[sane-devel] pthread support and MacOS X

[Gerhard Jaeger]

Hi list,

I've done some more changes to the sanei_thread library:
- supports either fork or pthread stuff
This means:
 sanei_thread_begin -->  uses fork and starts the function in child context
                         or uses pthread_create
 sanei_thread_kill and
 sanei_thread_waitpid --> are mapped to kill/waitpid or pthread_kill/
                          pthread_join

The goal is to allow the usage of sanei_thread in any case. Two additional
functions are
 sanei_thread_init --> mainly to initialize the debug interface
 sanei_thread_is_forked --> to distinguish in the backend if we're forked
                            or not, as some diffs in the backend might remain
                            between the two models

I've also updated the tests in the configure script. You'll find the switch
--enable-fork-process, with is used to override the default settings for
pthread/fork usage. The default is: use pthread on Darwin (if available), else
use fork.

The migration to this sanei_thread stuff is not complete now, but if nobody
has objections on that, I'd like to adapt the test-backend, to show the usage.

Any comments?

Ciao,
  Gerhard


On Sonntag, 5. Oktober 2003 23:54, Henning Meier-Geinitz wrote:
> Hi,
>
> On Sun, Oct 05, 2003 at 06:16:12PM +0200, Jaeger, Gerhard wrote:
> > I've currently added pthread support to the sanei_thread lib and changed
> > the Plustek backend, so that it will use threading instead of forking on
> > MacOS X. Could somebody please test this?
> > Also the detection of pthreads is not correct, please test also...
>
> Just some quick comments, I'll test more during the next few days:
>
> - I think it's good to have support for different types of fork/thread
>   whatever. However, I'd like to have that completely in sanei_thread
>   (or wherever). So I'd call sanei_thread_begin in my backend and
>   don't care if it expands to pthreads, OS/2 threads or fork. This
>   means some limitations (e.g. only one parameter for OS/2?) and we
>   have to check that the reader processes work with both threads and
>   processes. Otherwise we must have #ifdefs for 3 platforms in our
>   backends as both OS/2 and MacOS need special care now. MacOSX needs
>   sanei_thread_whatever, OS/2 needs fork() and a encapsulated
>   reader_process and everything else needs fork() only.
>
> - The docu in include/sane/sanei_thread.h should be updated (but only
>   when we are sure if we keep the current implementation)
>
> - SANE_CHECK_PTHREAD must go into acinclude.m4. aclocal.m4 is
>   generated automatically from acinclude.m4 when you run "aclocal".
>   (After that run autoheader and autoconf). Otherwise it would be
>   deleted by the next run of aclocal.
>
> - Linking fails on Free- and OpenBSD. I had only a quick look
>   but I think it's because they don't have a libpthread but pthread.h.
>   Before adding -lpthread you should check if the lib is available
>   (not only a header). Maybe you should check for the header first and
>   then if one of the pthread functions is available (in libc). If it
>   isn't, try if it's available in libpthread and link that lib.
>
> - I'm not sure if we should use threads by default (link to
>   libpthread) or only on MacOS X. Maybe that should be a configure
>   option (--enable-pthreads: default yes on MAcOS, no everwhere else)?
>
> There are other compilation/linking problems on other platforms but
> they may not be related to pthread. I'll look later.
>
> Bye,
>   Henning