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: 56b991849009 ("PM: sleep: Simplify suspend-to-idle control flow")
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 4a230c2f1c31..2b2055b035ee 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -191,7 +191,7 @@ struct platform_s2idle_ops {
 	int (*begin)(void);
 	int (*prepare)(void);
 	int (*prepare_late)(void);
-	void (*wake)(void);
+	bool (*wake)(void);
 	void (*restore_early)(void);
 	void (*restore)(void);
 	void (*end)(void);