- spin_lock(&ctx->switch_log->lock);
- if (ctx->switch_log->head == ctx->switch_log->tail) {
- /* multiple readers race? */
- spin_unlock(&ctx->switch_log->lock);
- continue;
+ } else {
+ /* spufs_wait will drop the mutex and
+ * re-acquire, but since we're in read(), the
+ * file cannot be _released (and so
+ * ctx->switch_log is stable).
+ */
+ error = spufs_wait(ctx->switch_log->wait,
+ spufs_switch_log_used(ctx) > 0);
+
+ /* On error, spufs_wait returns without the
+ * state mutex held */
+ if (error)
+ return error;
+
+ /* We may have had entries read from underneath
+ * us while we dropped the mutex in spufs_wait,
+ * so re-check */
+ if (spufs_switch_log_used(ctx) == 0)
+ continue;
+ }