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From d4bbd21245e600f32074724152f77a4ae9904047 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Thu, 21 Apr 2016 13:49:32 +0100
Subject: [PATCH] vchiq_arm: Add completion records under the mutex
An issue was observed when flushing openmax components
which generate a large number of messages returning
buffers to host.
We occasionally found a duplicate message from 16
messages prior, resulting in a buffer returned twice.
While only one thread adds completions, without the
mutex you don't get the protection of the automatic
memory barrier you get with synchronisation objects.
Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
--- a/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -210,6 +210,8 @@ add_completion(VCHIQ_INSTANCE_T instance
VCHIQ_COMPLETION_DATA_T *completion;
DEBUG_INITIALISE(g_state.local)
+ mutex_lock(&instance->completion_mutex);
+
while (instance->completion_insert ==
(instance->completion_remove + MAX_COMPLETIONS)) {
/* Out of space - wait for the client */
@@ -217,11 +219,17 @@ add_completion(VCHIQ_INSTANCE_T instance
vchiq_log_trace(vchiq_arm_log_level,
"add_completion - completion queue full");
DEBUG_COUNT(COMPLETION_QUEUE_FULL_COUNT);
+
+ mutex_unlock(&instance->completion_mutex);
if (down_interruptible(&instance->remove_event) != 0) {
vchiq_log_info(vchiq_arm_log_level,
"service_callback interrupted");
return VCHIQ_RETRY;
- } else if (instance->closing) {
+ }
+
+ mutex_lock(&instance->completion_mutex);
+ if (instance->closing) {
+ mutex_unlock(&instance->completion_mutex);
vchiq_log_info(vchiq_arm_log_level,
"service_callback closing");
return VCHIQ_SUCCESS;
@@ -254,8 +262,11 @@ add_completion(VCHIQ_INSTANCE_T instance
if (reason == VCHIQ_MESSAGE_AVAILABLE)
user_service->message_available_pos =
instance->completion_insert;
+
instance->completion_insert++;
+ mutex_unlock(&instance->completion_mutex);
+
up(&instance->insert_event);
return VCHIQ_SUCCESS;
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