From 8e3fba55d379bb67732c878988cf9859bfea2812 Mon Sep 17 00:00:00 2001 From: Bryan O'Donoghue Date: Fri, 11 Dec 2015 13:46:53 +0000 Subject: [PATCH] greybus: loopback: Add asynchronous backoff A specific request from the firmware people is the ability to back-off from sending more asynchronous operations once a specific number of operations are in-flight. This patch adds that ability - with a new sysfs parameter 'outstanding_operations_max' which controls the maximum number of operations that can be outstanding/in-flight at any time. When outstanding_operations_max contains a non-zero value and asynchronous operations are being used - we will back-off until the completion counter is < outstanding_operations_max. Tested in both synchronous and asynchronous mode and with gb_loopback_connection_exit() interrupting in-flight operations. Suggested-by: Johan Hovold Signed-off-by: Bryan O'Donoghue Reviewed-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- drivers/staging/greybus/loopback.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c index 4814f94..c35d227 100644 --- a/drivers/staging/greybus/loopback.c +++ b/drivers/staging/greybus/loopback.c @@ -98,6 +98,7 @@ struct gb_loopback { u32 jiffy_timeout; u32 timeout_min; u32 timeout_max; + u32 outstanding_operations_max; u32 lbid; u64 elapsed_nsecs; u32 apbridge_latency_ts; @@ -311,6 +312,8 @@ gb_dev_loopback_ro_attr(iteration_count, false); gb_dev_loopback_rw_attr(async, u); /* Timeout of an individual asynchronous request */ gb_dev_loopback_rw_attr(timeout, u); +/* Maximum number of in-flight operations before back-off */ +gb_dev_loopback_rw_attr(outstanding_operations_max, u); static struct attribute *loopback_attrs[] = { &dev_attr_latency_min.attr, @@ -338,6 +341,7 @@ static struct attribute *loopback_attrs[] = { &dev_attr_requests_completed.attr, &dev_attr_requests_timedout.attr, &dev_attr_timeout.attr, + &dev_attr_outstanding_operations_max.attr, &dev_attr_timeout_min.attr, &dev_attr_timeout_max.attr, NULL, @@ -911,6 +915,16 @@ static void gb_loopback_calculate_stats(struct gb_loopback *gb) gb->gpbridge_latency_ts); } +static void gb_loopback_async_wait_to_send(struct gb_loopback *gb) +{ + if (!(gb->async && gb->outstanding_operations_max)) + return; + wait_event_interruptible(gb->wq_completion, + (atomic_read(&gb->outstanding_operations) < + gb->outstanding_operations_max) || + kthread_should_stop()); +} + static int gb_loopback_fn(void *data) { int error = 0; @@ -924,7 +938,11 @@ static int gb_loopback_fn(void *data) if (!gb->type) wait_event_interruptible(gb->wq, gb->type || kthread_should_stop()); + if (kthread_should_stop()) + break; + /* Limit the maximum number of in-flight async operations */ + gb_loopback_async_wait_to_send(gb); if (kthread_should_stop()) break; -- 2.7.4