+ /* Notice that here we "up" the semaphore on which "to" is waiting, and
+ * below (the read) we wait on this semaphore (which is implemented by
+ * switch_pipe) and go sleeping. Thus, after that, we have resumed in
+ * "to", and can't use any more the value of "from" (which is outdated),
+ * nor the value in "to" (since it was the task which stole us the CPU,
+ * which we don't care about). */
+