Quoting Sagar Arun Kamble (2018-01-23 15:42:17)
> static void *guc_get_write_buffer(struct intel_guc *guc)
> {
> - if (!guc->log.runtime.relay_chan)
> + if (!guc_log_has_relay(guc))
> return NULL;
>
> /* Just get the base address of a new sub buffer and copy data into it
> @@ -266,7 +276,9 @@ static void guc_read_update_log_buffer(struct intel_guc *guc)
> log_buf_state = src_data = guc->log.runtime.buf_addr;
>
> /* Get the pointer to local buffer to store the logs */
> + mutex_lock(&guc->log.runtime.relay_lock);
> log_buf_snapshot_state = dst_data = guc_get_write_buffer(guc);
> + mutex_unlock(&guc->log.runtime.relay_lock);
Since dst_data/log_buf_snapshot_state are pointing into the relay_chan
they are only valid underneath the relay_lock (we don't have any
references or whatnot).
> /* Actual logs are present from the 2nd page */
> src_data += PAGE_SIZE;
> @@ -335,6 +347,7 @@ static void guc_read_update_log_buffer(struct intel_guc *guc)
> dst_data += buffer_size;
> }
>
> + mutex_lock(&guc->log.runtime.relay_lock);
> if (log_buf_snapshot_state)
> guc_move_to_next_buf(guc);
> else {
> @@ -344,6 +357,7 @@ static void guc_read_update_log_buffer(struct intel_guc *guc)
> DRM_ERROR_RATELIMITED("no sub-buffer to capture logs\n");
> guc->log.capture_miss_count++;
> }
> + mutex_unlock(&guc->log.runtime.relay_lock);
I.e. it's no good just reacquiring the lock as the state may have
perished in between.
-Chris
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