usleep and sound, signals and threads

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3 total messages Started by Sam Streeper Tue, 03 Nov 1992 22:20

#125

Author: Sam Streeper
Date: Tue, 03 Nov 1992 22:20

29 lines
1342 bytes

Someone was just trying to add sound to a BackSpace module and ran into a  
sneaky problem that has been discussed before but bears repeating.

usleep() is implemented via signals (a questionable strategy IMHO), and many of  
the soundkit functions surreptitiously use threads to keep the sound buffers  
full.  Signals and threads do not mix gracefully, and the sound thread may  
catch the signal that was supposed to wake up the usleep() function, hanging it  
forever.

The solution is to pick some waiting method that doesn't use signals; for  
example waiting on a mach port.

One easy way to do this is to wait for an event that will never be received  
with an appropriate timeout.  For example:

	NXEvent dummyEvent;

	[NXApp peekNextEvent:0 
		into:&dummyEvent 
		waitFor:timeout
		threshold: NX_MODALRESPTHRESHOLD];

Maybe this will keep someone from tearing one's hair out.

-sam

--
Opinions expressed herein are not those of my employer.  They're not even
mine.  There is water at the bottom of the ocean.  Hi Mom!

Re: usleep and sound, signals and threads

#134

Author: felix.lugo
Date: Wed, 04 Nov 1992 01:17

26 lines
1096 bytes

In article <5724@rosie.NeXT.COM> sam_s@NeXT.com writes:
| 
| The solution is to pick some waiting method that doesn't use signals; for  
| example waiting on a mach port.
| 
| One easy way to do this is to wait for an event that will never be received  
| with an appropriate timeout.  For example:
| 
| 	NXEvent dummyEvent;
| 
| 	[NXApp peekNextEvent:0 
| 		into:&dummyEvent 
| 		waitFor:timeout
| 		threshold: NX_MODALRESPTHRESHOLD];
| 
| Maybe this will keep someone from tearing one's hair out.
| 
| -sam
| 
| --
| Opinions expressed herein are not those of my employer.  They're not even
| mine.  There is water at the bottom of the ocean.  Hi Mom!

	What's wrong with using good'ol select()?

--Felix

Re: usleep and sound, signals and threads

#137

Author: Chris Lloyd
Date: Wed, 04 Nov 1992 06:07

17 lines
998 bytes

In article <1992Nov4.011720.12191@cbnewsl.cb.att.com> coco@cbnewsl.cb.att.com (felix.lugo) writes:
>In article <5724@rosie.NeXT.COM> sam_s@NeXT.com writes:
>| 	NXEvent dummyEvent;
>| 
>| 	[NXApp peekNextEvent:0 
>| 		into:&dummyEvent 
>| 		waitFor:timeout
>| 		threshold: NX_MODALRESPTHRESHOLD];
>
>	What's wrong with using good'ol select()?


       thread_switch(THREAD_NULL,SWITCH_OPTION_WAIT,milliseconds);

la la la,
-- 
::   Christopher Lloyd  ::  a74k110@titan.ucc.umass.edu  ::  Yrrid, Inc.    ::

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