pthread_barrier_t is not working properly

[X512]

This is hrev53888.

pthread_barrier_t is causing freeze on start of OpenGL applications on multicore systems.

Disabling pthread_barrier_t in Mesa and using Mesa own implementation fixes freeze.

[X512]

Mesa patch to disable pthread_barrier_t

[korli]

​https://github.com/mesa3d/mesa/blob/master/src/util/u_thread.h#L182

[waddlesplash]

Do you have a simple testcase that shows the problem? That would be helpful here.

[X512]

I don't identified exact problem yet. To reproduce problem, apply ​this patch to mesa, enable pthread_barrier_t and run GLTeapot. It will freeze. Freeze appear in render threads.

[waddlesplash]

A first step would be attaching a debugger and determining what is waiting and where/why inside libroot's pthread_barrier.cpp.

Actually, looking at that code briefly, I'm not sure why it uses the kernel mutex API directly, rather than using the user_mutex wrappers, seems a little strange. I guess because it needs to do B_USER_MUTEX_UNBLOCK_ALL?

[X512]

Mesa has its own implementation of barrier that can be used as reference: ​https://github.com/mesa3d/mesa/blob/master/src/util/u_thread.h#L204.

[waddlesplash]

Well, there is ​https://xref.landonf.org/source/xref/haiku/src/tests/system/libroot/posix/pthread_barrier_test.cpp which seems to test the relevant functionality, so I'm not sure what else Mesa could be doing that is causing problems.

[cocobean]

pthread_barrier_t considered optional POSIX feature - not widely used/portable for UNIX 98/2003-compatibility.

[waddlesplash]

Fixed in hrev57071.