From e370cc8640305aa2fa42b852cccd89e80c28d9a0 Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Date: Fri, 29 Jul 2016 17:08:41 +0200
Subject: [PATCH 1/2] ACPI / button: remove pointer to old lid_sysfs on unbind

When we removed the procfs dir on error or if the driver is
unbound, the two variables acpi_lid_dir and acpi_button_dir
were not reset. On the next rebind, those static variables
were not null and we couldn't re-register the device again.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/button.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 148f4e5ca104b..31abb0bdd4f29 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -232,8 +232,10 @@ static int acpi_button_add_fs(struct acpi_device *device)
 	acpi_device_dir(device) = NULL;
 remove_lid_dir:
 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
+	acpi_lid_dir = NULL;
 remove_button_dir:
 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
+	acpi_button_dir = NULL;
 	goto done;
 }
 
@@ -250,7 +252,9 @@ static int acpi_button_remove_fs(struct acpi_device *device)
 			  acpi_lid_dir);
 	acpi_device_dir(device) = NULL;
 	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID, acpi_button_dir);
+	acpi_lid_dir = NULL;
 	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
+	acpi_button_dir = NULL;
 
 	return 0;
 }

From e1191bd4f62d9086a1a47adc286e7fcffc1fa55c Mon Sep 17 00:00:00 2001
From: Lv Zheng <lv.zheng@intel.com>
Date: Wed, 3 Aug 2016 09:00:14 +0800
Subject: [PATCH 2/2] ACPI / EC: Work around method reentrancy limit in ACPICA
 for _Qxx

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
Cc: 4.3+ <stable@vger.kernel.org> # 4.3+
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>
---
 drivers/acpi/ec.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index b1050a0c10fba..13d1b94879904 100644
--- 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_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 */