[master] enable threads by default

3572.	[func]		Threads are now enabled by default on most
			operating systems. [RT #25483]

CHANGES

+3572.	[func]		Threads are now enabled by default on most
+			operating systems. [RT #25483]
+
 3571.	[bug]		Address race condition in dns_client_startresolve().
 			[RT #33234]
 

README

@@ -237,6 +237,18 @@ Building
             BUILD_LDFLAGS (optional)
             BUILD_LIBS (optional)
 
+        On most platforms, BIND 9 is built with multithreading
+        support, allowing it to take advantage of multiple CPUs.
+        You can configure this by specifying "--enable-threads" or
+        "--disable-threads" on the configure command line.  The default
+        is to enable threads, except on some older operating systems
+        on which threads are known to have had problems in the past.
+        (Note: Prior to BIND 9.10, the default was to disable threads on
+        Linux systems; this has been reversed.  On Linux systems, the
+        threaded build is known to change BIND's behavior with respect
+        to file permissions; it may be necessary to specify a user with
+        the -u option when running named.)
+
         To build shared libraries, specify "--with-libtool" on the
         configure command line.
 
@@ -257,13 +269,6 @@ Building
         file support to handle files bigger than 2GB.  This can be
         done by "--enable-largefile" on the configure command line.
 
-        On some platforms, BIND 9 can be built with multithreading
-        support, allowing it to take advantage of multiple CPUs.
-        You can specify whether to build a multithreaded BIND 9
-        by specifying "--enable-threads" or "--disable-threads"
-        on the configure command line.  The default is operating
-        system dependent.
-
         Support for the "fixed" rrset-order option can be enabled
         or disabled by specifying "--enable-fixed-rrset" or
         "--disable-fixed-rrset" on the configure command line.

config.threads.in

@@ -56,16 +56,13 @@ case $host in
 *-bsdi5*)
 	use_threads=true ;;
 *-linux*)
-   	# Threads are disabled on Linux by default because most
-	# Linux kernels produce unusable core dumps from multithreaded
-	# programs, and because of limitations in setuid().
-	use_threads=false ;;	
+	use_threads=true ;;	
 *-darwin[[123456789]].*)
 	use_threads=false ;;
 *-darwin*.*)
 	use_threads=true ;;
 *)
-	use_threads=false ;;
+	use_threads=true ;;
 esac
 
 AC_ARG_ENABLE(threads,

configure

@@ -15116,16 +15116,13 @@ case $host in
 *-bsdi5*)
 	use_threads=true ;;
 *-linux*)
-   	# Threads are disabled on Linux by default because most
-	# Linux kernels produce unusable core dumps from multithreaded
-	# programs, and because of limitations in setuid().
-	use_threads=false ;;
+	use_threads=true ;;
 *-darwin[123456789].*)
 	use_threads=false ;;
 *-darwin*.*)
 	use_threads=true ;;
 *)
-	use_threads=false ;;
+	use_threads=true ;;
 esac
 
 # Check whether --enable-threads was given.