kern_kthread.c

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/*-
 * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
 * 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 AUTHOR 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/cpuset.h>
#include <sys/kthread.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/signalvar.h>
#include <sys/sx.h>
#include <sys/unistd.h>
#include <sys/wait.h>
#include <sys/sched.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>

#include <machine/stdarg.h>

/*
 * Start a kernel process.  This is called after a fork() call in
 * mi_startup() in the file kern/init_main.c.
 *
 * This function is used to start "internal" daemons and intended
 * to be called from SYSINIT().
 */
void
kproc_start(udata)
        const void *udata;
{
        const struct kproc_desc *kp = udata;
        int error;

        error = kproc_create((void (*)(void *))kp->func, NULL,
                    kp->global_procpp, 0, 0, "%s", kp->arg0);
        if (error)
                panic("kproc_start: %s: error %d", kp->arg0, error);
}

/*
 * Create a kernel process/thread/whatever.  It shares its address space
 * with proc0 - ie: kernel only.
 *
 * func is the function to start.
 * arg is the parameter to pass to function on first startup.
 * newpp is the return value pointing to the thread's struct proc.
 * flags are flags to fork1 (in unistd.h)
 * fmt and following will be *printf'd into (*newpp)->p_comm (for ps, etc.).
 */
int
kproc_create(void (*func)(void *), void *arg,
    struct proc **newpp, int flags, int pages, const char *fmt, ...)
{
        int error;
        va_list ap;
        struct thread *td;
        struct proc *p2;

        if (!proc0.p_stats)
                panic("kproc_create called too soon");

        error = fork1(&thread0, RFMEM | RFFDG | RFPROC | RFSTOPPED | flags,
            pages, &p2, NULL, 0);
        if (error)
                return error;

        /* save a global descriptor, if desired */
        if (newpp != NULL)
                *newpp = p2;

        /* this is a non-swapped system process */
        PROC_LOCK(p2);
        td = FIRST_THREAD_IN_PROC(p2);
        p2->p_flag |= P_SYSTEM | P_KTHREAD;
        td->td_pflags |= TDP_KTHREAD;
        mtx_lock(&p2->p_sigacts->ps_mtx);
        p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
        mtx_unlock(&p2->p_sigacts->ps_mtx);
        PROC_UNLOCK(p2);

        /* set up arg0 for 'ps', et al */
        va_start(ap, fmt);
        vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
        va_end(ap);
        /* set up arg0 for 'ps', et al */
        va_start(ap, fmt);
        vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
        va_end(ap);
#ifdef KTR
        sched_clear_tdname(td);
#endif

        /* call the processes' main()... */
        cpu_set_fork_handler(td, func, arg);

        /* Avoid inheriting affinity from a random parent. */
        cpuset_setthread(td->td_tid, cpuset_root);
        thread_lock(td);
        TD_SET_CAN_RUN(td);
        sched_prio(td, PVM);
        sched_user_prio(td, PUSER);

        /* Delay putting it on the run queue until now. */
        if (!(flags & RFSTOPPED))
                sched_add(td, SRQ_BORING); 
        thread_unlock(td);

        return 0;
}

void
kproc_exit(int ecode)
{
        struct thread *td;
        struct proc *p;

        td = curthread;
        p = td->td_proc;

        /*
         * Reparent curthread from proc0 to init so that the zombie
         * is harvested.
         */
        sx_xlock(&proctree_lock);
        PROC_LOCK(p);
        proc_reparent(p, initproc);
        PROC_UNLOCK(p);
        sx_xunlock(&proctree_lock);

        /*
         * Wakeup anyone waiting for us to exit.
         */
        wakeup(p);

        /* Buh-bye! */
        exit1(td, W_EXITCODE(ecode, 0));
}

/*
 * Advise a kernel process to suspend (or resume) in its main loop.
 * Participation is voluntary.
 */
int
kproc_suspend(struct proc *p, int timo)
{
        /*
         * Make sure this is indeed a system process and we can safely
         * use the p_siglist field.
         */
        PROC_LOCK(p);
        if ((p->p_flag & P_KTHREAD) == 0) {
                PROC_UNLOCK(p);
                return (EINVAL);
        }
        SIGADDSET(p->p_siglist, SIGSTOP);
        wakeup(p);
        return msleep(&p->p_siglist, &p->p_mtx, PPAUSE | PDROP, "suspkp", timo);
}

int
kproc_resume(struct proc *p)
{
        /*
         * Make sure this is indeed a system process and we can safely
         * use the p_siglist field.
         */
        PROC_LOCK(p);
        if ((p->p_flag & P_KTHREAD) == 0) {
                PROC_UNLOCK(p);
                return (EINVAL);
        }
        SIGDELSET(p->p_siglist, SIGSTOP);
        PROC_UNLOCK(p);
        wakeup(&p->p_siglist);
        return (0);
}

void
kproc_suspend_check(struct proc *p)
{
        PROC_LOCK(p);
        while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
                wakeup(&p->p_siglist);
                msleep(&p->p_siglist, &p->p_mtx, PPAUSE, "kpsusp", 0);
        }
        PROC_UNLOCK(p);
}


/*
 * Start a kernel thread.  
 *
 * This function is used to start "internal" daemons and intended
 * to be called from SYSINIT().
 */

void
kthread_start(udata)
        const void *udata;
{
        const struct kthread_desc       *kp = udata;
        int error;

        error = kthread_add((void (*)(void *))kp->func, NULL,
                    NULL, kp->global_threadpp, 0, 0, "%s", kp->arg0);
        if (error)
                panic("kthread_start: %s: error %d", kp->arg0, error);
}

/*
 * Create a kernel thread.  It shares its address space
 * with proc0 - ie: kernel only.
 *
 * func is the function to start.
 * arg is the parameter to pass to function on first startup.
 * newtdp is the return value pointing to the thread's struct thread.
 *  ** XXX fix this --> flags are flags to fork1 (in unistd.h) 
 * fmt and following will be *printf'd into (*newtd)->td_name (for ps, etc.).
 */
int
kthread_add(void (*func)(void *), void *arg, struct proc *p,
    struct thread **newtdp, int flags, int pages, const char *fmt, ...)
{
        va_list ap;
        struct thread *newtd, *oldtd;

        if (!proc0.p_stats)
                panic("kthread_add called too soon");

        /* If no process supplied, put it on proc0 */
        if (p == NULL)
                p = &proc0;

        /* Initialize our new td  */
        newtd = thread_alloc(pages);
        if (newtd == NULL)
                return (ENOMEM);

        PROC_LOCK(p);
        oldtd = FIRST_THREAD_IN_PROC(p);

        bzero(&newtd->td_startzero,
            __rangeof(struct thread, td_startzero, td_endzero));
/* XXX check if we should zero. */
        bcopy(&oldtd->td_startcopy, &newtd->td_startcopy,
            __rangeof(struct thread, td_startcopy, td_endcopy));

        /* set up arg0 for 'ps', et al */
        va_start(ap, fmt);
        vsnprintf(newtd->td_name, sizeof(newtd->td_name), fmt, ap);
        va_end(ap);

        newtd->td_proc = p;  /* needed for cpu_set_upcall */

        /* XXX optimise this probably? */
        /* On x86 (and probably the others too) it is way too full of junk */
        /* Needs a better name */
        cpu_set_upcall(newtd, oldtd);
        /* put the designated function(arg) as the resume context */
        cpu_set_fork_handler(newtd, func, arg);

        newtd->td_pflags |= TDP_KTHREAD;
        newtd->td_ucred = crhold(p->p_ucred);

        /* this code almost the same as create_thread() in kern_thr.c */
        p->p_flag |= P_HADTHREADS;
        newtd->td_sigmask = oldtd->td_sigmask; /* XXX dubious */
        thread_link(newtd, p);
        thread_lock(oldtd);
        /* let the scheduler know about these things. */
        sched_fork_thread(oldtd, newtd);
        TD_SET_CAN_RUN(newtd);
        thread_unlock(oldtd);
        PROC_UNLOCK(p);

        tidhash_add(newtd);

        /* Avoid inheriting affinity from a random parent. */
        cpuset_setthread(newtd->td_tid, cpuset_root);

        /* Delay putting it on the run queue until now. */
        if (!(flags & RFSTOPPED)) {
                thread_lock(newtd);
                sched_add(newtd, SRQ_BORING); 
                thread_unlock(newtd);
        }
        if (newtdp)
                *newtdp = newtd;
        return 0;
}

void
kthread_exit(void)
{
        struct proc *p;

        p = curthread->td_proc;

        /* A module may be waiting for us to exit. */
        wakeup(curthread);

        /*
         * The last exiting thread in a kernel process must tear down
         * the whole process.
         */
        rw_wlock(&tidhash_lock);
        PROC_LOCK(p);
        if (p->p_numthreads == 1) {
                PROC_UNLOCK(p);
                rw_wunlock(&tidhash_lock);
                kproc_exit(0);
        }
        LIST_REMOVE(curthread, td_hash);
        rw_wunlock(&tidhash_lock);
        PROC_SLOCK(p);
        thread_exit();
}

/*
 * Advise a kernel process to suspend (or resume) in its main loop.
 * Participation is voluntary.
 */
int
kthread_suspend(struct thread *td, int timo)
{
        struct proc *p;

        p = td->td_proc;

        /*
         * td_pflags should not be read by any thread other than
         * curthread, but as long as this flag is invariant during the
         * thread's lifetime, it is OK to check its state.
         */
        if ((td->td_pflags & TDP_KTHREAD) == 0)
                return (EINVAL);

        /*
         * The caller of the primitive should have already checked that the
         * thread is up and running, thus not being blocked by other
         * conditions.
         */
        PROC_LOCK(p);
        thread_lock(td);
        td->td_flags |= TDF_KTH_SUSP;
        thread_unlock(td);
        return (msleep(&td->td_flags, &p->p_mtx, PPAUSE | PDROP, "suspkt",
            timo));
}

/*
 * Resume a thread previously put asleep with kthread_suspend().
 */
int
kthread_resume(struct thread *td)
{
        struct proc *p;

        p = td->td_proc;

        /*
         * td_pflags should not be read by any thread other than
         * curthread, but as long as this flag is invariant during the
         * thread's lifetime, it is OK to check its state.
         */
        if ((td->td_pflags & TDP_KTHREAD) == 0)
                return (EINVAL);

        PROC_LOCK(p);
        thread_lock(td);
        td->td_flags &= ~TDF_KTH_SUSP;
        thread_unlock(td);
        wakeup(&td->td_flags);
        PROC_UNLOCK(p);
        return (0);
}

/*
 * Used by the thread to poll as to whether it should yield/sleep
 * and notify the caller that is has happened.
 */
void
kthread_suspend_check()
{
        struct proc *p;
        struct thread *td;

        td = curthread;
        p = td->td_proc;

        if ((td->td_pflags & TDP_KTHREAD) == 0)
                panic("%s: curthread is not a valid kthread", __func__);

        /*
         * As long as the double-lock protection is used when accessing the
         * TDF_KTH_SUSP flag, synchronizing the read operation via proc mutex
         * is fine.
         */
        PROC_LOCK(p);
        while (td->td_flags & TDF_KTH_SUSP) {
                wakeup(&td->td_flags);
                msleep(&td->td_flags, &p->p_mtx, PPAUSE, "ktsusp", 0);
        }
        PROC_UNLOCK(p);
}

int
kproc_kthread_add(void (*func)(void *), void *arg,
            struct proc **procptr, struct thread **tdptr,
            int flags, int pages, const char *procname, const char *fmt, ...) 
{
        int error;
        va_list ap;
        char buf[100];
        struct thread *td;

        if (*procptr == 0) {
                error = kproc_create(func, arg,
                        procptr, flags, pages, "%s", procname);
                if (error)
                        return (error);
                td = FIRST_THREAD_IN_PROC(*procptr);
                if (tdptr)
                        *tdptr = td;
                va_start(ap, fmt);
                vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
                va_end(ap);
#ifdef KTR
                sched_clear_tdname(td);
#endif
                return (0); 
        }
        va_start(ap, fmt);
        vsnprintf(buf, sizeof(buf), fmt, ap);
        va_end(ap);
        error = kthread_add(func, arg, *procptr,
                    tdptr, flags, pages, "%s", buf);
        return (error);
}