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31 lines
746 B
31 lines
746 B
/* signal.c - signal */ |
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#include <xinu.h> |
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/*------------------------------------------------------------------------ |
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* signal - Signal a semaphore, releasing a process if one is waiting |
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*------------------------------------------------------------------------ |
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*/ |
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syscall signal( |
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sid32 sem /* ID of semaphore to signal */ |
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) |
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{ |
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intmask mask; /* Saved interrupt mask */ |
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struct sentry *semptr; /* Ptr to sempahore table entry */ |
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mask = disable(); |
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if (isbadsem(sem)) { |
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restore(mask); |
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return SYSERR; |
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} |
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semptr= &semtab[sem]; |
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if (semptr->sstate == S_FREE) { |
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restore(mask); |
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return SYSERR; |
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} |
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if ((semptr->scount++) < 0) { /* Release a waiting process */ |
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ready(dequeue(semptr->squeue)); |
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} |
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restore(mask); |
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return OK; |
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}
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