Re: Is there spinlocks/semaphores available for drivers?

[Matthew Dillon]

SMP FIFO (one writer, one reader):

        #define SIZE    256
        #define MASK    (SIZE-1)

        int ri;
        int wi;
        int fifo[SIZE];

        int
        fifo_read(void)
        {
            int r = -1;

            if (ri != wi) {
                int nri;

                r = fifo[ri];
                nri = (ri + 1) & MASK;
                ri = nri;
            }
            return(r);
        }

        int
        fifo_write(int v)
        {
            int nwi = (wi + 1) & MASK;

            if (nwi != ri) {
                fifo[wi] = v;
                wi = nwi;
                return(0);
            } else {
                return(-1);
            }
        }

        int
        fifo_ready()
        {
            return((wi - ri) & MASK)
        }

        int
        fifo_space()
        {
            return(SIZE - nready() - 1);
        }




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