FreeBSD/Linux Kernel Cross Reference
sys/sys/userret.h

     /*      $NetBSD: userret.h,v 1.33 2020/03/26 20:19:06 ad Exp $  */
     
     /*-
      * Copyright (c) 1998, 2000, 2003, 2006, 2008, 2019, 2020
      *     The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Charles M. Hannum, and Andrew Doran.
     *
     * 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.
     */
    
    /*-
     * Copyright (c) 1990 The Regents of the University of California.
     * All rights reserved.
     *
     * This code is derived from software contributed to Berkeley by
     * William Jolitz.
     *
     * 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.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
     *
     */
    
    #ifndef _SYS_USERRET_H_
    #define _SYS_USERRET_H_
    
    #include <sys/lockdebug.h>
    #include <sys/intr.h>
    #include <sys/psref.h>
    
    /*
     * Define the MI code needed before returning to user mode, for trap and
     * syscall.
     *
     * We handle "exceptional" events: pending signals, stop/exit actions, etc. 
     * Note that the event must be flagged BEFORE any AST is posted as we are
     * reading unlocked.
     */
    static __inline void
    mi_userret(struct lwp *l)
    {
            struct cpu_info *ci;
    
            KPREEMPT_DISABLE(l);
            ci = l->l_cpu;
            KASSERTMSG(ci->ci_biglock_count == 0, "kernel_lock leaked");
            KASSERT(l->l_blcnt == 0);
            if (__predict_false(ci->ci_want_resched)) {
                    preempt();
                    ci = l->l_cpu;
            }
            if (__predict_false(l->l_flag & LW_USERRET)) {
                    KPREEMPT_ENABLE(l);
                    lwp_userret(l);
                    KPREEMPT_DISABLE(l);
                    ci = l->l_cpu;
            }
           /*
            * lwp_eprio() is too involved to use here unlocked.  At this point
            * it only matters for PTHREAD_PRIO_PROTECT; setting a too low value
            * is OK because the scheduler will find out the true value if we
            * end up in mi_switch().
            *
            * This is being called on every syscall and trap, and remote CPUs
            * regularly look at ci_schedstate.  Keep the cache line in the
            * SHARED state by only updating spc_curpriority if it has changed.
            */
           l->l_kpriority = false;
           if (ci->ci_schedstate.spc_curpriority != l->l_priority) {
                   ci->ci_schedstate.spc_curpriority = l->l_priority;
           }
           KPREEMPT_ENABLE(l);
   
           LOCKDEBUG_BARRIER(NULL, 0);
           KASSERT(l->l_nopreempt == 0);
           PSREF_DEBUG_BARRIER();
           KASSERT(l->l_psrefs == 0);
   }
   
   #endif  /* !_SYS_USERRET_H_ */

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