Commit e1191bd4 authored by Lv Zheng's avatar Lv Zheng Committed by Rafael J. Wysocki
Browse files

ACPI / EC: Work around method reentrancy limit in ACPICA for _Qxx 

A regression is caused by the following commit:

  Commit: 02b771b6
  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: 02b771b6 (ACPI / EC: Fix an issue caused by the serialized _Qxx evaluations)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=135691


Cc: 4.3+ <stable@vger.kernel.org> # 4.3+
Reported-and-tested-by: default avatarHelen Buus <ubuntu@hbuus.com>
Signed-off-by: default avatarLv Zheng <lv.zheng@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent bc539567

drivers/acpi/ec.c

+37 −4
Original line number Diff line number Diff line
@@ -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_mostly = ACPI_EC_DELAY; 
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(struct work_struct *work); 


struct acpi_ec *boot_ec, *first_ec;

EXPORT_SYMBOL(first_ec);

static struct workqueue_struct *ec_query_wq;



static int EC_FLAGS_CLEAR_ON_RESUME; /* Needs acpi_ec_clear() on boot/resume */

static int EC_FLAGS_QUERY_HANDSHAKE; /* Needs QR_EC issued when SCI_EVT set */
@@ -1098,7 +1104,7 @@ static int acpi_ec_query(struct acpi_ec *ec, u8 *data) 
	 * 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;

	}
@@ -1649,15 +1655,41 @@ 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;

}
@@ -1667,5 +1699,6 @@ static void __exit acpi_ec_exit(void) 
{



	acpi_bus_unregister_driver(&acpi_ec_driver);

	acpi_ec_query_exit();

}

#endif	/* 0 */

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