Commit e3728b50 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki

ACPI: PM: s2idle: Avoid possible race related to the EC GPE

It is theoretically possible for the ACPI EC GPE to be set after the
s2idle_ops->wake() called from s2idle_loop() has returned and before
the subsequent pm_wakeup_pending() check is carried out.  If that
happens, the resulting wakeup event will cause the system to resume
even though it may be a spurious one.

To avoid that race, first make the ->wake() callback in struct
platform_s2idle_ops return a bool value indicating whether or not
to let the system resume and rearrange s2idle_loop() to use that
value instad of the direct pm_wakeup_pending() call if ->wake() is
present.

Next, rework acpi_s2idle_wake() to process EC events and check
pm_wakeup_pending() before re-arming the SCI for system wakeup
to prevent it from triggering prematurely and add comments to
that function to explain the rationale for the new code flow.

Fixes: 56b99184 ("PM: sleep: Simplify suspend-to-idle control flow")
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent f0ac20c3
...@@ -990,21 +990,28 @@ static void acpi_s2idle_sync(void) ...@@ -990,21 +990,28 @@ static void acpi_s2idle_sync(void)
acpi_os_wait_events_complete(); /* synchronize Notify handling */ acpi_os_wait_events_complete(); /* synchronize Notify handling */
} }
static void acpi_s2idle_wake(void) static bool acpi_s2idle_wake(void)
{ {
if (!acpi_sci_irq_valid())
return pm_wakeup_pending();
while (pm_wakeup_pending()) {
/* /*
* If IRQD_WAKEUP_ARMED is set for the SCI at this point, the SCI has * If IRQD_WAKEUP_ARMED is set for the SCI at this point, the
* not triggered while suspended, so bail out. * SCI has not triggered while suspended, so bail out (the
* wakeup is pending anyway and the SCI is not the source of
* it).
*/ */
if (!acpi_sci_irq_valid() || if (irqd_is_wakeup_armed(irq_get_irq_data(acpi_sci_irq)))
irqd_is_wakeup_armed(irq_get_irq_data(acpi_sci_irq))) return true;
return;
/* /*
* If there are EC events to process, the wakeup may be a spurious one * If there are no EC events to process, the wakeup is regarded
* coming from the EC. * as a genuine one.
*/ */
if (acpi_ec_dispatch_gpe()) { if (!acpi_ec_dispatch_gpe())
return true;
/* /*
* Cancel the wakeup and process all pending events in case * Cancel the wakeup and process all pending events in case
* there are any wakeup ones in there. * there are any wakeup ones in there.
...@@ -1017,8 +1024,19 @@ static void acpi_s2idle_wake(void) ...@@ -1017,8 +1024,19 @@ static void acpi_s2idle_wake(void)
acpi_s2idle_sync(); acpi_s2idle_sync();
/*
* The SCI is in the "suspended" state now and it cannot produce
* new wakeup events till the rearming below, so if any of them
* are pending here, they must be resulting from the processing
* of EC events above or coming from somewhere else.
*/
if (pm_wakeup_pending())
return true;
rearm_wake_irq(acpi_sci_irq); rearm_wake_irq(acpi_sci_irq);
} }
return false;
} }
static void acpi_s2idle_restore_early(void) static void acpi_s2idle_restore_early(void)
......
...@@ -191,7 +191,7 @@ struct platform_s2idle_ops { ...@@ -191,7 +191,7 @@ struct platform_s2idle_ops {
int (*begin)(void); int (*begin)(void);
int (*prepare)(void); int (*prepare)(void);
int (*prepare_late)(void); int (*prepare_late)(void);
void (*wake)(void); bool (*wake)(void);
void (*restore_early)(void); void (*restore_early)(void);
void (*restore)(void); void (*restore)(void);
void (*end)(void); void (*end)(void);
......
...@@ -131,11 +131,12 @@ static void s2idle_loop(void) ...@@ -131,11 +131,12 @@ static void s2idle_loop(void)
* to avoid them upfront. * to avoid them upfront.
*/ */
for (;;) { for (;;) {
if (s2idle_ops && s2idle_ops->wake) if (s2idle_ops && s2idle_ops->wake) {
s2idle_ops->wake(); if (s2idle_ops->wake())
if (pm_wakeup_pending())
break; break;
} else if (pm_wakeup_pending()) {
break;
}
pm_wakeup_clear(false); pm_wakeup_clear(false);
......
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