Re: [Boost-users] [Threads] Conditions and avoiding lengthy mutex locks (background loading for a game)

You usually don't hold the mutex guarding the state indicating variables for a long time. You usually hold it just enough to update the variables to indicate the new state you have transitioned to. That is you hold it while you pick up the request from the queue and transfer it to local variables in the thread (or somehow mark it in the queue) as being processed, then you release the lock and go off and handle request. After you are done processing you grab the lock again and update state or lock for new requests and then repeat. If there are no requests then you block on condition while holding the mutex and the blocking wait releases and reacquires the lock for you when the condition is signaled. You will be holding the mutex lock for very little time unless popping/marking queue elements is quite expensive. Also, it often a little more efficient to signal the condition variable while not holding the mutex. It can avoid needless context ping ponging. On Apr 27, 2006, at 3:49 PM, Peter Mackay wrote:

Hello,

I'm trying to use the Boost Threads library to help me implement a background loading system for a game I'm writing.

I want to enqueue load requests while the main game thread is running, and have a separate thread load the data and pass back the appropriate objects.

Currently when I enqueue a new request, I notify a 'something to do' condition, which my loading thread waits on. The trouble is, when I notify it, the loader could be loading in the background, and has a lock on the mutex connected with the condition. Would anyone be able to offer me any advice on how to solve this?

Many thanks, Peter

P.S. Please find attached my current implementation.

begin 666 loader.cpp M(VEN8VQU9&4@(FQO861EPT*"2\O(%-I9VYA;"!T:&4@=&AR M96%D('1O(&5X:70N#0H)>PT*"0EB;V]S=#HZ;75T97@Z.G-C;W!E9%]L;V-K M(&QO8VLH;75T97@I.PT*"0ET:')E861?PT*"0DO+R!786ET('5N=&EL('=E(&=E="!S;VUE=&AI;F<@ M=&\@9&\N#0H)"7-O;65T:&EN9U]T;U]D;RYW86ET*&QO8VLI.PT*#0H)"2\O M(%-H;W5L9"!W92!E>&ET/PT*"0EI9B H=&AR96%D7W-H;W5L9%]E>&ET*0T* M"0E[#0H)"0DO+R!%>&ET('1H92!T:')E860N#0H)"0ER971U

begin 666 loader.hpp M(VEF;F1E9B!,3T%$15)?2%!0#0HC9&5F:6YE($Q/041%4E](4% -"@T*(VEN M8VQU9&4@/'%U975E/@T*(VEN8VQU9&4@/&)O;W-T+W-H87)E9%]P='(N:'!P M/@T*(VEN8VQU9&4@/&)O;W-T+W1H"YH<' ^#0HC:6YC;'5D92 \8F]O M&ET M.PT*"7-T9#HZ<75E=64\:6YT/@D)<&5N9&EN9U]L;V%D2X-"@EB;V]S=#HZ

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