On Sun, May 21, 2017 at 4:59 PM, Gregory Hainaut <gregory.hain...@gmail.com> wrote: > DRI-drivers could call Xlib functions, for example to allocate a new back > buffer. > > When glthread is enabled, the driver runs mostly on a separate thread. > Therefore we need to guarantee the thread safety between libX11 calls > from the applications (not aware of the extra thread) and the ones from > the driver. > > See discussion thread: > https://lists.freedesktop.org/archives/mesa-dev/2017-April/152547.html > > Fortunately, Xlib allows to lock display to ensure thread safety but > XInitThreads must be called first by the application to initialize the lock > function pointer. This patch will allow to check XInitThreads was called > to allow glthread on GLX or EGL platform. > > Note: a tentative was done to port libX11 code to XCB but it didn't solve > fully > thread safety. > See discussion thread: > https://lists.freedesktop.org/archives/mesa-dev/2017-April/153137.html > > Note: Nvidia forces the driver to call XInitThreads. Quoting their manpage: > "The NVIDIA OpenGL driver will automatically attempt to enable Xlib > thread-safe mode if needed. However, it might not be possible in some > situations, such as when the NVIDIA OpenGL driver library is dynamically > loaded after Xlib has been loaded and initialized. If that is the case, > threaded optimizations will stay disabled unless the application is > modified to call XInitThreads() before initializing Xlib or to link > directly against the NVIDIA OpenGL driver library. Alternatively, using > the LD_PRELOAD environment variable to include the NVIDIA OpenGL driver > library should also achieve the desired result." > > v2: based on Nicolai and Matt feedback > Use C style comment > v3: based on Emil feedback > split the patch in 3 > s/isGlThreadSafe/isThreadSafe/ > > Signed-off-by: Gregory Hainaut <gregory.hain...@gmail.com> > --- > include/GL/internal/dri_interface.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/GL/internal/dri_interface.h > b/include/GL/internal/dri_interface.h > index c83056aa70..8381f704e4 100644 > --- a/include/GL/internal/dri_interface.h > +++ b/include/GL/internal/dri_interface.h > @@ -1714,13 +1714,24 @@ struct __DRIbackgroundCallableExtensionRec { > * non-background thread (i.e. a thread that has already been bound to a > * context using __DRIcoreExtensionRec::bindContext()); when this happens, > * the \c loaderPrivate pointer must be equal to the pointer that was > * passed to the driver when the currently bound context was created. > * > * This call should execute quickly enough that the driver can call it > with > * impunity whenever a background thread starts performing drawing > * operations (e.g. it should just set a thread-local variable). > */ > void (*setBackgroundContext)(void *loaderPrivate); > + > + /** > + * Indicate that it is multithread safe to use glthread. For GLX/EGL > + * platforms using Xlib, that involves calling XInitThreads, before > + * opening an X display. > + * > + * \param loaderPrivate is the value that was passed to to the driver when > + * the context was created. This can be used by the loader to identify > + * which context any callbacks are associated with.
There should be a comment that this function is only supported if the extension version is at least 2. Marek > + */ > + GLboolean (*isThreadSafe)(void *loaderPrivate); > }; > > #endif > -- > 2.11.0 > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
