On Fri, Jan 05, 2018 at 11:25:17AM -0500, Jeff Moyer wrote:
> Christoph Hellwig <hch@xxxxxx> writes:
>
> > This way it can be used for the fallback 6-argument version on
> > all architectures.
> >
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
>
> This is a strange way to do things. However, I was never really sold on
> libaio having to implement its own system call wrappers. That decision
> definitely resulted in some maintenance overhead.
>
> Ben, what was your reasoning for not just using syscall?
The main issue was that glibc's pthreads implementation really sucked back
during initial development and there was a use-case for having the io_XXX
functions usable directly from clone()ed threads that didn't have all the
glibc pthread state setup for per-cpu areas to handle per-thread errno.
That made sense back then, but is rather silly today.
Technically, I'm not sure the generic syscall wrapper is safe to use. The
io_XXX arch wrappers don't modify errno, while it appears the generic one
does. That said, nobody has ever noticed...
-ben
> -Jeff
>
> > ---
> > src/syscall-generic.h | 6 ------
> > src/syscall.h | 7 +++++++
> > 2 files changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/src/syscall-generic.h b/src/syscall-generic.h
> > index 24d7c7c..35b8580 100644
> > --- a/src/syscall-generic.h
> > +++ b/src/syscall-generic.h
> > @@ -2,12 +2,6 @@
> > #include <unistd.h>
> > #include <sys/syscall.h>
> >
> > -#define _body_io_syscall(sname, args...) \
> > -{ \
> > - int ret = syscall(__NR_##sname, ## args); \
> > - return ret < 0 ? -errno : ret; \
> > -}
> > -
> > #define io_syscall1(type,fname,sname,type1,arg1) \
> > type fname(type1 arg1) \
> > _body_io_syscall(sname, (long)arg1)
> > diff --git a/src/syscall.h b/src/syscall.h
> > index a2da030..3819519 100644
> > --- a/src/syscall.h
> > +++ b/src/syscall.h
> > @@ -10,6 +10,13 @@
> > #define DEFSYMVER(compat_sym, orig_sym, ver_sym) \
> > __asm__(".symver " SYMSTR(compat_sym) "," SYMSTR(orig_sym) "@@LIBAIO_" SYMSTR(ver_sym));
> >
> > +/* generic fallback */
> > +#define _body_io_syscall(sname, args...) \
> > +{ \
> > + int ret = syscall(__NR_##sname, ## args); \
> > + return ret < 0 ? -errno : ret; \
> > +}
> > +
> > #if defined(__i386__)
> > #include "syscall-i386.h"
> > #elif defined(__x86_64__)
>
--
"Thought is the essence of where you are now."
