[Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
Improve the configure test for presence of ucontext functions by
making linker warnings fatal; this allows us to detect when we are
linked with a glibc which implements makecontext() to always return
ENOSYS.
Signed-off-by: Peter Maydell peter.mayd...@linaro.org
---
Compiling on an Ubuntu Natty ARM host will hit this.
(Anybody think we should clean up our configure tests so we can
enable -Werror and -Wl,--fatal-warnings on all of them?)
configure |7 +--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/configure b/configure
index 9b4fe34..4d9d9e0 100755
--- a/configure
+++ b/configure
@@ -2549,9 +2549,12 @@ ucontext_coroutine=no
if test $darwin != yes; then
cat $TMPC EOF
#include ucontext.h
-int main(void) { makecontext(0, 0, 0); }
+int main(void) { makecontext(0, 0, 0); return 0; }
EOF
- if compile_prog ; then
+ # Note that we enable fatal linker warnings to catch the
+ # glibc makecontext is not implemented and will always fail
+ # linker warning.
+ if compile_prog -Wl,--fatal-warnings ; then
ucontext_coroutine=yes
fi
fi
--
1.7.4.1
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
On 23 February 2012 16:16, Peter Maydell peter.mayd...@linaro.org wrote: Improve the configure test for presence of ucontext functions by making linker warnings fatal; this allows us to detect when we are linked with a glibc which implements makecontext() to always return ENOSYS. Er, ignore this, emailed wrong patch by mistake! -- PMM
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
On 13 October 2011 23:23, Andreas Färber andreas.faer...@web.de wrote: Am 13.10.2011 16:26, schrieb Andreas Färber: Am 12.10.2011 18:21, schrieb Peter Maydell: Improve the configure test for presence of ucontext functions by making linker warnings fatal; this allows us to detect when we are linked with a glibc which implements makecontext() to always return ENOSYS. --- Compiling on an Ubuntu Natty ARM host will hit this. Works on Ubuntu Maverick ARM host as well. Erm... This works great, also for accept4(), on Linux, but it's not portable. Apple ld(1) doesn't seem to have --fatal-warnings. I've also just discovered that it's no use on Oneiric, where the linker warning has gone away but the syscall still always returns ENOSYS. I think we should just always use the gthread implementation rather than preferring a non-portable-and-hard-to-detect set of functions (which increases the set of different configs we need to test with). If there's a performance problem with that we should get it fixed in gthread :-) -- PMM
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
On 10/14/2011 02:30 PM, Peter Maydell wrote: I've also just discovered that it's no use on Oneiric, where the linker warning has gone away but the syscall still always returns ENOSYS. I think we should just always use the gthread implementation rather than preferring a non-portable-and-hard-to-detect set of functions (which increases the set of different configs we need to test with). If there's a performance problem with that we should get it fixed in gthread:-) A user-space longjmp will always be slower than a mutex+condvar+context switch. We're talking _orders of magnitude_ slower. At this point it's better to write assembly, since we already support only a dozen TCG targets. I played with an alternative implementation using a 2-barrier instead of mutex+condvar, but it didn't give any speedup and was still much slower than gthread. Paolo
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
On 10/14/2011 02:47 PM, Paolo Bonzini wrote: A user-space longjmp will always be slower than a mutex+condvar+context switch. Gah, I obviously meant faster. :) Paolo
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
On 14 October 2011 13:55, Paolo Bonzini pbonz...@redhat.com wrote: On 10/14/2011 02:47 PM, Paolo Bonzini wrote: A user-space longjmp will always be slower than a mutex+condvar+context switch. Gah, I obviously meant faster. :) Ah, I hadn't actually looked at the coroutine-gthread.c code, and had assumed it was implementing coroutines via a gthread coroutine abstraction rather than via gthread real actual threads. -- PMM
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
Am 12.10.2011 18:21, schrieb Peter Maydell:
Improve the configure test for presence of ucontext functions by
making linker warnings fatal; this allows us to detect when we are
linked with a glibc which implements makecontext() to always return
ENOSYS.
Signed-off-by: Peter Maydellpeter.mayd...@linaro.org
Tested-by: Andreas Färber afaer...@suse.de
---
Compiling on an Ubuntu Natty ARM host will hit this.
Works on Ubuntu Maverick ARM host as well.
(Anybody think we should clean up our configure tests so we can
enable -Werror and -Wl,--fatal-warnings on all of them?)
In theory that would be nice. I noticed for example that a missing
glib2-devel package is not caught by configure, on openSUSE.
As a start for cleaning up...
configure |7 +--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/configure b/configure
index 9b4fe34..4d9d9e0 100755
--- a/configure
+++ b/configure
@@ -2549,9 +2549,12 @@ ucontext_coroutine=no
if test $darwin != yes; then
cat $TMPC EOF
#includeucontext.h
-int main(void) { makecontext(0, 0, 0); }
+int main(void) { makecontext(0, 0, 0); return 0; }
...we could give a good example by adopting regular multi-line Coding
Style, like accept4() and others.
Andreas
EOF
- if compile_prog ; then
+ # Note that we enable fatal linker warnings to catch the
+ # glibc makecontext is not implemented and will always fail
+ # linker warning.
+ if compile_prog -Wl,--fatal-warnings ; then
ucontext_coroutine=yes
fi
fi
--
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746, AG Nürnberg
Re: [Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
Am 13.10.2011 16:26, schrieb Andreas Färber: Am 12.10.2011 18:21, schrieb Peter Maydell: Improve the configure test for presence of ucontext functions by making linker warnings fatal; this allows us to detect when we are linked with a glibc which implements makecontext() to always return ENOSYS. Signed-off-by: Peter Maydellpeter.mayd...@linaro.org Tested-by: Andreas Färber afaer...@suse.de --- Compiling on an Ubuntu Natty ARM host will hit this. Works on Ubuntu Maverick ARM host as well. Erm... This works great, also for accept4(), on Linux, but it's not portable. Apple ld(1) doesn't seem to have --fatal-warnings. http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/Xcode-3.2.5/man1/ld.1.html Sun/Oracle ld(1) does seem to have it as alias to -z fatal-warnings. http://download.oracle.com/docs/cd/E19963-01/html/821-1461/ld-1.html So, we'd have to check for valid linker options first? Andreas
[Qemu-devel] [PATCH] configure: Detect when glibc implements makecontext() to always fail
Improve the configure test for presence of ucontext functions by
making linker warnings fatal; this allows us to detect when we are
linked with a glibc which implements makecontext() to always return
ENOSYS.
Signed-off-by: Peter Maydell peter.mayd...@linaro.org
---
Compiling on an Ubuntu Natty ARM host will hit this.
(Anybody think we should clean up our configure tests so we can
enable -Werror and -Wl,--fatal-warnings on all of them?)
configure |7 +--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/configure b/configure
index 9b4fe34..4d9d9e0 100755
--- a/configure
+++ b/configure
@@ -2549,9 +2549,12 @@ ucontext_coroutine=no
if test $darwin != yes; then
cat $TMPC EOF
#include ucontext.h
-int main(void) { makecontext(0, 0, 0); }
+int main(void) { makecontext(0, 0, 0); return 0; }
EOF
- if compile_prog ; then
+ # Note that we enable fatal linker warnings to catch the
+ # glibc makecontext is not implemented and will always fail
+ # linker warning.
+ if compile_prog -Wl,--fatal-warnings ; then
ucontext_coroutine=yes
fi
fi
--
1.7.4.1
