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      1 /*	$NetBSD: klock.c,v 1.11 2023/06/23 21:09:44 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2007-2010 Antti Kantee.  All Rights Reserved.
      5  *
      6  * Development of this software was supported by the
      7  * Finnish Cultural Foundation.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
     19  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     21  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 __KERNEL_RCSID(0, "$NetBSD: klock.c,v 1.11 2023/06/23 21:09:44 riastradh Exp $");
     33 
     34 #include <sys/param.h>
     35 #include <sys/systm.h>
     36 #include <sys/evcnt.h>
     37 
     38 #include <rump-sys/kern.h>
     39 
     40 #include <rump/rumpuser.h>
     41 
     42 /*
     43  * giant lock
     44  */
     45 
     46 struct rumpuser_mtx *rump_giantlock;
     47 static int giantcnt;
     48 static struct lwp *giantowner;
     49 
     50 static struct evcnt ev_biglock_fast;
     51 static struct evcnt ev_biglock_slow;
     52 static struct evcnt ev_biglock_recurse;
     53 
     54 void
     55 rump_biglock_init(void)
     56 {
     57 
     58 	evcnt_attach_dynamic(&ev_biglock_fast, EVCNT_TYPE_MISC, NULL,
     59 	    "rump biglock", "fast");
     60 	evcnt_attach_dynamic(&ev_biglock_slow, EVCNT_TYPE_MISC, NULL,
     61 	    "rump biglock", "slow");
     62 	evcnt_attach_dynamic(&ev_biglock_recurse, EVCNT_TYPE_MISC, NULL,
     63 	    "rump biglock", "recurse");
     64 }
     65 
     66 void
     67 rump_kernel_bigwrap(int *nlocks)
     68 {
     69 
     70 	KASSERTMSG(giantcnt > 0, "giantcnt=%d", giantcnt);
     71 	KASSERTMSG(curlwp == giantowner, "curlwp=%p giantowner=%p",
     72 	    curlwp, giantowner);
     73 	giantowner = NULL;
     74 	*nlocks = giantcnt;
     75 	giantcnt = 0;
     76 }
     77 
     78 void
     79 rump_kernel_bigunwrap(int nlocks)
     80 {
     81 
     82 	KASSERT(giantowner == NULL);
     83 	giantowner = curlwp;
     84 	giantcnt = nlocks;
     85 }
     86 
     87 void
     88 _kernel_lock(int nlocks)
     89 {
     90 	struct lwp *l = curlwp;
     91 
     92 	while (nlocks) {
     93 		if (giantowner == l) {
     94 			giantcnt += nlocks;
     95 			nlocks = 0;
     96 			ev_biglock_recurse.ev_count++;
     97 		} else {
     98 			if (rumpuser_mutex_tryenter(rump_giantlock) != 0) {
     99 				rump_unschedule_cpu1(l, NULL);
    100 				rumpuser_mutex_enter_nowrap(rump_giantlock);
    101 				rump_schedule_cpu(l);
    102 				ev_biglock_slow.ev_count++;
    103 			} else {
    104 				ev_biglock_fast.ev_count++;
    105 			}
    106 			giantowner = l;
    107 			giantcnt = 1;
    108 			nlocks--;
    109 		}
    110 	}
    111 }
    112 
    113 void
    114 _kernel_unlock(int nlocks, int *countp)
    115 {
    116 
    117 	if (giantowner != curlwp) {
    118 		KASSERT(nlocks == 0);
    119 		if (countp)
    120 			*countp = 0;
    121 		return;
    122 	}
    123 
    124 	if (countp)
    125 		*countp = giantcnt;
    126 	if (nlocks == 0)
    127 		nlocks = giantcnt;
    128 	if (nlocks == -1) {
    129 		KASSERT(giantcnt == 1);
    130 		nlocks = 1;
    131 	}
    132 	KASSERT(nlocks <= giantcnt);
    133 	while (nlocks--) {
    134 		giantcnt--;
    135 	}
    136 
    137 	if (giantcnt == 0) {
    138 		giantowner = NULL;
    139 		rumpuser_mutex_exit(rump_giantlock);
    140 	}
    141 }
    142 
    143 bool
    144 _kernel_locked_p(void)
    145 {
    146 
    147 	return giantowner == curlwp;
    148 }
    149 
    150 void
    151 rump_user_unschedule(int nlocks, int *countp, void *interlock)
    152 {
    153 
    154 	_kernel_unlock(nlocks, countp);
    155 	/*
    156 	 * XXX: technically we should unschedule_cpu1() here, but that
    157 	 * requires rump_intr_enter/exit to be implemented.
    158 	 */
    159 	rump_unschedule_cpu_interlock(curlwp, interlock);
    160 }
    161 
    162 void
    163 rump_user_schedule(int nlocks, void *interlock)
    164 {
    165 
    166 	rump_schedule_cpu_interlock(curlwp, interlock);
    167 
    168 	if (nlocks)
    169 		_kernel_lock(nlocks);
    170 }
    171