Xorg crashes with SIGABRT in _iris_batch_flush from iris_fence_flush
The most detailed stack trace I've seen is:
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
__GI_abort () at abort.c:79
_iris_batch_flush (batch=batch@entry=0x557db808c938, file=<optimized out>, file@entry=0x7fbec72f6d68 "../src/gallium/drivers/iris/iris_fence.c", line=line@entry=248) at ../src/gallium/drivers/iris/iris_batch.c:750
iris_fence_flush (ctx=0x557db808c4b0, out_fence=0x0, flags=<optimized out>) at ../src/gallium/drivers/iris/iris_fence.c:248
st_flush (flags=0, fence=0x0, st=0x557db80a9900) at ../src/mesa/state_tracker/st_cb_flush.c:60
Downstream Ubuntu bug: https://bugs.launchpad.net/bugs/1871959 but the only instance of the crash with usable debug symbols was https://bugs.launchpad.net/bugs/1915375