<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - Concurrent call to glClientWaitSync results in segfault in one of the waiters." href="https://bugs.freedesktop.org/show_bug.cgi?id=98172#c8">Comment # 8</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - Concurrent call to glClientWaitSync results in segfault in one of the waiters." href="https://bugs.freedesktop.org/show_bug.cgi?id=98172">bug 98172</a> from <a class="email" href="mailto:shinji.suzuki@gmail.com" title="shinji.suzuki@gmail.com">shinji.suzuki@gmail.com</a> <pre>Comment on <a href="attachment.cgi?id=127267" name="attach_127267" title="Lock the shared state mutex and work with a local reference of so->fence">attachment 127267</a> <a href="attachment.cgi?id=127267&action=edit" title="Lock the shared state mutex and work with a local reference of so->fence">[details]</a> <a href='page.cgi?id=splinter.html&bug=98172&attachment=127267'>[review]</a> Lock the shared state mutex and work with a local reference of so->fence Review of <a href="attachment.cgi?id=127267" name="attach_127267" title="Lock the shared state mutex and work with a local reference of so->fence">attachment 127267</a> <a href="attachment.cgi?id=127267&action=edit" title="Lock the shared state mutex and work with a local reference of so->fence">[details]</a> <a href='page.cgi?id=splinter.html&bug=98172&attachment=127267'>[review]</a>: ----------------------------------------------------------------- I'm afraid execution of st_fence_sync() can still race. Thread-A can run upto success = screen->fence_finish(screen, pipe, fence, 0); and then get prempted and Thread-B can run upto the same location. And then screen->fence_reference(screen, &so->fence, NULL); can still be executed in arbitrary order. If screen->fence_refrence() is thread-safe and return true only for the first invocation then all is fine but likely it is not true as otherwise we will not be struggling with this issue. I think the gist of it is that checking of so->fence and nullifying of it should be executed atomically. If "if (success)" is replaced with "if (success && so->fence)" then the program may behave correctly but I'm not confortable about sreen->fence_ference() being called concurrently. I'm also concerned that mutual exclusion on ctx->Shared->Mutex may introduce unnecessarily strict serialization. Can't we introduce per sync-object mutex so that excution of checking of so->fence and nullyfying of it happen atomically? Is that modification too intrusive? (At least it is unnecessary overhead when st_fence_sync() is not executed concurrently on the same sync object.)</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>