[PATCH 1/3] acpi: Rip out EC_FLAGS_QUERY_PENDING (prevent race condition)

Alan Jenkins
2008-07-19T11:38:23Z

From: Alan Jenkins <alan-jenkins@tuffmail.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@tuffmail.co.uk>
Tested-by: Alan Jenkins <alan-jenkins@tuffmail.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;
}