semreset.c

Go to the documentation of this file.

#include <xinu.h>

syscall semreset(sid32 sem, int32 count)
{
    intmask mask;          /* Saved interrupt mask      */
    struct sentry *semptr; /* Ptr to semaphore table entry */
    qid16 semqueue;        /* Semaphore's process queue ID  */
    pid32 pid;             /* ID of a waiting process   */

    mask = disable();

    if (count < 0 || isbadsem(sem) || semtab[sem].sstate == S_FREE)
    {
        restore(mask);
        return SYSERR;
    }

    semptr = &semtab[sem];
    semqueue = semptr->squeue; /* Free any waiting processes */
    resched_cntl(DEFER_START);
    while ((pid = getfirst(semqueue)) != EMPTY)
        ready(pid);
    semptr->scount = count; /* Reset count as specified */
    resched_cntl(DEFER_STOP);
    restore(mask);
    return OK;
}