[PD] pthread_setschedparam problem on OSX + fix

cgc cgc at humboldtblvd.com
Sun Nov 23 22:18:21 CET 2003

I've been meaning to post this change for a long time, and have been 
negligent about it.

The pthread_setschedparam() hack that helps pd's audio not drop on OSX 
is absolutely fatal when used with GEM.  The reason for this is that 
OSX uses OpenGL for the entire UI and GL requires context switches to 
handle multiple applications sharing the hardware.  When Pd sets it's 
pthread priority higher than the UI, this context switch can be blocked 
resulting in a complete lockout of UI events as GEM grabs all the CPU 
resources and refuses to relinquish the context.

The fix is to add the -rt option as prerequisite and not make this the 
default action (a check to make sure GEM is not loaded would be good to 
have as well):

#ifdef MACOSX

     if (sys_hipriority)
	struct sched_param param;
	int policy = SCHED_RR;
	int err;
	param.sched_priority = 80; // adjust 0 : 100
         post("pd: real-time mode - using pthread_setschedparam\n");
	err = pthread_setschedparam(pthread_self(), policy, &param);
	if (err)
	    post("warning: high priority scheduling failed\n");
#endif /* MACOSX */

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