+++ /dev/null
-From c1aad7829f0bb4f13b6a61879361f2405eed2a9b Mon Sep 17 00:00:00 2001
-From: Phil Elwell <phil@raspberrypi.org>
-Date: Mon, 20 Jun 2016 13:51:44 +0100
-Subject: [PATCH] vchiq_arm: Avoid use of mutex in add_completion
-
-Claiming the completion_mutex within add_completion did prevent some
-messages appearing twice, but provokes a deadlock caused by vcsm using
-vchiq within a page fault handler.
-
-Revert the use of completion_mutex, and instead fix the original
-problem using more memory barriers.
-
-Signed-off-by: Phil Elwell <phil@raspberrypi.org>
----
- .../vc04_services/interface/vchiq_arm/vchiq_arm.c | 55 +++++++++++-----------
- .../vc04_services/interface/vchiq_arm/vchiq_core.c | 14 ++++--
- 2 files changed, 37 insertions(+), 32 deletions(-)
-
---- a/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c
-+++ b/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_arm.c
-@@ -64,10 +64,10 @@
- #define VCHIQ_MINOR 0
-
- /* Some per-instance constants */
--#define MAX_COMPLETIONS 16
-+#define MAX_COMPLETIONS 128
- #define MAX_SERVICES 64
- #define MAX_ELEMENTS 8
--#define MSG_QUEUE_SIZE 64
-+#define MSG_QUEUE_SIZE 128
-
- #define KEEPALIVE_VER 1
- #define KEEPALIVE_VER_MIN KEEPALIVE_VER
-@@ -208,28 +208,24 @@ add_completion(VCHIQ_INSTANCE_T instance
- void *bulk_userdata)
- {
- VCHIQ_COMPLETION_DATA_T *completion;
-+ int insert;
- DEBUG_INITIALISE(g_state.local)
-
-- mutex_lock(&instance->completion_mutex);
--
-- while (instance->completion_insert ==
-- (instance->completion_remove + MAX_COMPLETIONS)) {
-+ insert = instance->completion_insert;
-+ while ((insert - instance->completion_remove) >= MAX_COMPLETIONS) {
- /* Out of space - wait for the client */
- DEBUG_TRACE(SERVICE_CALLBACK_LINE);
- 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;
- }
-
-- 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;
-@@ -237,9 +233,7 @@ add_completion(VCHIQ_INSTANCE_T instance
- DEBUG_TRACE(SERVICE_CALLBACK_LINE);
- }
-
-- completion =
-- &instance->completions[instance->completion_insert &
-- (MAX_COMPLETIONS - 1)];
-+ completion = &instance->completions[insert & (MAX_COMPLETIONS - 1)];
-
- completion->header = header;
- completion->reason = reason;
-@@ -260,12 +254,9 @@ add_completion(VCHIQ_INSTANCE_T instance
- wmb();
-
- if (reason == VCHIQ_MESSAGE_AVAILABLE)
-- user_service->message_available_pos =
-- instance->completion_insert;
--
-- instance->completion_insert++;
-+ user_service->message_available_pos = insert;
-
-- mutex_unlock(&instance->completion_mutex);
-+ instance->completion_insert = ++insert;
-
- up(&instance->insert_event);
-
-@@ -795,6 +786,7 @@ vchiq_ioctl(struct file *file, unsigned
- instance->completion_insert)
- && !instance->closing) {
- int rc;
-+
- DEBUG_TRACE(AWAIT_COMPLETION_LINE);
- mutex_unlock(&instance->completion_mutex);
- rc = down_interruptible(&instance->insert_event);
-@@ -809,24 +801,29 @@ vchiq_ioctl(struct file *file, unsigned
- }
- DEBUG_TRACE(AWAIT_COMPLETION_LINE);
-
-- /* A read memory barrier is needed to stop prefetch of a stale
-- ** completion record
-- */
-- rmb();
--
- if (ret == 0) {
- int msgbufcount = args.msgbufcount;
-+ int remove;
-+
-+ remove = instance->completion_remove;
-+
- for (ret = 0; ret < args.count; ret++) {
- VCHIQ_COMPLETION_DATA_T *completion;
- VCHIQ_SERVICE_T *service;
- USER_SERVICE_T *user_service;
- VCHIQ_HEADER_T *header;
-- if (instance->completion_remove ==
-- instance->completion_insert)
-+
-+ if (remove == instance->completion_insert)
- break;
-+
- completion = &instance->completions[
-- instance->completion_remove &
-- (MAX_COMPLETIONS - 1)];
-+ remove & (MAX_COMPLETIONS - 1)];
-+
-+
-+ /* A read memory barrier is needed to prevent
-+ ** the prefetch of a stale completion record
-+ */
-+ rmb();
-
- service = completion->service_userdata;
- user_service = service->base.userdata;
-@@ -903,7 +900,11 @@ vchiq_ioctl(struct file *file, unsigned
- break;
- }
-
-- instance->completion_remove++;
-+ /* Ensure that the above copy has completed
-+ ** before advancing the remove pointer. */
-+ mb();
-+
-+ instance->completion_remove = ++remove;
- }
-
- if (msgbufcount != args.msgbufcount) {
---- a/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_core.c
-+++ b/drivers/misc/vc04_services/interface/vchiq_arm/vchiq_core.c
-@@ -610,15 +610,15 @@ process_free_queue(VCHIQ_STATE_T *state)
- BITSET_T service_found[BITSET_SIZE(VCHIQ_MAX_SERVICES)];
- int slot_queue_available;
-
-- /* Use a read memory barrier to ensure that any state that may have
-- ** been modified by another thread is not masked by stale prefetched
-- ** values. */
-- rmb();
--
- /* Find slots which have been freed by the other side, and return them
- ** to the available queue. */
- slot_queue_available = state->slot_queue_available;
-
-+ /* Use a memory barrier to ensure that any state that may have been
-+ ** modified by another thread is not masked by stale prefetched
-+ ** values. */
-+ mb();
-+
- while (slot_queue_available != local->slot_queue_recycle) {
- unsigned int pos;
- int slot_index = local->slot_queue[slot_queue_available++ &
-@@ -626,6 +626,8 @@ process_free_queue(VCHIQ_STATE_T *state)
- char *data = (char *)SLOT_DATA_FROM_INDEX(state, slot_index);
- int data_found = 0;
-
-+ rmb();
-+
- vchiq_log_trace(vchiq_core_log_level, "%d: pfq %d=%x %x %x",
- state->id, slot_index, (unsigned int)data,
- local->slot_queue_recycle, slot_queue_available);
-@@ -741,6 +743,8 @@ process_free_queue(VCHIQ_STATE_T *state)
- up(&state->data_quota_event);
- }
-
-+ mb();
-+
- state->slot_queue_available = slot_queue_available;
- up(&state->slot_available_event);
- }
projects / openwrt / staging / yousong.git / blobdiff