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Annotation of coherent/b/kernel/coh.386/poll.c, revision 1.1

1.1     ! root        1: /* $Header: /y/coh.386/RCS/poll.c,v 1.3 93/04/14 10:06:42 root Exp $ */
        !             2: /*
        !             3:  *     The  information  contained herein  is a trade secret  of INETCO
        !             4:  *     Systems, and is confidential information.   It is provided under
        !             5:  *     a license agreement,  and may be copied or disclosed  only under
        !             6:  *     the terms of that agreement.   Any reproduction or disclosure of
        !             7:  *     this  material  without  the express  written  authorization  of
        !             8:  *     INETCO Systems or persuant to the license agreement is unlawful.
        !             9:  *
        !            10:  *     Copyright (c) 1986
        !            11:  *     An unpublished work by INETCO Systems, Ltd.
        !            12:  *     All rights reserved.
        !            13:  */
        !            14: 
        !            15: /*
        !            16:  * [Stream] Polling.
        !            17:  *
        !            18:  *     void pollinit() -- allocate polling buffers
        !            19:  *     int pollopen(qp) -- enable polling  by current process  on given queue
        !            20:  *     int pollwake(qp) -- wake all processes waiting for poll on given queue
        !            21:  *     int pollexit() -- terminate all polls enabled by current process
        !            22:  *     event_t * ep;
        !            23:  *
        !            24:  * $Log:       poll.c,v $
        !            25:  * Revision 1.3  93/04/14  10:06:42  root
        !            26:  * r75
        !            27:  * 
        !            28:  * Revision 1.2  92/01/06  11:59:56  hal
        !            29:  * Compile with cc.mwc.
        !            30:  * 
        !            31:  * Revision 1.1        88/03/24  16:14:10      src
        !            32:  * Initial revision
        !            33:  * 
        !            34:  * 86/11/19    Allan Cornish           /usr/src/sys/coh/poll.c
        !            35:  * Ported to Coherent from RTX.
        !            36:  */
        !            37: 
        !            38: #include <sys/coherent.h>
        !            39: #include <sys/proc.h>
        !            40: 
        !            41: /*
        !            42:  * Patchable data.
        !            43:  */
        !            44: int    NPOLL  = 0;
        !            45: 
        !            46: /*
        !            47:  * Private data.
        !            48:  */
        !            49: static event_t * efreep;
        !            50: 
        !            51: /**
        !            52:  *
        !            53:  * event_t *
        !            54:  * pollinit()          -- allocate event buffers.
        !            55:  */
        !            56: event_t *
        !            57: pollinit()
        !            58: {
        !            59:        register event_t * ep;
        !            60:        register event_t * ap;
        !            61:        static int first = 1;
        !            62: 
        !            63:        /*
        !            64:         * If dynamically growing event pool is specified [NPOLL == 0],
        !            65:         * try to allocate an additional cluster of 32 on each call.
        !            66:         */
        !            67:        if (NPOLL == 0) {
        !            68:                if (ep = kalloc(32 * sizeof(event_t)))
        !            69:                        ap = ep + 32;
        !            70:        }
        !            71: 
        !            72:        /*
        !            73:         * If statically sized event pool is specified [NPOLL != 0],
        !            74:         * try to allocate the pool on the first call.
        !            75:         */
        !            76:        else if (first) {
        !            77:                first = 0;
        !            78:                if (ep = kalloc(NPOLL * sizeof(event_t)))
        !            79:                        ap = ep + NPOLL;
        !            80:        }
        !            81: 
        !            82:        /*
        !            83:         * If event cluster was allocated, insert into free event queue.
        !            84:         */
        !            85:        if (ep) {
        !            86:                do {
        !            87:                        ep->e_pnext = efreep;
        !            88:                        efreep = ep;
        !            89:                } while (++ep < ap);
        !            90:        }
        !            91: 
        !            92:        return efreep;
        !            93: }
        !            94: 
        !            95: /**
        !            96:  *
        !            97:  * int
        !            98:  * pollopen(qp) -- enable polling by current process on given event queue
        !            99:  * event_t * qp;
        !           100:  */
        !           101: pollopen(qp)
        !           102: register event_t * qp;
        !           103: {
        !           104:        register event_t * ep;
        !           105: 
        !           106:        /*
        !           107:         * Initialize device queue if required.
        !           108:         */
        !           109:        if (qp->e_dnext == 0)
        !           110:                qp->e_dnext = qp->e_dlast = qp;
        !           111: 
        !           112:        /*
        !           113:         * Obtain a free event buffer, or return.
        !           114:         */
        !           115:        if (((ep = efreep) == 0) && ((ep = pollinit()) == 0)) {
        !           116:                printf("out of poll buffers\n");
        !           117:                return;
        !           118:        }
        !           119: 
        !           120:        /*
        !           121:         * Remove event buffer from free queue.
        !           122:         */
        !           123:        efreep = ep->e_pnext;
        !           124: 
        !           125:        /*
        !           126:         * Record process pointer in event buffer.
        !           127:         */
        !           128:        ep->e_procp = cprocp;
        !           129: 
        !           130:        /*
        !           131:         * Insert event at head of process event singularly-linked queue.
        !           132:         */
        !           133:        ep->e_pnext = cprocp->p_polls;
        !           134:        cprocp->p_polls = ep;
        !           135: 
        !           136:        /*
        !           137:         * Insert event at tail of circularly-linked device queue.
        !           138:         * This ensures that processes are first-in first-out.
        !           139:         */
        !           140:        ep->e_dnext  = qp;
        !           141:        (ep->e_dlast = qp->e_dlast)->e_dnext = ep;
        !           142:        qp->e_dlast  = ep;
        !           143: 
        !           144:        /*
        !           145:         * Record last process to enable polling on device.
        !           146:         */
        !           147:        qp->e_procp = cprocp;
        !           148: }
        !           149: 
        !           150: /**
        !           151:  *
        !           152:  * int
        !           153:  * pollwake(qp) -- wake all processes waiting for poll on given queue
        !           154:  * event_t * qp;
        !           155:  *
        !           156:  * Go through extra step of deferring the pollwake to avoid race condition
        !           157:  * (in case interrupt handler does a pollwake() during upoll()).
        !           158:  */
        !           159: pollwake(qp)
        !           160: event_t * qp;
        !           161: {
        !           162:        void dpollwake();
        !           163: 
        !           164:        defer(dpollwake, qp);
        !           165: }
        !           166: 
        !           167: void
        !           168: dpollwake(qp)
        !           169: event_t * qp;
        !           170: {
        !           171:        register event_t * ep = qp;
        !           172:        register PROC    * pp;
        !           173: 
        !           174:        /*
        !           175:         * Clear device process pointer, indicating poll completed.
        !           176:         * NOTE: interrupt handlers may have already cleared it.
        !           177:         */
        !           178:        qp->e_procp = 0;
        !           179: 
        !           180:        if (ep = qp->e_dnext) {
        !           181: 
        !           182:                /*
        !           183:                 * Service circularly-linked polls on device queue.
        !           184:                 */
        !           185:                while (ep != qp) {
        !           186:                        /*
        !           187:                         * Wake process if it is sleeping.
        !           188:                         */
        !           189:                        if ((pp = ep->e_procp) && ASLEEP(pp))
        !           190:                                wakeup(&pp->p_polls);
        !           191: 
        !           192:                        ep = ep->e_dnext;
        !           193:                }
        !           194:        }
        !           195: }
        !           196: 
        !           197: /**
        !           198:  *
        !           199:  * int
        !           200:  * pollexit() -- terminate all polls opened by current process
        !           201:  */
        !           202: int
        !           203: pollexit()
        !           204: {
        !           205:        register PROC    * pp = cprocp;
        !           206:        register event_t * ep;
        !           207: 
        !           208:        /*
        !           209:         * Service all polling event buffers enabled by current process.
        !           210:         */
        !           211:        while (ep = pp->p_polls) {
        !           212: 
        !           213:                /*
        !           214:                 * Remove event buffer from circularly-linked device queue.
        !           215:                 */
        !           216:                (ep->e_dnext->e_dlast = ep->e_dlast)->e_dnext = ep->e_dnext;
        !           217: 
        !           218:                /*
        !           219:                 * Remove event buffer from singularly-linked process queue.
        !           220:                 */
        !           221:                pp->p_polls = ep->e_pnext;
        !           222: 
        !           223:                /*
        !           224:                 * Insert event buffer at head of free event buffer queue.
        !           225:                 */
        !           226:                ep->e_pnext = efreep;
        !           227:                efreep = ep;
        !           228:        }
        !           229: }

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