Commit 66db3834 authored Jun 11, 2015 by Lv Zheng Committed by Rafael J. Wysocki Jun 15, 2015

ACPI / EC: Fix a code coverity issue when QR_EC transactions are failed.

When the QR_EC transaction fails, the EC_FLAGS_QUERY_PENDING flag prevents
the event handling work queue from being scheduled again.

Though there shouldn't be failed QR_EC transactions, and this gap was
efficiently used for catching and learning the SCI_EVT clearing timing
compliance issues, we need to fix this as we are not fully compatible
with all platforms/Windows to handle SCI_EVT clearing timing correctly.
Fixing this gives the EC driver the chances to recover from a state machine
failure.

So this patch fixes this issue. When nr_pending_queries drops to 0, it
clears EC_FLAGS_QUERY_PENDING at the proper position for different modes in
order to ensure that the SCI_EVT handling can proceed.

In order to be clearer for future ec_event_clearing modes, all checks in
this patch are written in the inclusive style, not the exclusive style.

Cc: 3.16+ <stable@vger.kernel.org> # 3.16+
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 3cb02aeb

drivers/acpi/ec.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -512,7 +512,8 @@ static void advance_transaction(struct acpi_ec *ec)
		*/
		if (!t \|\| !(t->flags & ACPI_EC_COMMAND_POLL)) {
		if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
		test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags)) {
		(!ec->nr_pending_queries \|\|
		test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags))) {
		clear_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);
		acpi_ec_complete_query(ec);
		}
		@@ -1065,6 +1066,17 @@ static void acpi_ec_event_handler(struct work_struct *work)
		(void)acpi_ec_query(ec, NULL);
		spin_lock_irqsave(&ec->lock, flags);
		ec->nr_pending_queries--;
		/*
		* Before exit, make sure that this work item can be
		* scheduled again. There might be QR_EC failures, leaving
		* EC_FLAGS_QUERY_PENDING uncleared and preventing this work
		* item from being scheduled again.
		*/
		if (!ec->nr_pending_queries) {
		if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS \|\|
		ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY)
		acpi_ec_complete_query(ec);
		}
		}
		spin_unlock_irqrestore(&ec->lock, flags);