On 08/19, Roland McGrath wrote:
I think in the longer term mark_engine_detached() should not change
engine-flags at all but add QUIESCE to -utrace_flags. However, this
breaks utrace_maybe_reap(reap = true) and we should avoid the race
with finish_callback() which clears -reporting after
This is the minimal temporary ugly fix for now, we should certainly
cleanup and simplify this logic. The barriers in mark_engine_detached()
and in start_callback() can't help and should be removed. If we ignore
utrace_get_signal() we do not even need utrace_detached_quiesce(),
Suppose that engine-flags == UTRACE_EVENT(EXEC), QUIESCE bit is not set.
1. start_callback() reads want = engine-flags (== EXEC)
2. mark_engine_detached() sets engine-ops = utrace_detached_ops
3. start_callback() gets ops = utrace_detached_ops
After that
