Glad you found a solution!
3) I'm also convinced now that there is indeed a subtle bug in the gcc pthread
implementation for the mips4 architecture; a scoped_shared_lock as in
handle_data() in sink.cpp can sometimes make the shared_lock try_to_lock in
process() fail, which should not happen.
doesn't that follow from 1)?
So I decided to avoid the try_to_lock shared reader lock in process() for
sink.cpp and source.cpp and converted it to a write_guard (RAII) / generation
counter (keeping all the other write and read locks the same, just for that
reader trylock).
Can you tell me more about that write_guard / generation counter? How
does it work?
Christof
On 8/12/2026 12:41 AM, Wolfgang Gaggl via Pd-list wrote:
Finally, I found a good solution for this trylock issue.
It appears that there are a few things going on platform and compiler dependent:
1) In Irix, trylock does not guarantee a lock on the first try by design even
if uncontested as mentioned in my previous post; trying it a few times can fix
that
2) It appears that trylock can take a bit longer depending on what the system
is doing at the time. Context switching is expensive for this architecture, I
observed that to be even more unpredictable on the Origin than the Octane,
since the NUMA bus and page/cache migration between node boards add layers of
complexity. This can increase the time to obtain a lock.
3) I'm also convinced now that there is indeed a subtle bug in the gcc pthread
implementation for the mips4 architecture; a scoped_shared_lock as in
handle_data() in sink.cpp can sometimes make the shared_lock try_to_lock in
process() fail, which should not happen. And these are very busy, so any lock
failures are eventually converted into xruns.
So I decided to avoid the try_to_lock shared reader lock in process() for
sink.cpp and source.cpp and converted it to a write_guard (RAII) / generation
counter (keeping all the other write and read locks the same, just for that
reader trylock). It works really well since this lock is not contested usually,
no looping needed, no apparent performance expense.
I'm really happy with AOO for PD on SGI Irix now!
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