nptl dependencies

.cvsignore

@@ -0,0 +1 @@
+config

INSTALL

@@ -21,6 +21,7 @@ if [ `uname` = Linux ]; then
 		echo "	NPTL not found."
 		echo "SYSVERSION=2.4" >$PLAN9/config
 	fi
+	rm -f ./a.out
 fi
 echo "Building mk..."
 cd src

lib/linux-isnptl.c

@@ -0,0 +1,15 @@
+#include <pthread.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int
+main(void)
+{
+	ulong x;
+
+	x = (ulong)pthread_self();
+	if(x < 1024*1024)
+		exit(1);	/* NOT NPTL */
+	exit(0);
+}

man/man1/install.1

@@ -40,7 +40,17 @@ can safely be repeated to rebuild the system from scratch.
 The system uses different threading implementations on Linux 2.6 and
 later kernels than on 2.4 and earlier;
 and on FreeBSD 5 and later kernels than on FreeBSD 4 and earlier.
-Running binaries from one class on another may not work.
+Running binaries from one class on another will not work.
+.PP
+Some Linux 2.6 systems (e.g., Gentoo) do not use the new NPTL pthread library
+even though the kernel supports them.  On these systems, plan9port must 
+fall back on the threading code intended for Linux 2.4.  To accomplish this,
+.I INSTALL
+checks whether the running system uses NPTL and sets
+.B SYSVERSION
+in
+.B \*9/config
+accordingly.
 .SH FILES
 .TP
 .B \*9/lib/moveplan9.files