfdbb7a
1 changed files with 49 additions and 20 deletions
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69
drivers/acpi/processor_idle.c
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@ -558,22 +558,43 @@ static DEFINE_RAW_SPINLOCK(c3_lock);
/**
* acpi_idle_enter_bm - enters C3 with proper BM handling
* @drv: cpuidle driver
* @pr: Target processor
* @cx: Target state context
* @index: index of target state
*/
static void acpi_idle_enter_bm(struct acpi_processor *pr,
struct acpi_processor_cx *cx)
static int acpi_idle_enter_bm(struct cpuidle_driver *drv,
struct acpi_processor *pr,
struct acpi_processor_cx *cx,
int index)
{
static struct acpi_processor_cx safe_cx = {
.entry_method = ACPI_CSTATE_HALT,
};
/*
* disable bus master
* bm_check implies we need ARB_DIS
* bm_control implies whether we can do ARB_DIS
*
* That leaves a case where bm_check is set and bm_control is
* not set. In that case we cannot do much, we enter C3
* without doing anything.
* That leaves a case where bm_check is set and bm_control is not set.
* In that case we cannot do much, we enter C3 without doing anything.
*/
if (pr->flags.bm_control) {
bool dis_bm = pr->flags.bm_control;
/* If we can skip BM, demote to a safe state. */
if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
dis_bm = false;
index = drv->safe_state_index;
if (index >= 0) {
cx = this_cpu_read(acpi_cstate[index]);
} else {
cx = &safe_cx;
index = -EBUSY;
}
}
if (dis_bm) {
raw_spin_lock(&c3_lock);
c3_cpu_count++;
/* Disable bus master arbitration when all CPUs are in C3 */
@ -582,15 +603,21 @@ static void acpi_idle_enter_bm(struct acpi_processor *pr,
raw_spin_unlock(&c3_lock);
}
rcu_idle_enter();
acpi_idle_do_entry(cx);
rcu_idle_exit();
/* Re-enable bus master arbitration */
if (pr->flags.bm_control) {
if (dis_bm) {
raw_spin_lock(&c3_lock);
acpi_write_bit_register(ACPI_BITREG_ARB_DISABLE, 0);
c3_cpu_count--;
raw_spin_unlock(&c3_lock);
}
return index;
}
static int acpi_idle_enter(struct cpuidle_device *dev,
@ -604,20 +631,13 @@ static int acpi_idle_enter(struct cpuidle_device *dev,
return -EINVAL;
if (cx->type != ACPI_STATE_C1) {
if (cx->type == ACPI_STATE_C3 && pr->flags.bm_check)
return acpi_idle_enter_bm(drv, pr, cx, index);
/* C2 to C1 demotion. */
if (acpi_idle_fallback_to_c1(pr) && num_online_cpus() > 1) {
index = ACPI_IDLE_STATE_START;
cx = per_cpu(acpi_cstate[index], dev->cpu);
} else if (cx->type == ACPI_STATE_C3 && pr->flags.bm_check) {
if (cx->bm_sts_skip || !acpi_idle_bm_check()) {
acpi_idle_enter_bm(pr, cx);
return index;
} else if (drv->safe_state_index >= 0) {
index = drv->safe_state_index;
cx = per_cpu(acpi_cstate[index], dev->cpu);
} else {
acpi_safe_halt();
return -EBUSY;
}
}
}
@ -641,7 +661,13 @@ static int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
return 0;
if (pr->flags.bm_check) {
acpi_idle_enter_bm(pr, cx);
u8 bm_sts_skip = cx->bm_sts_skip;
/* Don't check BM_STS, do an unconditional ARB_DIS for S2IDLE */
cx->bm_sts_skip = 1;
acpi_idle_enter_bm(drv, pr, cx, index);
cx->bm_sts_skip = bm_sts_skip;
return 0;
} else {
ACPI_FLUSH_CPU_CACHE();
@ -674,8 +700,11 @@ static int acpi_processor_setup_cpuidle_cx(struct acpi_processor *pr,
if (lapic_timer_needs_broadcast(pr, cx))
state->flags |= CPUIDLE_FLAG_TIMER_STOP;
if (cx->type == ACPI_STATE_C3)
if (cx->type == ACPI_STATE_C3) {
state->flags |= CPUIDLE_FLAG_TLB_FLUSHED;
if (pr->flags.bm_check)
state->flags |= CPUIDLE_FLAG_RCU_IDLE;
}
count++;
if (count == CPUIDLE_STATE_MAX)