FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_pserialize.c

     /*      $NetBSD: subr_pserialize.c,v 1.19 2022/11/15 10:29:56 macallan Exp $    */
     
     /*-
      * Copyright (c) 2010, 2011 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     * POSSIBILITY OF SUCH DAMAGE.
     */
    
    /*
     * Passive serialization.
     */
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: subr_pserialize.c,v 1.19 2022/11/15 10:29:56 macallan Exp $");
    
    #include <sys/param.h>
    #include <sys/atomic.h>
    #include <sys/cpu.h>
    #include <sys/kernel.h>
    #include <sys/evcnt.h>
    #include <sys/kmem.h>
    #include <sys/mutex.h>
    #include <sys/pserialize.h>
    #include <sys/xcall.h>
    
    struct pserialize {
            char                    psz_dummy;
    };
    
    static kmutex_t                 psz_lock        __cacheline_aligned;
    static struct evcnt             psz_ev_excl     __cacheline_aligned =
        EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "pserialize", "exclusive access");
    EVCNT_ATTACH_STATIC(psz_ev_excl);
    
    /*
     * pserialize_init:
     *
     *      Initialize passive serialization structures.
     */
    void
    pserialize_init(void)
    {
    
            mutex_init(&psz_lock, MUTEX_DEFAULT, IPL_NONE);
    }
    
    /*
     * pserialize_create:
     *
     *      Create and initialize a passive serialization object.
     */
    pserialize_t
    pserialize_create(void)
    {
            pserialize_t psz;
    
            psz = kmem_zalloc(sizeof(*psz), KM_SLEEP);
            return psz;
    }
    
    /*
     * pserialize_destroy:
     *
     *      Destroy a passive serialization object.
     */
    void
    pserialize_destroy(pserialize_t psz)
    {
    
            kmem_free(psz, sizeof(*psz));
    }
    
    /*
     * pserialize_perform:
     *
     *      Perform the write side of passive serialization.
     */
    void
    pserialize_perform(pserialize_t psz)
   {
   
           KASSERT(!cpu_intr_p());
           KASSERT(!cpu_softintr_p());
   
           if (__predict_false(panicstr != NULL)) {
                   return;
           }
   
           if (__predict_false(mp_online == false)) {
                   psz_ev_excl.ev_count++;
                   return;
           }
   
           /*
            * Broadcast a NOP to all CPUs and wait until all of them complete.
            */
           xc_barrier(XC_HIGHPRI);
   
           mutex_enter(&psz_lock);
           psz_ev_excl.ev_count++;
           mutex_exit(&psz_lock);
   }
   
   int
   pserialize_read_enter(void)
   {
           int s;
   
           s = splsoftserial();
           curcpu()->ci_psz_read_depth++;
           __insn_barrier();
           return s;
   }
   
   void
   pserialize_read_exit(int s)
   {
   
           KASSERT((cold || kpreempt_disabled()));
   
           __insn_barrier();
           if (__predict_false(curcpu()->ci_psz_read_depth-- == 0))
                   panic("mismatching pserialize_read_exit()");
           splx(s);
   }
   
   /*
    * pserialize_in_read_section:
    *
    *      True if the caller is in a pserialize read section.  To be used
    *      only for diagnostic assertions where we want to guarantee the
    *      condition like:
    *
    *              KASSERT(pserialize_in_read_section());
    */
   bool
   pserialize_in_read_section(void)
   {
   
           return kpreempt_disabled() && curcpu()->ci_psz_read_depth > 0;
   }
   
   /*
    * pserialize_not_in_read_section:
    *
    *      True if the caller is not in a pserialize read section.  To be
    *      used only for diagnostic assertions where we want to guarantee
    *      the condition like:
    *
    *              KASSERT(pserialize_not_in_read_section());
    */
   bool
   pserialize_not_in_read_section(void)
   {
           bool notin;
   
           kpreempt_disable();
           notin = (curcpu()->ci_psz_read_depth == 0);
           kpreempt_enable();
   
           return notin;
   }

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