allow config to override kernel version

INSTALL

@@ -3,7 +3,25 @@
 PLAN9=`pwd` export PLAN9
 PATH=$PLAN9/bin:$PATH export PATH
 
+echo "Resetting $PLAN9/config"
+rm -f $PLAN9/config
+
 (
+if [ `uname` = Linux ]; then
+	# On Linux, we use the kernel version to decide whether
+	# to use pthreads or not.  On 2.6 versions that aren't
+	# linking with NPTL by default, pretend to be an older kernel.
+	echo "Running on Linux: checking for NPTL..."
+	gcc lib/linux-isnptl.c
+	if ./a.out
+	then	
+		echo "	NPTL found."
+		echo "SYSVERSION=2.6" >$PLAN9/config
+	else
+		echo "	NPTL not found."
+		echo "SYSVERSION=2.4" >$PLAN9/config
+	fi
+fi
 echo "Building mk..."
 cd src
 make

src/libthread/pthread.c

@@ -133,6 +133,23 @@ _threadsetproc(Proc *p)
 void
 _pthreadinit(void)
 {
+	static struct utsname un;
+	pthread_t id;
+
+	if(uname(&un) < 0){
+		fprint(2, "warning: uname failed: %r\n");
+		goto Okay;
+	}
+	if(strcmp(un.sysname, "Linux") == 0){
+		/*
+		 * Want to distinguish between the old LinuxThreads pthreads
+		 * and the new NPTL implementation.  NPTL uses much bigger
+		 * thread IDs.
+		 */
+		id = pthread_self();
+		if(*(ulong*)&id < 1024*1024)
+			sysfatal("cannot use LinuxThreads as pthread library; see %s/src/libthread/README.Linux", get9root());
+	}
 	pthread_key_create(&prockey, 0);
 }
 

src/libthread/sysofiles.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
-tag="$OBJTYPE-$SYSNAME-`uname -r`-${CC9:-cc}"
+test -f $PLAN9/config && . $PLAN9/config
+
+tag="$OBJTYPE-$SYSNAME-${SYSVERSION:-`uname -r`}-${CC9:-cc}"
 case "$tag" in
 *-Linux-2.6.*)
 	echo pthread.o

src/libthread/threadimpl.h

@@ -6,6 +6,7 @@
 #include <sched.h>
 #include <signal.h>
 #include <ucontext.h>
+#include <sys/utsname.h>
 #include "libc.h"
 #include "thread.h"
 

src/mkhdr

@@ -7,8 +7,6 @@ OBJTYPE=`uname -m | sed '
 	s;ppc64;power;g;
 	s;ppc;power;g'`
 
-SYSVERSION=`uname -r`
-
 BIN=$PLAN9/bin
 LIBDIR=$PLAN9/lib