[PATCH 4.4 133/138] ACPI / EC: Work around method reentrancy limit in ACPICA for _Qxx

Greg Kroah-Hartman
2016-08-18T14:18:51Z

From: Lv Zheng <lv.zheng@intel.com>

commit e1191bd4f62d9086a1a47adc286e7fcffc1fa55c upstream.

A regression is caused by the following commit:

Commit: 02b771b64b73226052d6e731a0987db3b47281e9
Subject: ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations

In this commit, using system workqueue causes that the maximum parallel
executions of _Qxx can exceed 255. This violates the method reentrancy
limit in ACPICA and generates the following error log:

ACPI Error: Method reached maximum reentrancy limit (255) (20150818/dsmethod-341)

This patch creates a seperate workqueue and limits the number of parallel
_Qxx evaluations down to a configurable value (can be tuned against number
of online CPUs).

Since EC events are handled after driver probe, we can create the workqueue
in acpi_ec_init().

Fixes: 02b771b64b73 (ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=135691
Reported-and-tested-by: Helen Buus <ubuntu@hbuus.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/acpi/ec.c | 41 +++++++++++++++++++++++++++++++++++++----
1 file changed, 37 insertions(+), 4 deletions(-)

--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -101,6 +101,7 @@ enum ec_command {
#define ACPI_EC_UDELAY_POLL 550 /* Wait 1ms for EC transaction polling */
#define ACPI_EC_CLEAR_MAX 100 /* Maximum number of events to query
* when trying to clear the EC */
+#define ACPI_EC_MAX_QUERIES 16 /* Maximum number of parallel queries */

enum {
EC_FLAGS_QUERY_PENDING, /* Query is pending */
@@ -121,6 +122,10 @@ static unsigned int ec_delay __read_most
module_param(ec_delay, uint, 0644);
MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");

+static unsigned int ec_max_queries __read_mostly = ACPI_EC_MAX_QUERIES;
+module_param(ec_max_queries, uint, 0644);
+MODULE_PARM_DESC(ec_max_queries, "Maximum parallel _Qxx evaluations");
+
static bool ec_busy_polling __read_mostly;
module_param(ec_busy_polling, bool, 0644);
MODULE_PARM_DESC(ec_busy_polling, "Use busy polling to advance EC transaction");
@@ -174,6 +179,7 @@ static void acpi_ec_event_processor(stru

struct acpi_ec *boot_ec, *first_ec;
EXPORT_SYMBOL(first_ec);
+static struct workqueue_struct *ec_query_wq;

static int EC_FLAGS_VALIDATE_ECDT; /* ASUStec ECDTs need to be validated */
static int EC_FLAGS_SKIP_DSDT_SCAN; /* Not all BIOS survive early DSDT scan */
@@ -1097,7 +1103,7 @@ static int acpi_ec_query(struct acpi_ec
* work queue execution.
*/
ec_dbg_evt("Query(0x%02x) scheduled", value);
- if (!schedule_work(&q->work)) {
+ if (!queue_work(ec_query_wq, &q->work)) {
ec_dbg_evt("Query(0x%02x) overlapped", value);
result = -EBUSY;
}
@@ -1657,15 +1663,41 @@ static struct acpi_driver acpi_ec_driver
},
};

+static inline int acpi_ec_query_init(void)
+{
+ if (!ec_query_wq) {
+ ec_query_wq = alloc_workqueue("kec_query", 0,
+ ec_max_queries);
+ if (!ec_query_wq)
+ return -ENODEV;
+ }
+ return 0;
+}
+
+static inline void acpi_ec_query_exit(void)
+{
+ if (ec_query_wq) {
+ destroy_workqueue(ec_query_wq);
+ ec_query_wq = NULL;
+ }
+}
+
int __init acpi_ec_init(void)
{
- int result = 0;
+ int result;

+ /* register workqueue for _Qxx evaluations */
+ result = acpi_ec_query_init();
+ if (result)
+ goto err_exit;
/* Now register the driver for the EC */
result = acpi_bus_register_driver(&acpi_ec_driver);
- if (result < 0)
- return -ENODEV;
+ if (result)
+ goto err_exit;

+err_exit:
+ if (result)
+ acpi_ec_query_exit();
return result;
}

@@ -1675,5 +1707,6 @@ static void __exit acpi_ec_exit(void)
{

acpi_bus_unregister_driver(&acpi_ec_driver);
+ acpi_ec_query_exit();
}
#endif /* 0 */