signal.7: Add reference to seccomp_unotify(2)

The seccomp user-space notification feature can cause changes in
the semantics of SA_RESTART with respect to system calls that
would never normally be restarted. Point the reader to the page
that provide further details.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/signal.7 b/man7/signal.7
index 29c160fa2671816edd20161a2dd12f82ef7886a1..bc315560558270c637ec5c96fe6782c9828a8394 100644 (file)
--- a/man7/signal.7
+++ b/man7/signal.7
@@ -857,6 +857,15 @@ The
 .BR sleep (3)
 function is also never restarted if interrupted by a handler,
 but gives a success return: the number of seconds remaining to sleep.
+.PP
+In certain circumstances, the
+.BR seccomp (2)
+user-space notification feature can lead to restarting of system calls
+that would otherwise never be restarted by
+.BR SA_RESTART ;
+for details, see
+.BR seccomp_unotify (2).
+.\"
 .SS Interruption of system calls and library functions by stop signals
 On Linux, even in the absence of signal handlers,
 certain blocking interfaces can fail with the error