From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lv Zheng Subject: [PATCH v2] ACPI / EC: Fix a regression by reducing parallel _Qxx evaluations Date: Wed, 3 Aug 2016 09:00:14 +0800 Message-ID: References: Return-path: Received: from mga02.intel.com ([134.134.136.20]:57275 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756821AbcHCBAc (ORCPT ); Tue, 2 Aug 2016 21:00:32 -0400 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: "Rafael J. Wysocki" , "Rafael J. Wysocki" , Len Brown Cc: Lv Zheng , Lv Zheng , linux-acpi@vger.kernel.org, Wei Yongjun 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) Cc: # 4.3+ Reported-and-tested-by: Helen Buus Signed-off-by: Lv Zheng Cc: Wei Yongjun --- 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 999a109..e7bd57c 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; } @@ -1660,15 +1666,41 @@ 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; } @@ -1678,5 +1710,6 @@ static void __exit acpi_ec_exit(void) { acpi_bus_unregister_driver(&acpi_ec_driver); + acpi_ec_query_exit(); } #endif /* 0 */ -- 1.7.10