7420 signalfd deadlock on pollwakeup

7421 panic in signalfd
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Gordon Ross <gwr@nexenta.com>

1 files changed, 19 insertions, 3 deletions

diff --git a/usr/src/man/man3c/signalfd.3c b/usr/src/man/man3c/signalfd.3c
index ad7bafca1a..f08e85b273 100644
--- a/usr/src/man/man3c/signalfd.3c
+++ b/usr/src/man/man3c/signalfd.3c
@@ -8,9 +8,9 @@
 .\"  source.  A copy of the CDDL is also available via the Internet at
 .\"  http://www.illumos.org/license/CDDL.
 .\"
-.\"  Copyright 2015, Joyent, Inc.
+.\"  Copyright 2016, Joyent, Inc.
 .\"
-.Dd "April 9, 2016"
+.Dd "May 05, 2016"
 .Dt SIGNALFD 3C
 .Os
 .Sh NAME
@@ -150,6 +150,20 @@ typedef struct signalfd_siginfo {
         uint8_t  ssi_pad[48];   /* pad size to 128 bytes */
 } signalfd_siginfo_t;
 .Ed
+.Sh NOTES
+File descriptor duplication during fork presents a challenge to the
+.Sy signalfd
+facility since signal data and events are dependent on the process from which
+they are queried.  Its use with caching event systems such as
+.Xr epoll 5 ,
+.Sy /dev/poll ,
+or
+.Xr port_create 3C
+can result in undefined behavior if signalfd and polling descriptors are used
+together after being shared across a fork.  Such restrictions do not apply if
+the child only calls
+.Xr close 2
+on the descriptors.
 .Sh RETURN VALUES
 Upon successful completion, a file descriptor associated with the instance
 is returned. Otherwise, -1 is returned and errno is set to indicate the error.
@@ -187,6 +201,8 @@ Unable to allocate state for the file descriptor.
 .Sh SEE ALSO
 .Xr poll 2 ,
 .Xr sigwait 2 ,
+.Xr port_create 3C ,
 .Xr sigsetops 3C ,
 .Xr sigwaitinfo 3C ,
-.Xr signal.h 3HEAD
+.Xr signal.h 3HEAD ,
+.Xr epoll 5