From: Phil Elwell <phil@xxxxxxxxxxxxxxx> One of points on the TODO list was to comment the memory barriers. This patch addresses the missing ones in order to help reviewers. Signed-off-by: Phil Elwell <phil@xxxxxxxxxxxxxxx> Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx> Link: https://github.com/raspberrypi/linux/pull/5066 --- .../vc04_services/interface/vchiq_arm/vchiq_arm.c | 4 ++++ .../vc04_services/interface/vchiq_arm/vchiq_core.c | 9 +++++++++ 2 files changed, 13 insertions(+) diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c index 3bcb893d14a1..dc33490ba7fb 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c @@ -602,6 +602,10 @@ static struct vchiq_arm_state *vchiq_platform_get_arm_state(struct vchiq_state * void remote_event_signal(struct remote_event *event) { + /* + * Ensure that all writes to shared data structures have completed + * before signalling the peer. + */ wmb(); event->fired = 1; diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c index 7b9c100eb74d..45ed30bfdbf5 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c @@ -528,6 +528,7 @@ remote_event_wait(wait_queue_head_t *wq, struct remote_event *event) return 0; } event->armed = 0; + /* Ensure that the peer sees that we are not waiting (armed == 0). */ wmb(); } @@ -650,6 +651,7 @@ request_poll(struct vchiq_state *state, struct vchiq_service *service, skip_service: state->poll_needed = 1; + /* Ensure the slot handler thread sees the poll_needed flag. */ wmb(); /* ... and ensure the slot handler runs. */ @@ -1156,6 +1158,7 @@ queue_message_sync(struct vchiq_state *state, struct vchiq_service *service, remote_event_wait(&state->sync_release_event, &local->sync_release); + /* Ensure that reads don't overtake the remote_event_wait. */ rmb(); header = (struct vchiq_header *)SLOT_DATA_FROM_INDEX(state, @@ -1959,6 +1962,7 @@ slot_handler_func(void *v) DEBUG_TRACE(SLOT_HANDLER_LINE); remote_event_wait(&state->trigger_event, &local->trigger); + /* Ensure that reads don't overtake the remote_event_wait. */ rmb(); DEBUG_TRACE(SLOT_HANDLER_LINE); @@ -2021,6 +2025,7 @@ sync_func(void *v) remote_event_wait(&state->sync_trigger_event, &local->sync_trigger); + /* Ensure that reads don't overtake the remote_event_wait. */ rmb(); msgid = header->msgid; @@ -3081,6 +3086,10 @@ enum vchiq_status vchiq_bulk_transfer(struct vchiq_instance *instance, unsigned if (vchiq_prepare_bulk_data(instance, bulk, offset, uoffset, size, dir)) goto unlock_error_exit; + /* + * Ensure that the bulk data record is visible to the peer + * before proceeding. + */ wmb(); vchiq_log_info(vchiq_core_log_level, "%d: bt (%d->%d) %cx %x@%pad %pK", -- 2.25.1
