Since GNU Make doesn't support anything like the .MUTEX directive
(http://savannah.gnu.org/bugs/?func=detailitem&item_id=17873), and
accidentally doing "make -j8 -l4" makes my laptop useless for several
minutes while it tries to link all the front ends at once, I decided to
kludge a workaround.
This hack uses mkdir as a locking mechanism, as it fails if the
directory already exists. Each front-end rule first tries to get the
lock, and spins if the lock isn't available. Currently I'm enabling the
locking by default on build hosts with less than 8GB of memory.
Releasing the lock is not reliable; if the user interrupts the link with
^C, the lock will remain. So I adjusted 'make all' to remove the lock
early on, though that only works for the typical case, and users that do
something like 'make cc1plus' could still run into trouble.
Thoughts? Is this too horrible a hack, or does it seem like something
we might want?
Maybe I should fix Make instead.
Jason
commit 47980ab5ea7f1037b8b7cce9b8abfe1c0a75c032
Author: Jason Merrill <ja...@redhat.com>
Date: Thu Apr 25 17:54:17 2013 -0400
* Makefile.in (link-mutex, remove-link-mutex): New targets.
(native, mostlyclean): Remove link mutex.
* configure.ac: Handle --enable-link-mutex.
* */Make-lang.in: Use link mutex.
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 903125e..3934e16 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1737,8 +1737,8 @@ start.encap: native xgcc$(exeext) cpp$(exeext) specs \
rest.encap: lang.rest.encap
# This is what is made with the host's compiler
# whether making a cross compiler or not.
-native: config.status auto-host.h build-@POSUB@ $(LANGUAGES) \
- $(EXTRA_PROGRAMS) $(COLLECT2) lto-wrapper$(exeext) \
+native: remove-link-mutex config.status auto-host.h build-@POSUB@ \
+ $(LANGUAGES) $(EXTRA_PROGRAMS) $(COLLECT2) lto-wrapper$(exeext) \
gcc-ar$(exeext) gcc-nm$(exeext) gcc-ranlib$(exeext)
ifeq ($(enable_plugin),yes)
@@ -4529,6 +4529,8 @@ mostlyclean: lang.mostlyclean
-rm -f gtype.state
# Delete genchecksum outputs
-rm -f *-checksum.c
+# Delete front-end linking mutex directory
+ -rm -rf link-mutex
# Delete all files made by compilation
# that don't exist in the distribution.
@@ -5335,3 +5337,14 @@ po/gcc.pot: force
$(MAKE) srcextra
AWK=$(AWK) $(SHELL) $(srcdir)/po/exgettext \
$(XGETTEXT) gcc $(srcdir)
+
+do_link_mutex = @DO_LINK_MUTEX@
+.PHONY: link-mutex
+link-mutex:
+ifeq ($(do_link_mutex),true)
+ while ! mkdir link-mutex 2>/dev/null; do sleep 1; done
+endif
+
+.PHONY: remove-link-mutex
+remove-link-mutex:
+ -rm -rf link-mutex
diff --git a/gcc/ada/gcc-interface/Make-lang.in b/gcc/ada/gcc-interface/Make-lang.in
index ef12b4b..7d88961 100644
--- a/gcc/ada/gcc-interface/Make-lang.in
+++ b/gcc/ada/gcc-interface/Make-lang.in
@@ -562,7 +562,10 @@ TARGET_ADA_SRCS =
# Since the RTL should be built with the latest compiler, remove the
# stamp target in the parent directory whenever gnat1 is rebuilt
gnat1$(exeext): $(TARGET_ADA_SRCS) $(GNAT1_OBJS) $(ADA_BACKEND) libcommon-target.a $(LIBDEPS)
- +$(GCC_LINK) -o $@ $(GNAT1_OBJS) $(ADA_BACKEND) libcommon-target.a $(LIBS) $(SYSLIBS) $(BACKENDLIBS) $(CFLAGS)
+ $(MAKE) link-mutex
+ +$(GCC_LINK) -o $@ $(GNAT1_OBJS) $(ADA_BACKEND) \
+ libcommon-target.a $(LIBS) $(SYSLIBS) $(BACKENDLIBS) $(CFLAGS); \
+ $(MAKE) remove-link-mutex
$(RM) stamp-gnatlib2-rts stamp-tools
gnatbind$(exeext): ada/b_gnatb.o $(CONFIG_H) $(GNATBIND_OBJS) ggc-none.o libcommon-target.a $(LIBDEPS)
diff --git a/gcc/c/Make-lang.in b/gcc/c/Make-lang.in
index 8310e0a..cf61d74 100644
--- a/gcc/c/Make-lang.in
+++ b/gcc/c/Make-lang.in
@@ -75,8 +75,10 @@ cc1-checksum.c : build/genchecksum$(build_exeext) checksum-options \
cc1-checksum.o : cc1-checksum.c $(CONFIG_H) $(SYSTEM_H)
cc1$(exeext): $(C_OBJS) cc1-checksum.o $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ $(C_OBJS) \
- cc1-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS)
+ cc1-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
#
# Build hooks:
diff --git a/gcc/configure b/gcc/configure
index fd4a0eb..ab56d21 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -670,6 +670,7 @@ subdirs
dollar
gcc_tooldir
enable_lto
+DO_LINK_MUTEX
MAINT
zlibinc
zlibdir
@@ -916,6 +917,7 @@ with_long_double_128
with_gc
with_system_zlib
enable_maintainer_mode
+enable_link_mutex
enable_version_specific_runtime_libs
enable_plugin
enable_libquadmath_support
@@ -1627,6 +1629,8 @@ Optional Features:
--enable-maintainer-mode
enable make rules and dependencies not useful (and
sometimes confusing) to the casual installer
+ --enable-link-mutex avoid linking multiple front-ends at once to avoid
+ thrashing on the build machine
--enable-version-specific-runtime-libs
specify that runtime libraries should be installed
in a compiler-specific directory
@@ -17830,7 +17834,7 @@ else
lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
lt_status=$lt_dlunknown
cat > conftest.$ac_ext <<_LT_EOF
-#line 17833 "configure"
+#line 17837 "configure"
#include "confdefs.h"
#if HAVE_DLFCN_H
@@ -17936,7 +17940,7 @@ else
lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
lt_status=$lt_dlunknown
cat > conftest.$ac_ext <<_LT_EOF
-#line 17939 "configure"
+#line 17943 "configure"
#include "confdefs.h"
#if HAVE_DLFCN_H
@@ -27041,6 +27045,32 @@ else
MAINT='#'
fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to avoid linking multiple front-ends at once" >&5
+$as_echo_n "checking whether to avoid linking multiple front-ends at once... " >&6; }
+ # Check whether --enable-link-mutex was given.
+if test "${enable_link_mutex+set}" = set; then :
+ enableval=$enable_link_mutex; do_link_mutex=$enableval
+else
+ # By default avoid simultaneous links on machines with less than 8GB.
+ mem="$(free|sed -n 2p|awk '{print $2}')" 2>/dev/null
+ if test "$mem" -lt 8000000 2>/dev/null; then
+ do_link_mutex=yes
+ else
+ do_link_mutex=no
+ fi
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $do_link_mutex" >&5
+$as_echo "$do_link_mutex" >&6; }
+
+if test "$do_link_mutex" = "yes"; then
+ DO_LINK_MUTEX=true
+else
+ DO_LINK_MUTEX=false
+fi
+
+
# --------------
# Language hooks
# --------------
diff --git a/gcc/configure.ac b/gcc/configure.ac
index a859d99..71f8e31 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -4938,6 +4938,30 @@ else
fi
AC_SUBST(MAINT)dnl
+dnl Whether to prevent multiple front-ends from linking at the same time
+
+AC_MSG_CHECKING([whether to avoid linking multiple front-ends at once])
+ AC_ARG_ENABLE(link-mutex,
+[AS_HELP_STRING([--enable-link-mutex],
+ [avoid linking multiple front-ends at once to avoid thrashing
+ on the build machine])],
+ do_link_mutex=$enableval,
+ # By default avoid simultaneous links on machines with less than 8GB.
+ mem="$(free|sed -n 2p|awk '{print $2}')" 2>/dev/null
+ if test "$mem" -lt 8000000 2>/dev/null; then
+ do_link_mutex=yes
+ else
+ do_link_mutex=no
+ fi)
+AC_MSG_RESULT($do_link_mutex)
+
+if test "$do_link_mutex" = "yes"; then
+ DO_LINK_MUTEX=true
+else
+ DO_LINK_MUTEX=false
+fi
+AC_SUBST(DO_LINK_MUTEX)
+
# --------------
# Language hooks
# --------------
diff --git a/gcc/cp/Make-lang.in b/gcc/cp/Make-lang.in
index cda4897..760d801 100644
--- a/gcc/cp/Make-lang.in
+++ b/gcc/cp/Make-lang.in
@@ -100,8 +100,10 @@ cc1plus-checksum.c : build/genchecksum$(build_exeext) checksum-options \
cc1plus-checksum.o : cc1plus-checksum.c $(CONFIG_H) $(SYSTEM_H)
cc1plus$(exeext): $(CXX_OBJS) cc1plus-checksum.o $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
- $(CXX_OBJS) cc1plus-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS)
+ $(CXX_OBJS) cc1plus-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
ifeq ($(ENABLE_MAINTAINER_RULES), true)
# Special build rule. This is a maintainer rule, that is only
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 1265129..89b8260 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1293,6 +1293,11 @@ opposite effect. If neither option is specified, the configure script
will try to guess whether the @code{.init_array} and
@code{.fini_array} sections are supported and, if they are, use them.
+@item --enable-link-mutex
+When building GCC, use a mutex to avoid linking the compilers for
+multiple languages at the same time, to avoid thrashing. By default,
+this is enabled if the build machine has less than 8GB of memory.
+
@item --enable-maintainer-mode
The build rules that regenerate the Autoconf and Automake output files as
well as the GCC master message catalog @file{gcc.pot} are normally
diff --git a/gcc/fortran/Make-lang.in b/gcc/fortran/Make-lang.in
index c3f826c..2c8bcac 100644
--- a/gcc/fortran/Make-lang.in
+++ b/gcc/fortran/Make-lang.in
@@ -98,9 +98,10 @@ gfortran-cross$(exeext): gfortran$(exeext)
# The compiler itself is called f951.
f951$(exeext): $(F95_OBJS) \
$(BACKEND) $(LIBDEPS) attribs.o
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
$(F95_OBJS) $(BACKEND) $(ZLIB) $(LIBS) attribs.o \
- $(BACKENDLIBS)
+ $(BACKENDLIBS); $(MAKE) remove-link-mutex
gt-fortran-trans.h : s-gtype; @true
#
diff --git a/gcc/go/Make-lang.in b/gcc/go/Make-lang.in
index dd98080..7059672 100644
--- a/gcc/go/Make-lang.in
+++ b/gcc/go/Make-lang.in
@@ -76,8 +76,10 @@ GO_OBJS = \
go/unsafe.o
go1$(exeext): $(GO_OBJS) attribs.o $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(CXX) $(ALL_CXXFLAGS) $(LDFLAGS) -o $@ \
- $(GO_OBJS) attribs.o $(BACKEND) $(LIBS) $(BACKENDLIBS)
+ $(GO_OBJS) attribs.o $(BACKEND) $(LIBS) $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
# Documentation.
diff --git a/gcc/java/Make-lang.in b/gcc/java/Make-lang.in
index 7ed3220..c1d7f5c 100644
--- a/gcc/java/Make-lang.in
+++ b/gcc/java/Make-lang.in
@@ -99,8 +99,10 @@ jvspec.o-warn = -Wno-error
jc1$(exeext): $(JAVA_OBJS) $(BACKEND) $(LIBDEPS) attribs.o
rm -f $@
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
- $(JAVA_OBJS) $(BACKEND) $(ZLIB) $(LIBICONV) $(LIBS) attribs.o $(BACKENDLIBS)
+ $(JAVA_OBJS) $(BACKEND) $(ZLIB) $(LIBICONV) $(LIBS) attribs.o $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
jcf-dump$(exeext): $(JCFDUMP_OBJS) $(LIBDEPS)
rm -f $@
diff --git a/gcc/lto/Make-lang.in b/gcc/lto/Make-lang.in
index a0bdc26..b73b3d4 100644
--- a/gcc/lto/Make-lang.in
+++ b/gcc/lto/Make-lang.in
@@ -71,8 +71,10 @@ lto.stagefeedback:
lto-warn = $(STRICT_WARN)
$(LTO_EXE): $(LTO_OBJS) $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
- $(LTO_OBJS) $(BACKEND) $(BACKENDLIBS) $(LIBS)
+ $(LTO_OBJS) $(BACKEND) $(BACKENDLIBS) $(LIBS); \
+ $(MAKE) remove-link-mutex
# Dependencies
lto/lto-lang.o: lto/lto-lang.c $(CONFIG_H) coretypes.h debug.h \
diff --git a/gcc/objc/Make-lang.in b/gcc/objc/Make-lang.in
index 9e005c1..f45d567 100644
--- a/gcc/objc/Make-lang.in
+++ b/gcc/objc/Make-lang.in
@@ -68,9 +68,11 @@ cc1obj-checksum.c : build/genchecksum$(build_exeext) checksum-options \
cc1obj-checksum.o : cc1obj-checksum.c $(CONFIG_H) $(SYSTEM_H)
cc1obj$(exeext): $(OBJC_OBJS) $(C_AND_OBJC_OBJS) cc1obj-checksum.o $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
$(OBJC_OBJS) $(C_AND_OBJC_OBJS) cc1obj-checksum.o \
- $(BACKEND) $(LIBS) $(BACKENDLIBS)
+ $(BACKEND) $(LIBS) $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
# Objective C language specific files.
diff --git a/gcc/objcp/Make-lang.in b/gcc/objcp/Make-lang.in
index 731ca9e..bd84b5f 100644
--- a/gcc/objcp/Make-lang.in
+++ b/gcc/objcp/Make-lang.in
@@ -72,8 +72,10 @@ cc1objplus-checksum.c : build/genchecksum$(build_exeext) checksum-options \
cc1objplus-checksum.o : cc1objplus-checksum.c $(CONFIG_H) $(SYSTEM_H)
cc1objplus$(exeext): $(OBJCXX_OBJS) cc1objplus-checksum.o $(BACKEND) $(LIBDEPS)
+ $(MAKE) link-mutex
+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
- $(OBJCXX_OBJS) cc1objplus-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS)
+ $(OBJCXX_OBJS) cc1objplus-checksum.o $(BACKEND) $(LIBS) $(BACKENDLIBS); \
+ $(MAKE) remove-link-mutex
# Objective C++ language specific files.
