| Message ID | 20230912194751.GB3415652@frogsfrogsfrogs (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
On Tue, Sep 12, 2023 at 12:47:51PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > xfsprogs during compilation tries to detect if liburcu supports atomic > 64-bit ops on the platform it is being compiled on, and if not it falls > back to using pthread mutex locks. > > The detection logic for that fallback relies on _uatomic_link_error() > which is a link-time trick used by liburcu that will cause compilation > errors on archs that lack the required support. That only works for the > generic liburcu code though, and it is not implemented for the > x86-specific code. > > In practice this means that when xfsprogs is compiled on 32-bit x86 > archs will successfully link to liburcu for atomic ops, but liburcu does > not support atomic64_t on those archs. It indicates this during runtime > by generating an illegal instruction that aborts execution, and thus > causes various xfsprogs utils to be segfaulting. > > Fix this by requiring that unsigned longs are at least 64 bits in size, > which /usually/ means that 64-bit atomic counters are supported. We > can't simply execute the liburcu atomic64_t detection code during > configure instead of only relying on the linker error because that > doesn't work for cross-compiled packages. > > Fixes: 7448af588a2e ("libxfs: fix atomic64_t poorly for 32-bit architectures") > Reported-by: Anthony Iliopoulos <ailiop@suse.com> > Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> > --- > v1.1: This time with correct commit message. > --- > m4/package_urcu.m4 | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/m4/package_urcu.m4 b/m4/package_urcu.m4 > index ef116e0cda7..4bb2b886f06 100644 > --- a/m4/package_urcu.m4 > +++ b/m4/package_urcu.m4 > @@ -26,7 +26,11 @@ rcu_init(); > # > # Make sure that calling uatomic_inc on a 64-bit integer doesn't cause a link > # error on _uatomic_link_error, which is how liburcu signals that it doesn't > -# support atomic operations on 64-bit data types. > +# support atomic operations on 64-bit data types for its generic > +# implementation (which relies on compiler builtins). For certain archs > +# where liburcu carries its own implementation (such as x86_32), it > +# signals lack of support during runtime by emitting an illegal > +# instruction, so we also need to check CAA_BITS_PER_LONG to detect that. > # > AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_MSG_CHECKING([for atomic64_t support in liburcu]) > @@ -34,8 +38,11 @@ AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_LANG_PROGRAM([[ > #define _GNU_SOURCE > #include <urcu.h> > +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) > ]], [[ > long long f = 3; > + > +BUILD_BUG_ON(CAA_BITS_PER_LONG < 64); > uatomic_inc(&f); > ]]) > ], have_liburcu_atomic64=yes
On Tue, Sep 12, 2023 at 12:47:51PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > xfsprogs during compilation tries to detect if liburcu supports atomic > 64-bit ops on the platform it is being compiled on, and if not it falls > back to using pthread mutex locks. > > The detection logic for that fallback relies on _uatomic_link_error() > which is a link-time trick used by liburcu that will cause compilation > errors on archs that lack the required support. That only works for the > generic liburcu code though, and it is not implemented for the > x86-specific code. > > In practice this means that when xfsprogs is compiled on 32-bit x86 > archs will successfully link to liburcu for atomic ops, but liburcu does > not support atomic64_t on those archs. It indicates this during runtime > by generating an illegal instruction that aborts execution, and thus > causes various xfsprogs utils to be segfaulting. > > Fix this by requiring that unsigned longs are at least 64 bits in size, > which /usually/ means that 64-bit atomic counters are supported. We > can't simply execute the liburcu atomic64_t detection code during > configure instead of only relying on the linker error because that > doesn't work for cross-compiled packages. > > Fixes: 7448af588a2e ("libxfs: fix atomic64_t poorly for 32-bit architectures") > Reported-by: Anthony Iliopoulos <ailiop@suse.com> > Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Bill O'Donnell <bodonnel@redhat.com> > --- > v1.1: This time with correct commit message. > --- > m4/package_urcu.m4 | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/m4/package_urcu.m4 b/m4/package_urcu.m4 > index ef116e0cda7..4bb2b886f06 100644 > --- a/m4/package_urcu.m4 > +++ b/m4/package_urcu.m4 > @@ -26,7 +26,11 @@ rcu_init(); > # > # Make sure that calling uatomic_inc on a 64-bit integer doesn't cause a link > # error on _uatomic_link_error, which is how liburcu signals that it doesn't > -# support atomic operations on 64-bit data types. > +# support atomic operations on 64-bit data types for its generic > +# implementation (which relies on compiler builtins). For certain archs > +# where liburcu carries its own implementation (such as x86_32), it > +# signals lack of support during runtime by emitting an illegal > +# instruction, so we also need to check CAA_BITS_PER_LONG to detect that. > # > AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_MSG_CHECKING([for atomic64_t support in liburcu]) > @@ -34,8 +38,11 @@ AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_LANG_PROGRAM([[ > #define _GNU_SOURCE > #include <urcu.h> > +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) > ]], [[ > long long f = 3; > + > +BUILD_BUG_ON(CAA_BITS_PER_LONG < 64); > uatomic_inc(&f); > ]]) > ], have_liburcu_atomic64=yes >
On Tue, Sep 12, 2023 at 12:47:51PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > xfsprogs during compilation tries to detect if liburcu supports atomic > 64-bit ops on the platform it is being compiled on, and if not it falls > back to using pthread mutex locks. > > The detection logic for that fallback relies on _uatomic_link_error() > which is a link-time trick used by liburcu that will cause compilation > errors on archs that lack the required support. That only works for the > generic liburcu code though, and it is not implemented for the > x86-specific code. > > In practice this means that when xfsprogs is compiled on 32-bit x86 > archs will successfully link to liburcu for atomic ops, but liburcu does > not support atomic64_t on those archs. It indicates this during runtime > by generating an illegal instruction that aborts execution, and thus > causes various xfsprogs utils to be segfaulting. > > Fix this by requiring that unsigned longs are at least 64 bits in size, > which /usually/ means that 64-bit atomic counters are supported. We > can't simply execute the liburcu atomic64_t detection code during > configure instead of only relying on the linker error because that > doesn't work for cross-compiled packages. > > Fixes: 7448af588a2e ("libxfs: fix atomic64_t poorly for 32-bit architectures") > Reported-by: Anthony Iliopoulos <ailiop@suse.com> > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > --- > v1.1: This time with correct commit message. > --- Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Carlos > m4/package_urcu.m4 | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/m4/package_urcu.m4 b/m4/package_urcu.m4 > index ef116e0cda7..4bb2b886f06 100644 > --- a/m4/package_urcu.m4 > +++ b/m4/package_urcu.m4 > @@ -26,7 +26,11 @@ rcu_init(); > # > # Make sure that calling uatomic_inc on a 64-bit integer doesn't cause a link > # error on _uatomic_link_error, which is how liburcu signals that it doesn't > -# support atomic operations on 64-bit data types. > +# support atomic operations on 64-bit data types for its generic > +# implementation (which relies on compiler builtins). For certain archs > +# where liburcu carries its own implementation (such as x86_32), it > +# signals lack of support during runtime by emitting an illegal > +# instruction, so we also need to check CAA_BITS_PER_LONG to detect that. > # > AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_MSG_CHECKING([for atomic64_t support in liburcu]) > @@ -34,8 +38,11 @@ AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], > [ AC_LANG_PROGRAM([[ > #define _GNU_SOURCE > #include <urcu.h> > +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) > ]], [[ > long long f = 3; > + > +BUILD_BUG_ON(CAA_BITS_PER_LONG < 64); > uatomic_inc(&f); > ]]) > ], have_liburcu_atomic64=yes
diff --git a/m4/package_urcu.m4 b/m4/package_urcu.m4 index ef116e0cda7..4bb2b886f06 100644 --- a/m4/package_urcu.m4 +++ b/m4/package_urcu.m4 @@ -26,7 +26,11 @@ rcu_init(); # # Make sure that calling uatomic_inc on a 64-bit integer doesn't cause a link # error on _uatomic_link_error, which is how liburcu signals that it doesn't -# support atomic operations on 64-bit data types. +# support atomic operations on 64-bit data types for its generic +# implementation (which relies on compiler builtins). For certain archs +# where liburcu carries its own implementation (such as x86_32), it +# signals lack of support during runtime by emitting an illegal +# instruction, so we also need to check CAA_BITS_PER_LONG to detect that. # AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], [ AC_MSG_CHECKING([for atomic64_t support in liburcu]) @@ -34,8 +38,11 @@ AC_DEFUN([AC_HAVE_LIBURCU_ATOMIC64], [ AC_LANG_PROGRAM([[ #define _GNU_SOURCE #include <urcu.h> +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) ]], [[ long long f = 3; + +BUILD_BUG_ON(CAA_BITS_PER_LONG < 64); uatomic_inc(&f); ]]) ], have_liburcu_atomic64=yes