hurd: Document how EINTR should be handled in critical sections

	* hurd/hurd/signal.h (_hurd_critical_section_lock): Document how EINTR
	should be handled.

1 files changed, 7 insertions, 1 deletions

diff --git a/hurd/hurd/signal.h b/hurd/hurd/signal.h
index c30f536436..b0b53668d2 100644
--- a/hurd/hurd/signal.h
+++ b/hurd/hurd/signal.h
@@ -168,7 +168,13 @@ extern int _hurd_core_limit;
    A critical section is a section of code which cannot safely be interrupted
    to run a signal handler; for example, code that holds any lock cannot be
    interrupted lest the signal handler try to take the same lock and
-   deadlock result.  */
+   deadlock result.
+
+   As a consequence, a critical section will see its RPCs return EINTR, even if
+   SA_RESTART is set!  In that case, the critical section should be left, so
+   that the handler can run, and the whole critical section be tried again, to
+   avoid unexpectingly exposing EINTR to the application.
+   */
 
 extern void *_hurd_critical_section_lock (void);