Reported to nvidia-vaapi-driver bug tracker:
https://github.com/elFarto/nvidia-vaapi-driver/issues/164

#0  futex_wait (private=0, expected=2, futex_word=0x7fd570a20228) at ../sysdeps/nptl/futex-internal.h:146
#1  __GI___lll_lock_wait (futex=futex@entry=0x7fd570a20228, private=0) at lowlevellock.c:49
#2  0x00007fd570c91412 in lll_mutex_lock_optimized (mutex=0x7fd570a20228) at pthread_mutex_lock.c:48
#3  ___pthread_mutex_lock (mutex=0x7fd570a20228) at pthread_mutex_lock.c:93
#4  0x00007fd56db28311 in egl_allocateBackingImage () at /usr/lib64/dri/nvidia_drv_video.so
#5  0x00007fd56db2ce8a in egl_realiseSurface () at /usr/lib64/dri/nvidia_drv_video.so
#6  0x00007fd56db2a29d in nvExportSurfaceHandle () at /usr/lib64/dri/nvidia_drv_video.so
#7  0x00007fd562212535 in vaExportSurfaceHandle (dpy=0x7fd570a3e760, surface_id=24, mem_type=1073741824, flags=5, descriptor=0x7fd55e500170) at ../va/va.c:1561
#8  0x00007fd567aa41f0 in mozilla::FFmpegVideoDecoder<46465650>::GetVAAPISurfaceDescriptor(_VADRMPRIMESurfaceDescriptor*)