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Annotation of driverkit/notes/diskIoThreadCondition, revision 1.1.1.1

1.1       root        1: disk I/O thread - qlock conditions
                      2: 
                      3: work to do (ALL threads should wake up and run main loop once) when
                      4:        anything is added to either q (q_disk, q_nodisk), or
                      5:        -diskPresent needs to wakeup I/O thread to tell it "disk present"
                      6:                
                      7: another way:
                      8: work to do when 
                      9:        q_nodisk non-empty, or
                     10:        ((!queue_empty(q_disk)) &&
                     11:                (lastReadyState != RS_NODISK) &&
                     12:                (lastReadyState != RS_EJECTING) &&
                     13:                (!ejectPending)) 
                     14:                
                     15: threads sleep when
                     16:        q_disk and q_nodisk empty
                     17:        q_nodisk empty && no disk present
                     18:        
                     19: Update condition variable (WORK_TO_DO/NO_WORK_TO_DO):
                     20:        -- enqueueIoBuf - set uncond to WORK_TO_DO
                     21:        -- ioThreadWakeup - set uncond to WORK_TO_DO
                     22:        -- in I/O thread - before sleeping (to end of loop, at final unlock).
                     23:        
                     24: @interface NXCondition
                     25: {
                     26: 
                     27: }
                     28: 
                     29: - signal;
                     30: - broadcast;
                     31: - wait;
                     32: 
                     33: ...IOThread:
                     34: {
                     35:        while(1) {
                     36:                service q_nodisk;
                     37:                service q_disk if appropriate;
                     38:                cal volCheckRequest if appropriate;
                     39:                [NXcondition wait];
                     40:        }
                     41: }
                     42: 
                     43: enqueueIoBuf:
                     44: {
                     45:        [qlock lock];
                     46:        enqueue IOBuf;
                     47:        [NXCondition broadcast];                // need a lock for this too?
                     48:        [qlock unlock];
                     49: }
                     50: ..............
                     51: 
                     52: How about NXConditionLock..
                     53: in IOQueue:
                     54:        int workToDo;   
                     55:        
                     56: This is the "thread-work quanta" to do. Each IOBuf enqueued 
                     57: 
                     58: enqueueIoBuf
                     59: {
                     60:        [qlock lock];
                     61:        enqueue IOBuf;
                     62:        workToDo += numThreads;
                     63:        [qlock unlockWith:WORK_TO_DO];
                     64: }
                     65: 
                     66: IOThread
                     67: {
                     68:        while(1) {
                     69:                [qlock lockWhen:WORK_TO_DO];
                     70:                workToDo--;
                     71:                if(workToDo == 0)
                     72:                        [qlock unlockWith:NO_WORK_TO_DO];
                     73:                else
                     74:                        [qlock unlock];
                     75:                service queues;
                     76:                // all other unlocks leave condition variable alone.
                     77:        }
                     78: }

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