Hello ! We have a xenomai application that uses mprotect to change write protection in order to set and clear breakpoint codes. This works quite well (the code invoking mprotect switches to linux, but thats ok). The problem is that from time to time the realtime task executing code in the area changed with mprotect also switches domains to handle a page fault. Is there some functionality in xenomai to change memory protection not using mprotect ? Attached you find a short sample that can reproduce this problem. Thanks Michael