[src/netbsd-8]: src/sys/kern Pull up following revision(s) (requested by hann...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/76dfb4ad5e65
branches:  netbsd-8
changeset: 988643:76dfb4ad5e65
user:      martin <martin%NetBSD.org@localhost>
date:      Fri Oct 08 14:59:59 2021 +0000

description:
Pull up following revision(s) (requested by hannken in ticket #1698):

        sys/kern/sys_pipe.c: revision 1.157

Fix a deadlock where one thread writes to a pipe, has more data
and no space in the pipe and waits on "pipe_wcv" while the reader
is closing the pipe and waits on "pipe_draincv".

Swap the test for "PIPE_EOF" and the "cv_wait_sig()" in "pipe_write()".

PR bin/56422 "zgrep -l sometimes hangs"

diffstat:

 sys/kern/sys_pipe.c |  15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diffs (43 lines):

diff -r 24543fb870e7 -r 76dfb4ad5e65 sys/kern/sys_pipe.c
--- a/sys/kern/sys_pipe.c       Thu Sep 23 10:08:35 2021 +0000
+++ b/sys/kern/sys_pipe.c       Fri Oct 08 14:59:59 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_pipe.c,v 1.140.12.1 2019/05/01 14:51:17 martin Exp $       */
+/*     $NetBSD: sys_pipe.c,v 1.140.12.2 2021/10/08 14:59:59 martin Exp $       */
 
 /*-
  * Copyright (c) 2003, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_pipe.c,v 1.140.12.1 2019/05/01 14:51:17 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_pipe.c,v 1.140.12.2 2021/10/08 14:59:59 martin Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1017,11 +1017,6 @@
                                break;
                        }
 
-                       pipeunlock(wpipe);
-                       error = cv_wait_sig(&wpipe->pipe_wcv, lock);
-                       (void)pipelock(wpipe, false);
-                       if (error != 0)
-                               break;
                        /*
                         * If read side wants to go away, we just issue a signal
                         * to ourselves.
@@ -1030,6 +1025,12 @@
                                error = EPIPE;
                                break;
                        }
+
+                       pipeunlock(wpipe);
+                       error = cv_wait_sig(&wpipe->pipe_wcv, lock);
+                       (void)pipelock(wpipe, false);
+                       if (error != 0)
+                               break;
                        wakeup_state = wpipe->pipe_state;
                }
        }