linux-kernel - [PATCH 1/3] acpi: Rip out EC_FLAGS_QUERY

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Date:	Sat, 19 Jul 2008 12:38:33 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
CC:	Alexey Starikovskiy <astarikovskiy@...e.de>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] acpi: Rip out EC_FLAGS_QUERY_PENDING (prevent race condition)

From: Alan Jenkins <alan-jenkins@...fmail.co.uk>

If several GPE interrupts arrive at a time, then perform an equal number of
queries in the workqueue.  It doesn't matter if there are excess interrupts;
the queries will just come back with nothing.

This won't fix anything, because it still switches to polling GPEs if more
than five interrupts arrive at a time.  But it simplifies the code, and makes
it easier to modify further without introducing race conditions.

Signed-off-by: Alan Jenkins <alan-jenkins@...fmail.co.uk>
Tested-by: Alan Jenkins <alan-jenkins@...fmail.co.uk>

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 5622aee..8e4b1a4 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -77,7 +77,6 @@ enum ec_event {
 
 enum {
 	EC_FLAGS_WAIT_GPE = 0,		/* Don't check status until GPE arrives */
-	EC_FLAGS_QUERY_PENDING,		/* Query is pending */
 	EC_FLAGS_GPE_MODE,		/* Expect GPE to be sent for status change */
 	EC_FLAGS_NO_GPE,		/* Don't use GPE mode */
 	EC_FLAGS_RESCHEDULE_POLL	/* Re-schedule poll */
@@ -230,8 +229,7 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec, u8 command,
 			       "finish-write timeout, command = %d\n", command);
 			goto end;
 		}
-	} else if (command == ACPI_EC_COMMAND_QUERY)
-		clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
+	}
 
 	for (; rdata_len > 0; --rdata_len) {
 		result = acpi_ec_wait(ec, ACPI_EC_EVENT_OBF_1, force_poll);
@@ -502,7 +508,7 @@ static u32 acpi_ec_gpe_handler(void *data)
 		wake_up(&ec->wait);
 
 	if (state & ACPI_EC_FLAG_SCI) {
-		if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
+		if (ec->handlers_installed)
 			status = acpi_os_execute(OSL_EC_BURST_HANDLER,
 				acpi_ec_gpe_query, ec);
 	} else if (!test_bit(EC_FLAGS_GPE_MODE, &ec->flags) &&
@@ -665,7 +671,6 @@ static struct acpi_ec *make_acpi_ec(void)
 	struct acpi_ec *ec = kzalloc(sizeof(struct acpi_ec), GFP_KERNEL);
 	if (!ec)
 		return NULL;
-	ec->flags = 1 << EC_FLAGS_QUERY_PENDING;
 	mutex_init(&ec->lock);
 	init_waitqueue_head(&ec->wait);
 	INIT_LIST_HEAD(&ec->list);
@@ -858,8 +863,6 @@ static int acpi_ec_start(struct acpi_device *device)
 
 	ret = ec_install_handlers(ec);
 
-	/* EC is fully operational, allow queries */
-	clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags);
 	ec_schedule_ec_poll(ec);
 	return ret;
 }


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