Hi, Rafael > From: Zheng, Lv > Subject: [PATCH] ACPI / EC: Fix a regression by reducing parallel _Qxx > evaluations > > 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: <stable@xxxxxxxxxxxxxxx> # 4.3+ > Reported-and-tested-by: Helen Buus <ubuntu@xxxxxxxxx> [Lv Zheng] I'm sorry that I forgot to mention the bug link. It's actually recorded in kernel Bugzilla. The bug can be found here: Link: https://bugzilla.kernel.org/show_bug.cgi?id=135691 Hope you can help to add this useful information if this patch is acceptable. Best regards -Lv > Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx> > --- > drivers/acpi/ec.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c > index 999a109..907b450 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; > } > @@ -1664,6 +1670,10 @@ int __init acpi_ec_init(void) > { > int result = 0; > > + ec_query_wq = alloc_workqueue("kec_query", 0, ec_max_queries); > + if (!ec_query_wq) > + return -ENODEV; > + > /* Now register the driver for the EC */ > result = acpi_bus_register_driver(&acpi_ec_driver); > if (result < 0) > @@ -1678,5 +1688,6 @@ static void __exit acpi_ec_exit(void) > { > > acpi_bus_unregister_driver(&acpi_ec_driver); > + destroy_workqueue(ec_query_wq); > } > #endif /* 0 */ > -- > 1.7.10 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
