From: Jeff Law <law@redhat.com>
To: Szabolcs Nagy <szabolcs.nagy@arm.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: Marcus Shawcroft <Marcus.Shawcroft@arm.com>
Subject: Re: [PATCH, PR67627][RFC] broken libatomic multilib parallel build
Date: Wed, 16 Dec 2015 17:05:00 -0000 [thread overview]
Message-ID: <567199C1.1020100@redhat.com> (raw)
In-Reply-To: <56618964.3020209@arm.com>
On 12/04/2015 05:39 AM, Szabolcs Nagy wrote:
> As described in pr other/67627, the all-multi target can be
> built in parallel with the %_.lo targets which generate make
> dependencies that are parsed during the build of all-multi.
>
> gcc -MD does not generate the makefile dependencies in an
> atomic way so make can fail if it concurrently parses those
> half-written files.
> (not observed on x86, but happens on arm native builds.)
>
> this workaround forces all-multi to only run after the *_.lo
> targets are done, but there might be a better solution using
> automake properly. (automake should know about the generated
> make dependency files that are included into the makefile so
> no manual tinkering is needed to get the right build order,
> but i don't know how to do that.)
>
> 2015-12-04 Szabolcs Nagy <szabolcs.nagy@arm.com>
>
> PR other/67627
> * Makefile.am (all-multi): Add dependency.
> * Makefile.in: Regenerate.
ISTM that many of the libraries have this problem.
[law@localhost gcc]$ grep all-am: */Makefile.in | grep -v install
boehm-gc/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi
gotools/Makefile.in:all-am: Makefile $(PROGRAMS) $(MANS)
libatomic/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi
auto-config.h
libbacktrace/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi config.h
libcc1/Makefile.in:all-am: Makefile $(LTLIBRARIES) cc1plugin-config.h
libcilkrts/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi $(HEADERS)
libffi/Makefile.in:all-am: Makefile $(INFO_DEPS) $(LTLIBRARIES)
all-multi $(DATA) \
libgfortran/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi
$(DATA) $(HEADERS) config.h
libgo/Makefile.in:all-am: Makefile $(LIBRARIES) $(LTLIBRARIES) all-multi
$(DATA) \
libgomp/Makefile.in:all-am: Makefile $(INFO_DEPS) $(LTLIBRARIES)
all-multi $(HEADERS) \
libitm/Makefile.in:all-am: Makefile $(INFO_DEPS) $(LTLIBRARIES)
all-multi $(HEADERS) \
libjava/Makefile.in:all-am: Makefile $(LTLIBRARIES) $(PROGRAMS)
$(SCRIPTS) all-multi \
libmpx/Makefile.in:all-am: Makefile all-multi $(HEADERS) config.h
liboffloadmic/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi
$(HEADERS) all-local
libquadmath/Makefile.in:all-am: Makefile $(INFO_DEPS) $(LTLIBRARIES)
all-multi $(HEADERS) \
libsanitizer/Makefile.in:all-am: Makefile all-multi $(HEADERS) config.h
libssp/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi $(HEADERS)
config.h
libstdc++-v3/Makefile.in:all-am: Makefile all-multi config.h
libvtv/Makefile.in:all-am: Makefile $(LTLIBRARIES) all-multi $(HEADERS)
lto-plugin/Makefile.in:all-am: Makefile $(LTLIBRARIES) config.h all-local
zlib/Makefile.in:all-am: Makefile $(LIBRARIES) $(LTLIBRARIES) all-multi
And if you look at the all-multi targets in each of those, all-multi has
no dependencies. So any of them which use auto-dependency generation
are potentially going to bump into this problem.
We can't fix it by twiddling Makefile.in as that's a generated file. I
think it has to happen at the automake level.
jeff
next prev parent reply other threads:[~2015-12-16 17:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-04 12:39 Szabolcs Nagy
2015-12-11 11:44 ` Szabolcs Nagy
2015-12-16 17:05 ` Jeff Law [this message]
2015-12-16 17:06 ` Jeff Law
2015-12-17 9:51 ` Szabolcs Nagy
2016-01-05 18:05 ` Jeff Law
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