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Annotation of lucent/sys/src/9/gnot/scsibuf.c, revision 1.1

1.1     ! root        1: #include "u.h"
        !             2: #include "../port/lib.h"
        !             3: #include "mem.h"
        !             4: #include "dat.h"
        !             5: #include "fns.h"
        !             6: #include "../port/error.h"
        !             7: #include "io.h"
        !             8: 
        !             9: /*
        !            10:  * The following routines
        !            11:  *     scsibufreset, scsibuf, scsifree and scsialloc
        !            12:  * provide a pool of buffers used for scsi i/o.
        !            13:  * This is simplistic at best, and opportunities for
        !            14:  * deadlock abound.
        !            15:  */
        !            16: #define Nbuf   1
        !            17: 
        !            18: struct {
        !            19:        Lock;
        !            20:        Scsibuf *free;
        !            21: } scsibufalloc;
        !            22: 
        !            23: void
        !            24: scsibufreset(ulong datasize)
        !            25: {
        !            26:        int i;
        !            27: 
        !            28:        for(i = 0; i < Nbuf; i++)
        !            29:                scsifree(scsialloc(datasize));
        !            30:        lock(&scsibufalloc);
        !            31:        unlock(&scsibufalloc);
        !            32: }
        !            33: 
        !            34: /*
        !            35:  * get a scsi io buffer of DATASIZE size
        !            36:  */
        !            37: Scsibuf *
        !            38: scsibuf(void)
        !            39: {
        !            40:        Scsibuf *b;
        !            41: 
        !            42:        for(;;) {
        !            43:                lock(&scsibufalloc);
        !            44:                b = scsibufalloc.free;
        !            45:                if(b != 0) {
        !            46:                        scsibufalloc.free = b->next;
        !            47:                        unlock(&scsibufalloc);
        !            48:                        return b;
        !            49:                }
        !            50:                unlock(&scsibufalloc);
        !            51:                resrcwait(0);
        !            52:        }
        !            53:        return 0;               /* not reached */
        !            54: }
        !            55: 
        !            56: void
        !            57: scsifree(Scsibuf *b)
        !            58: {
        !            59:        lock(&scsibufalloc);
        !            60:        b->next = scsibufalloc.free;
        !            61:        scsibufalloc.free = b;
        !            62:        unlock(&scsibufalloc);
        !            63: }

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