Hi Sebastian,
On Jul 8, 2010, at 9:46 AM, Sebastian Good wrote:
> Does read-only HDF usage tolerate multi-threading? I was under the impression
> that enabling threading simply added a mutex around critical operations. Is
> there a difference between platforms, e.g. Linux & Windows?
You must still enable thread-safety for the HDF5 library even when
performing read-only access to files. There are plenty of internal [memory]
data structures that will likely blow up currently without the global mutex to
only let one thread in at a time.
Currently, we don't support multi-threaded access on Windows, although
we are making some progress in that area currently.
Quincey
> Cheers,
>
> Sebastian
>
> On Thu, Jul 8, 2010 at 6:00 AM, Quincey Koziol <[email protected]> wrote:
> Hi Richard,
>
> On Jul 7, 2010, at 3:47 AM, Richard Khoury wrote:
>
> > Hello,
> > After writing an application that allows the user to flip between loading
> > and saving a H5 file, a few objects within the file weren't closing
> > properly which didn't allow the file to close when I called H5Fclose. Going
> > from a loading state (H5open) to a saving state (H5create or H5open with
> > RDWR access) complained that the file was still open so I implemented a
> > simple routine to close all open objects within a file before calling
> > H5Fclose:
> >
> > void close_all_objects_within_file (hid_t file_id)
> > {
> > ssize_t numOpenObjs = H5Fget_obj_count(file_id, H5F_OBJ_ALL);
> > hid_t *obj_id_list = (hid_t*)(malloc(numOpenObjs * sizeof(hid_t)));
> > ssize_t numReturnedOpenObjs = H5Fget_obj_ids(file_id, H5F_OBJ_ALL,
> > numOpenObjs, obj_id_list);
> > for (ssize_t i = 0; i < numReturnedOpenObjs; ++i)
> > {
> > H5Oclose(obj_id_list[i]);
> > }
> > free(obj_id_list);
> > }
> >
> > This worked fine until the application became multi-threaded, and a call to
> > close_all_objects_within_file(file_id) was crashing the program. It seems
> > that the object resources are shared between the threads that have opened
> > the same file, and the first thread to call this routine kills any chance
> > of another thread to use that resource. Is this correct?
>
> Yes.
>
> > If this is case, is there a way I can check (in the for-loop above) if the
> > object is being referenced by another thread before doing an H5Oclose? Or
> > perhaps there's a better way to close all the resources of a file? Or maybe
> > I'm going about this the wrong way, in which case I'm very much open to
> > suggestions.
>
> You probably want to use the H5Pset_fclose_degree() routine.
>
> Quincey
>
>
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