sys/kern/subr_cpuhelper.c

   1 /*
   2  * Copyright (c) 2017 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Sepherosa Ziehau <sepherosa@gmail.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/param.h>
  36 #include <sys/systm.h>
  37 #include <sys/kernel.h>
  38 #include <sys/thread.h>
  39
  40 #include <sys/cpuhelper.h>
  41
  42 static struct thread    *cpuhelper[MAXCPU];
  43 static int              (*cpuhelper_saved_putport)(lwkt_port_t, lwkt_msg_t);
  44
  45 static __inline lwkt_port_t
  46 cpuhelper_port(int cpuid)
  47 {
  48
  49         return (&cpuhelper[cpuid]->td_msgport);
  50 }
  51
  52 /*
  53  * To prevent deadlocking, we must execute these self-referential messages
  54  * synchronously, effectively turning the message into a direct procedure
  55  * call.
  56  */
  57 static int
  58 cpuhelper_putport(lwkt_port_t port, lwkt_msg_t lmsg)
  59 {
  60         struct cpuhelper_msg *msg = (struct cpuhelper_msg *)lmsg;
  61
  62
  63         if ((lmsg->ms_flags & MSGF_SYNC) && port == &curthread->td_msgport) {
  64                 msg->ch_cb(msg);
  65                 return (EASYNC);
  66         } else {
  67                 return (cpuhelper_saved_putport(port, lmsg));
  68         }
  69 }
  70
  71 static void
  72 cpuhelper_mainloop(void *arg __unused)
  73 {
  74         struct cpuhelper_msg *msg;
  75
  76
  77         while ((msg = lwkt_waitport(&curthread->td_msgport, 0))) {
  78                 KASSERT(msg->ch_cb != NULL, ("cpuhelper%d: badmsg", mycpuid));
  79                 msg->ch_cb(msg);
  80         }
  81         /* NEVER REACHED */
  82 }
  83
  84 void
  85 cpuhelper_initmsg(struct cpuhelper_msg *msg, lwkt_port_t rport,
  86     cpuhelper_cb_t cb, void *cbarg, int flags)
  87 {
  88
  89         lwkt_initmsg(&msg->ch_lmsg, rport, flags);
  90         msg->ch_cb = cb;
  91         msg->ch_cbarg = cbarg;
  92         msg->ch_cbarg1 = 0;
  93 }
  94
  95 void
  96 cpuhelper_replymsg(struct cpuhelper_msg *msg, int error)
  97 {
  98
  99         lwkt_replymsg(&msg->ch_lmsg, error);
 100 }
 101
 102 int
 103 cpuhelper_domsg(struct cpuhelper_msg *msg, int cpuid)
 104 {
 105
 106         KASSERT(cpuid >= 0 && cpuid < ncpus, ("invalid cpuid"));
 107         return (lwkt_domsg(cpuhelper_port(cpuid), &msg->ch_lmsg, 0));
 108 }
 109
 110 void
 111 cpuhelper_assert(int cpuid, bool in)
 112 {
 113
 114 #ifdef INVARIANTS
 115         KASSERT(cpuid >= 0 && cpuid < ncpus, ("invalid cpuid"));
 116         if (in) {
 117                 KASSERT(&curthread->td_msgport == cpuhelper_port(cpuid),
 118                     ("not in cpuhelper%d", cpuid));
 119         } else {
 120                 KASSERT(&curthread->td_msgport != cpuhelper_port(cpuid),
 121                     ("in cpuhelper%d", cpuid));
 122         }
 123 #endif
 124 }
 125
 126 static void
 127 cpuhelper_init(void)
 128 {
 129         int i;
 130
 131         /*
 132          * Create per-cpu helper threads.
 133          */
 134         for (i = 0; i < ncpus; ++i) {
 135                 lwkt_port_t port;
 136
 137                 lwkt_create(cpuhelper_mainloop, NULL, &cpuhelper[i], NULL,
 138                     TDF_NOSTART|TDF_FORCE_SPINPORT|TDF_FIXEDCPU, i,
 139                     "cpuhelper %d", i);
 140
 141                 /*
 142                  * Override the putport function.  Our custom function checks
 143                  * for self-references.
 144                  */
 145                 port = cpuhelper_port(i);
 146                 if (cpuhelper_saved_putport == NULL)
 147                         cpuhelper_saved_putport = port->mp_putport;
 148                 KKASSERT(cpuhelper_saved_putport == port->mp_putport);
 149                 port->mp_putport = cpuhelper_putport;
 150
 151                 lwkt_schedule(cpuhelper[i]);
 152         }
 153 }
 154 SYSINIT(cpuhelper, SI_SUB_PRE_DRIVERS, SI_ORDER_FIRST, cpuhelper_init, NULL);