freebsd-dev/sys/kern/kern_thread.c
Julian Elischer 48bfcddd94 Round out the facilty for a 'bound' thread to loan out its KSE
in specific situations. The owner thread must be blocked, and the
borrower can not proceed back to user space with the borrowed KSE.
The borrower will return the KSE on the next context switch where
teh owner wants it back. This removes a lot of possible
race conditions and deadlocks. It is consceivable that the
borrower should inherit the priority of the owner too.
that's another discussion and would be simple to do.

Also, as part of this, the "preallocatd spare thread" is attached to the
thread doing a syscall rather than the KSE. This removes the need to lock
the scheduler when we want to access it, as it's now "at hand".

DDB now shows a lot mor info for threaded proceses though it may need
some optimisation to squeeze it all back into 80 chars again.
(possible JKH project)

Upcalls are now "bound" threads, but "KSE Lending" now means that
other completing syscalls can be completed using that KSE before the upcall
finally makes it back to the UTS. (getting threads OUT OF THE KERNEL is
one of the highest priorities in the KSE system.) The upcall when it happens
will present all the completed syscalls to the KSE for selection.
2002-10-09 02:33:36 +00:00

1172 lines
30 KiB
C

/*
* Copyright (C) 2001 Julian Elischer <julian@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(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/filedesc.h>
#include <sys/tty.h>
#include <sys/signalvar.h>
#include <sys/sx.h>
#include <sys/user.h>
#include <sys/jail.h>
#include <sys/kse.h>
#include <sys/ktr.h>
#include <sys/ucontext.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/pmap.h>
#include <vm/uma.h>
#include <vm/vm_map.h>
#include <machine/frame.h>
/*
* KSEGRP related storage.
*/
static uma_zone_t ksegrp_zone;
static uma_zone_t kse_zone;
static uma_zone_t thread_zone;
/* DEBUG ONLY */
SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
static int oiks_debug = 1; /* 0 disable, 1 printf, 2 enter debugger */
SYSCTL_INT(_kern_threads, OID_AUTO, oiks, CTLFLAG_RW,
&oiks_debug, 0, "OIKS thread debug");
static int max_threads_per_proc = 10;
SYSCTL_INT(_kern_threads, OID_AUTO, max_per_proc, CTLFLAG_RW,
&max_threads_per_proc, 0, "Limit on threads per proc");
#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
struct threadqueue zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
struct mtx zombie_thread_lock;
MTX_SYSINIT(zombie_thread_lock, &zombie_thread_lock,
"zombie_thread_lock", MTX_SPIN);
/*
* Pepare a thread for use.
*/
static void
thread_ctor(void *mem, int size, void *arg)
{
struct thread *td;
KASSERT((size == sizeof(struct thread)),
("size mismatch: %d != %d\n", size, (int)sizeof(struct thread)));
td = (struct thread *)mem;
td->td_state = TDS_INACTIVE;
td->td_flags |= TDF_UNBOUND;
}
/*
* Reclaim a thread after use.
*/
static void
thread_dtor(void *mem, int size, void *arg)
{
struct thread *td;
KASSERT((size == sizeof(struct thread)),
("size mismatch: %d != %d\n", size, (int)sizeof(struct thread)));
td = (struct thread *)mem;
#ifdef INVARIANTS
/* Verify that this thread is in a safe state to free. */
switch (td->td_state) {
case TDS_INHIBITED:
case TDS_RUNNING:
case TDS_CAN_RUN:
case TDS_RUNQ:
/*
* We must never unlink a thread that is in one of
* these states, because it is currently active.
*/
panic("bad state for thread unlinking");
/* NOTREACHED */
case TDS_INACTIVE:
break;
default:
panic("bad thread state");
/* NOTREACHED */
}
#endif
}
/*
* Initialize type-stable parts of a thread (when newly created).
*/
static void
thread_init(void *mem, int size)
{
struct thread *td;
KASSERT((size == sizeof(struct thread)),
("size mismatch: %d != %d\n", size, (int)sizeof(struct thread)));
td = (struct thread *)mem;
mtx_lock(&Giant);
pmap_new_thread(td, 0);
mtx_unlock(&Giant);
cpu_thread_setup(td);
}
/*
* Tear down type-stable parts of a thread (just before being discarded).
*/
static void
thread_fini(void *mem, int size)
{
struct thread *td;
KASSERT((size == sizeof(struct thread)),
("size mismatch: %d != %d\n", size, (int)sizeof(struct thread)));
td = (struct thread *)mem;
pmap_dispose_thread(td);
}
/*
* Fill a ucontext_t with a thread's context information.
*
* This is an analogue to getcontext(3).
*/
void
thread_getcontext(struct thread *td, ucontext_t *uc)
{
/*
* XXX this is declared in a MD include file, i386/include/ucontext.h but
* is used in MI code.
*/
#ifdef __i386__
get_mcontext(td, &uc->uc_mcontext);
#endif
uc->uc_sigmask = td->td_proc->p_sigmask;
}
/*
* Set a thread's context from a ucontext_t.
*
* This is an analogue to setcontext(3).
*/
int
thread_setcontext(struct thread *td, ucontext_t *uc)
{
int ret;
/*
* XXX this is declared in a MD include file, i386/include/ucontext.h but
* is used in MI code.
*/
#ifdef __i386__
ret = set_mcontext(td, &uc->uc_mcontext);
#else
ret = ENOSYS;
#endif
if (ret == 0) {
SIG_CANTMASK(uc->uc_sigmask);
PROC_LOCK(td->td_proc);
td->td_proc->p_sigmask = uc->uc_sigmask;
PROC_UNLOCK(td->td_proc);
}
return (ret);
}
/*
* Initialize global thread allocation resources.
*/
void
threadinit(void)
{
#ifndef __ia64__
thread_zone = uma_zcreate("THREAD", sizeof (struct thread),
thread_ctor, thread_dtor, thread_init, thread_fini,
UMA_ALIGN_CACHE, 0);
#else
/*
* XXX the ia64 kstack allocator is really lame and is at the mercy
* of contigmallloc(). This hackery is to pre-construct a whole
* pile of thread structures with associated kernel stacks early
* in the system startup while contigmalloc() still works. Once we
* have them, keep them. Sigh.
*/
thread_zone = uma_zcreate("THREAD", sizeof (struct thread),
thread_ctor, thread_dtor, thread_init, thread_fini,
UMA_ALIGN_CACHE, UMA_ZONE_NOFREE);
uma_prealloc(thread_zone, 512); /* XXX arbitary */
#endif
ksegrp_zone = uma_zcreate("KSEGRP", sizeof (struct ksegrp),
NULL, NULL, NULL, NULL,
UMA_ALIGN_CACHE, 0);
kse_zone = uma_zcreate("KSE", sizeof (struct kse),
NULL, NULL, NULL, NULL,
UMA_ALIGN_CACHE, 0);
}
/*
* Stash an embarasingly extra thread into the zombie thread queue.
*/
void
thread_stash(struct thread *td)
{
mtx_lock_spin(&zombie_thread_lock);
TAILQ_INSERT_HEAD(&zombie_threads, td, td_runq);
mtx_unlock_spin(&zombie_thread_lock);
}
/*
* Reap zombie threads.
*/
void
thread_reap(void)
{
struct thread *td_reaped;
/*
* don't even bother to lock if none at this instant
* We really don't care about the next instant..
*/
if (!TAILQ_EMPTY(&zombie_threads)) {
mtx_lock_spin(&zombie_thread_lock);
while (!TAILQ_EMPTY(&zombie_threads)) {
td_reaped = TAILQ_FIRST(&zombie_threads);
TAILQ_REMOVE(&zombie_threads, td_reaped, td_runq);
mtx_unlock_spin(&zombie_thread_lock);
thread_free(td_reaped);
mtx_lock_spin(&zombie_thread_lock);
}
mtx_unlock_spin(&zombie_thread_lock);
}
}
/*
* Allocate a ksegrp.
*/
struct ksegrp *
ksegrp_alloc(void)
{
return (uma_zalloc(ksegrp_zone, M_WAITOK));
}
/*
* Allocate a kse.
*/
struct kse *
kse_alloc(void)
{
return (uma_zalloc(kse_zone, M_WAITOK));
}
/*
* Allocate a thread.
*/
struct thread *
thread_alloc(void)
{
thread_reap(); /* check if any zombies to get */
return (uma_zalloc(thread_zone, M_WAITOK));
}
/*
* Deallocate a ksegrp.
*/
void
ksegrp_free(struct ksegrp *td)
{
uma_zfree(ksegrp_zone, td);
}
/*
* Deallocate a kse.
*/
void
kse_free(struct kse *td)
{
uma_zfree(kse_zone, td);
}
/*
* Deallocate a thread.
*/
void
thread_free(struct thread *td)
{
uma_zfree(thread_zone, td);
}
/*
* Store the thread context in the UTS's mailbox.
* then add the mailbox at the head of a list we are building in user space.
* The list is anchored in the ksegrp structure.
*/
int
thread_export_context(struct thread *td)
{
struct proc *p;
struct ksegrp *kg;
uintptr_t mbx;
void *addr;
int error;
ucontext_t uc;
p = td->td_proc;
kg = td->td_ksegrp;
/* Export the user/machine context. */
#if 0
addr = (caddr_t)td->td_mailbox +
offsetof(struct kse_thr_mailbox, tm_context);
#else /* if user pointer arithmetic is valid in the kernel */
addr = (void *)(&td->td_mailbox->tm_context);
#endif
error = copyin(addr, &uc, sizeof(ucontext_t));
if (error == 0) {
thread_getcontext(td, &uc);
error = copyout(&uc, addr, sizeof(ucontext_t));
}
if (error) {
PROC_LOCK(p);
psignal(p, SIGSEGV);
PROC_UNLOCK(p);
return (error);
}
/* get address in latest mbox of list pointer */
#if 0
addr = (caddr_t)td->td_mailbox
+ offsetof(struct kse_thr_mailbox , tm_next);
#else /* if user pointer arithmetic is valid in the kernel */
addr = (void *)(&td->td_mailbox->tm_next);
#endif
/*
* Put the saved address of the previous first
* entry into this one
*/
for (;;) {
mbx = (uintptr_t)kg->kg_completed;
if (suword(addr, mbx)) {
PROC_LOCK(p);
psignal(p, SIGSEGV);
PROC_UNLOCK(p);
return (EFAULT);
}
PROC_LOCK(p);
if (mbx == (uintptr_t)kg->kg_completed) {
kg->kg_completed = td->td_mailbox;
PROC_UNLOCK(p);
break;
}
PROC_UNLOCK(p);
}
return (0);
}
/*
* Take the list of completed mailboxes for this KSEGRP and put them on this
* KSE's mailbox as it's the next one going up.
*/
static int
thread_link_mboxes(struct ksegrp *kg, struct kse *ke)
{
struct proc *p = kg->kg_proc;
void *addr;
uintptr_t mbx;
#if 0
addr = (caddr_t)ke->ke_mailbox
+ offsetof(struct kse_mailbox, km_completed);
#else /* if user pointer arithmetic is valid in the kernel */
addr = (void *)(&ke->ke_mailbox->km_completed);
#endif
for (;;) {
mbx = (uintptr_t)kg->kg_completed;
if (suword(addr, mbx)) {
PROC_LOCK(p);
psignal(p, SIGSEGV);
PROC_UNLOCK(p);
return (EFAULT);
}
/* XXXKSE could use atomic CMPXCH here */
PROC_LOCK(p);
if (mbx == (uintptr_t)kg->kg_completed) {
kg->kg_completed = NULL;
PROC_UNLOCK(p);
break;
}
PROC_UNLOCK(p);
}
return (0);
}
/*
* Discard the current thread and exit from its context.
*
* Because we can't free a thread while we're operating under its context,
* push the current thread into our KSE's ke_tdspare slot, freeing the
* thread that might be there currently. Because we know that only this
* processor will run our KSE, we needn't worry about someone else grabbing
* our context before we do a cpu_throw.
*/
void
thread_exit(void)
{
struct thread *td;
struct kse *ke;
struct proc *p;
struct ksegrp *kg;
td = curthread;
kg = td->td_ksegrp;
p = td->td_proc;
ke = td->td_kse;
mtx_assert(&sched_lock, MA_OWNED);
KASSERT(p != NULL, ("thread exiting without a process"));
KASSERT(ke != NULL, ("thread exiting without a kse"));
KASSERT(kg != NULL, ("thread exiting without a kse group"));
PROC_LOCK_ASSERT(p, MA_OWNED);
CTR1(KTR_PROC, "thread_exit: thread %p", td);
KASSERT(!mtx_owned(&Giant), ("dying thread owns giant"));
if (ke->ke_tdspare != NULL) {
thread_stash(ke->ke_tdspare);
ke->ke_tdspare = NULL;
}
if (td->td_standin != NULL) {
thread_stash(td->td_standin);
td->td_standin = NULL;
}
cpu_thread_exit(td); /* XXXSMP */
/*
* The last thread is left attached to the process
* So that the whole bundle gets recycled. Skip
* all this stuff.
*/
if (p->p_numthreads > 1) {
/* Unlink this thread from its proc. and the kseg */
TAILQ_REMOVE(&p->p_threads, td, td_plist);
p->p_numthreads--;
TAILQ_REMOVE(&kg->kg_threads, td, td_kglist);
kg->kg_numthreads--;
/*
* The test below is NOT true if we are the
* sole exiting thread. P_STOPPED_SNGL is unset
* in exit1() after it is the only survivor.
*/
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount) {
thread_unsuspend_one(p->p_singlethread);
}
}
/* Reassign this thread's KSE. */
ke->ke_thread = NULL;
td->td_kse = NULL;
ke->ke_state = KES_UNQUEUED;
if (ke->ke_bound == td) {
printf("thread_exit: entered with ke_bound set\n");
ke->ke_bound = NULL; /* should never happen */
}
kse_reassign(ke);
PROC_UNLOCK(p);
td->td_state = TDS_INACTIVE;
td->td_proc = NULL;
td->td_ksegrp = NULL;
td->td_last_kse = NULL;
/*
* For now stash this here, however
* it's not a permanent solution.
* When we want to make KSEs exit as well
* we'll have to face this one again.
* Where will we hide it then?
*
* In borrower threads, stash it in the lender
* Where it won't be needed until
* this thread is long gone.
*/
if (ke->ke_bound) {
if (ke->ke_bound->td_standin) {
thread_stash(ke->ke_bound->td_standin);
}
ke->ke_bound->td_standin = td;
} else {
ke->ke_tdspare = td;
}
} else {
PROC_UNLOCK(p);
}
cpu_throw();
/* NOTREACHED */
}
/*
* Link a thread to a process.
* set up anything that needs to be initialized for it to
* be used by the process.
*
* Note that we do not link to the proc's ucred here.
* The thread is linked as if running but no KSE assigned.
*/
void
thread_link(struct thread *td, struct ksegrp *kg)
{
struct proc *p;
p = kg->kg_proc;
td->td_state = TDS_INACTIVE;
td->td_proc = p;
td->td_ksegrp = kg;
td->td_last_kse = NULL;
LIST_INIT(&td->td_contested);
callout_init(&td->td_slpcallout, 1);
TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
TAILQ_INSERT_HEAD(&kg->kg_threads, td, td_kglist);
p->p_numthreads++;
kg->kg_numthreads++;
if (oiks_debug && p->p_numthreads > max_threads_per_proc) {
printf("OIKS %d\n", p->p_numthreads);
if (oiks_debug > 1)
Debugger("OIKS");
}
td->td_kse = NULL;
}
/*
* Create a thread and schedule it for upcall on the KSE given.
*/
struct thread *
thread_schedule_upcall(struct thread *td, struct kse *ke)
{
struct thread *td2;
int newkse;
mtx_assert(&sched_lock, MA_OWNED);
newkse = (ke != td->td_kse);
/*
* If the kse is already owned by another thread then we can't
* schedule an upcall because the other thread must be BOUND
* which means it is not in a position to take an upcall.
* We must be borrowing the KSE to allow us to complete some in-kernel
* work. When we complete, the Bound thread will have teh chance to
* complete. This thread will sleep as planned. Hopefully there will
* eventually be un unbound thread that can be converted to an
* upcall to report the completion of this thread.
*/
if (ke->ke_bound && ((ke->ke_bound->td_flags & TDF_UNBOUND) == 0)) {
return (NULL);
}
KASSERT((ke->ke_bound == NULL), ("kse already bound"));
if ((td2 = td->td_standin) != NULL) {
td->td_standin = NULL;
} else {
if (newkse)
panic("no reserve thread when called with a new kse");
/*
* If called from (e.g.) sleep and we do not have
* a reserve thread, then we've used it, so do not
* create an upcall.
*/
return(NULL);
}
CTR3(KTR_PROC, "thread_schedule_upcall: thread %p (pid %d, %s)",
td2, td->td_proc->p_pid, td->td_proc->p_comm);
bzero(&td2->td_startzero,
(unsigned)RANGEOF(struct thread, td_startzero, td_endzero));
bcopy(&td->td_startcopy, &td2->td_startcopy,
(unsigned) RANGEOF(struct thread, td_startcopy, td_endcopy));
thread_link(td2, ke->ke_ksegrp);
cpu_set_upcall(td2, td->td_pcb);
/*
* XXXKSE do we really need this? (default values for the
* frame).
*/
bcopy(td->td_frame, td2->td_frame, sizeof(struct trapframe));
/*
* Bind the new thread to the KSE,
* and if it's our KSE, lend it back to ourself
* so we can continue running.
*/
td2->td_ucred = crhold(td->td_ucred);
td2->td_flags = TDF_UPCALLING; /* note: BOUND */
td2->td_kse = ke;
td2->td_state = TDS_CAN_RUN;
td2->td_inhibitors = 0;
/*
* If called from msleep(), we are working on the current
* KSE so fake that we borrowed it. If called from
* kse_create(), don't, as we have a new kse too.
*/
if (!newkse) {
/*
* This thread will be scheduled when the current thread
* blocks, exits or tries to enter userspace, (which ever
* happens first). When that happens the KSe will "revert"
* to this thread in a BOUND manner. Since we are called
* from msleep() this is going to be "very soon" in nearly
* all cases.
*/
ke->ke_bound = td2;
TD_SET_LOAN(td2);
} else {
ke->ke_bound = NULL;
ke->ke_thread = td2;
setrunqueue(td2);
}
return (td2); /* bogus.. should be a void function */
}
/*
* Schedule an upcall to notify a KSE process recieved signals.
*
* XXX - Modifying a sigset_t like this is totally bogus.
*/
struct thread *
signal_upcall(struct proc *p, int sig)
{
struct thread *td, *td2;
struct kse *ke;
sigset_t ss;
int error;
PROC_LOCK_ASSERT(p, MA_OWNED);
return (NULL);
td = FIRST_THREAD_IN_PROC(p);
ke = td->td_kse;
PROC_UNLOCK(p);
error = copyin(&ke->ke_mailbox->km_sigscaught, &ss, sizeof(sigset_t));
PROC_LOCK(p);
if (error)
return (NULL);
SIGADDSET(ss, sig);
PROC_UNLOCK(p);
error = copyout(&ss, &ke->ke_mailbox->km_sigscaught, sizeof(sigset_t));
PROC_LOCK(p);
if (error)
return (NULL);
if (td->td_standin == NULL)
td->td_standin = thread_alloc();
mtx_lock_spin(&sched_lock);
td2 = thread_schedule_upcall(td, ke); /* Bogus JRE */
mtx_unlock_spin(&sched_lock);
return (td2);
}
/*
* The extra work we go through if we are a threaded process when we
* return to userland.
*
* If we are a KSE process and returning to user mode, check for
* extra work to do before we return (e.g. for more syscalls
* to complete first). If we were in a critical section, we should
* just return to let it finish. Same if we were in the UTS (in
* which case the mailbox's context's busy indicator will be set).
* The only traps we suport will have set the mailbox.
* We will clear it here.
*/
int
thread_userret(struct thread *td, struct trapframe *frame)
{
int error;
int unbound;
struct kse *ke;
struct ksegrp *kg;
struct thread *td2;
struct proc *p;
error = 0;
unbound = td->td_flags & TDF_UNBOUND;
kg = td->td_ksegrp;
p = td->td_proc;
/*
* Originally bound threads never upcall but they may
* loan out their KSE at this point.
* Upcalls imply bound.. They also may want to do some Philantropy.
* Unbound threads on the other hand either yield to other work
* or transform into an upcall.
* (having saved their context to user space in both cases)
*/
if (unbound ) {
/*
* We are an unbound thread, looking to return to
* user space.
* THere are several possibilities:
* 1) we are using a borrowed KSE. save state and exit.
* kse_reassign() will recycle the kse as needed,
* 2) we are not.. save state, and then convert ourself
* to be an upcall, bound to the KSE.
* if there are others that need the kse,
* give them a chance by doing an mi_switch().
* Because we are bound, control will eventually return
* to us here.
* ***
* Save the thread's context, and link it
* into the KSEGRP's list of completed threads.
*/
error = thread_export_context(td);
td->td_mailbox = NULL;
if (error) {
/*
* If we are not running on a borrowed KSE, then
* failing to do the KSE operation just defaults
* back to synchonous operation, so just return from
* the syscall. If it IS borrowed, there is nothing
* we can do. We just lose that context. We
* probably should note this somewhere and send
* the process a signal.
*/
PROC_LOCK(td->td_proc);
psignal(td->td_proc, SIGSEGV);
mtx_lock_spin(&sched_lock);
if (td->td_kse->ke_bound == NULL) {
td->td_flags &= ~TDF_UNBOUND;
PROC_UNLOCK(td->td_proc);
mtx_unlock_spin(&sched_lock);
return (error); /* go sync */
}
thread_exit();
}
/*
* if the KSE is owned and we are borrowing it,
* don't make an upcall, just exit so that the owner
* can get its KSE if it wants it.
* Our context is already safely stored for later
* use by the UTS.
*/
PROC_LOCK(p);
mtx_lock_spin(&sched_lock);
if (td->td_kse->ke_bound) {
thread_exit();
}
PROC_UNLOCK(p);
/*
* Turn ourself into a bound upcall.
* We will rely on kse_reassign()
* to make us run at a later time.
* We should look just like a sheduled upcall
* from msleep() or cv_wait().
*/
td->td_flags &= ~TDF_UNBOUND;
td->td_flags |= TDF_UPCALLING;
/* Only get here if we have become an upcall */
} else {
mtx_lock_spin(&sched_lock);
}
/*
* We ARE going back to userland with this KSE.
* Check for threads that need to borrow it.
* Optimisation: don't call mi_switch if no-one wants the KSE.
* Any other thread that comes ready after this missed the boat.
*/
ke = td->td_kse;
if ((td2 = kg->kg_last_assigned))
td2 = TAILQ_NEXT(td2, td_runq);
else
td2 = TAILQ_FIRST(&kg->kg_runq);
if (td2) {
/*
* force a switch to more urgent 'in kernel'
* work. Control will return to this thread
* when there is no more work to do.
* kse_reassign() will do tha for us.
*/
TD_SET_LOAN(td);
ke->ke_bound = td;
ke->ke_thread = NULL;
mi_switch(); /* kse_reassign() will (re)find td2 */
}
mtx_unlock_spin(&sched_lock);
/*
* Optimisation:
* Ensure that we have a spare thread available,
* for when we re-enter the kernel.
*/
if (td->td_standin == NULL) {
if (ke->ke_tdspare) {
td->td_standin = ke->ke_tdspare;
ke->ke_tdspare = NULL;
} else {
td->td_standin = thread_alloc();
}
}
/*
* To get here, we know there is no other need for our
* KSE so we can proceed. If not upcalling, go back to
* userspace. If we are, get the upcall set up.
*/
if ((td->td_flags & TDF_UPCALLING) == 0)
return (0);
/*
* We must be an upcall to get this far.
* There is no more work to do and we are going to ride
* this thead/KSE up to userland as an upcall.
* Do the last parts of the setup needed for the upcall.
*/
CTR3(KTR_PROC, "userret: upcall thread %p (pid %d, %s)",
td, td->td_proc->p_pid, td->td_proc->p_comm);
/*
* Set user context to the UTS.
*/
cpu_set_upcall_kse(td, ke);
/*
* Put any completed mailboxes on this KSE's list.
*/
error = thread_link_mboxes(kg, ke);
if (error)
goto bad;
/*
* Set state and mailbox.
* From now on we are just a bound outgoing process.
* **Problem** userret is often called several times.
* it would be nice if this all happenned only on the first time
* through. (the scan for extra work etc.)
*/
td->td_flags &= ~TDF_UPCALLING;
#if 0
error = suword((caddr_t)ke->ke_mailbox +
offsetof(struct kse_mailbox, km_curthread), 0);
#else /* if user pointer arithmetic is ok in the kernel */
error = suword((caddr_t)&ke->ke_mailbox->km_curthread, 0);
#endif
if (!error)
return (0);
bad:
/*
* Things are going to be so screwed we should just kill the process.
* how do we do that?
*/
PROC_LOCK(td->td_proc);
psignal(td->td_proc, SIGSEGV);
PROC_UNLOCK(td->td_proc);
return (error); /* go sync */
}
/*
* Enforce single-threading.
*
* Returns 1 if the caller must abort (another thread is waiting to
* exit the process or similar). Process is locked!
* Returns 0 when you are successfully the only thread running.
* A process has successfully single threaded in the suspend mode when
* There are no threads in user mode. Threads in the kernel must be
* allowed to continue until they get to the user boundary. They may even
* copy out their return values and data before suspending. They may however be
* accellerated in reaching the user boundary as we will wake up
* any sleeping threads that are interruptable. (PCATCH).
*/
int
thread_single(int force_exit)
{
struct thread *td;
struct thread *td2;
struct proc *p;
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT((td != NULL), ("curthread is NULL"));
if ((p->p_flag & P_KSES) == 0)
return (0);
/* Is someone already single threading? */
if (p->p_singlethread)
return (1);
if (force_exit == SINGLE_EXIT)
p->p_flag |= P_SINGLE_EXIT;
else
p->p_flag &= ~P_SINGLE_EXIT;
p->p_flag |= P_STOPPED_SINGLE;
p->p_singlethread = td;
while ((p->p_numthreads - p->p_suspcount) != 1) {
mtx_lock_spin(&sched_lock);
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
if (TD_IS_INHIBITED(td2)) {
if (TD_IS_SUSPENDED(td2)) {
if (force_exit == SINGLE_EXIT) {
thread_unsuspend_one(td2);
}
}
if ( TD_IS_SLEEPING(td2)) {
if (td2->td_flags & TDF_CVWAITQ)
cv_waitq_remove(td2);
else
unsleep(td2);
break;
}
if (TD_CAN_RUN(td2))
setrunqueue(td2);
}
}
/*
* Wake us up when everyone else has suspended.
* In the mean time we suspend as well.
*/
thread_suspend_one(td);
mtx_unlock(&Giant);
PROC_UNLOCK(p);
mi_switch();
mtx_unlock_spin(&sched_lock);
mtx_lock(&Giant);
PROC_LOCK(p);
}
return (0);
}
/*
* Called in from locations that can safely check to see
* whether we have to suspend or at least throttle for a
* single-thread event (e.g. fork).
*
* Such locations include userret().
* If the "return_instead" argument is non zero, the thread must be able to
* accept 0 (caller may continue), or 1 (caller must abort) as a result.
*
* The 'return_instead' argument tells the function if it may do a
* thread_exit() or suspend, or whether the caller must abort and back
* out instead.
*
* If the thread that set the single_threading request has set the
* P_SINGLE_EXIT bit in the process flags then this call will never return
* if 'return_instead' is false, but will exit.
*
* P_SINGLE_EXIT | return_instead == 0| return_instead != 0
*---------------+--------------------+---------------------
* 0 | returns 0 | returns 0 or 1
* | when ST ends | immediatly
*---------------+--------------------+---------------------
* 1 | thread exits | returns 1
* | | immediatly
* 0 = thread_exit() or suspension ok,
* other = return error instead of stopping the thread.
*
* While a full suspension is under effect, even a single threading
* thread would be suspended if it made this call (but it shouldn't).
* This call should only be made from places where
* thread_exit() would be safe as that may be the outcome unless
* return_instead is set.
*/
int
thread_suspend_check(int return_instead)
{
struct thread *td;
struct proc *p;
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
while (P_SHOULDSTOP(p)) {
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
KASSERT(p->p_singlethread != NULL,
("singlethread not set"));
/*
* The only suspension in action is a
* single-threading. Single threader need not stop.
* XXX Should be safe to access unlocked
* as it can only be set to be true by us.
*/
if (p->p_singlethread == td)
return (0); /* Exempt from stopping. */
}
if (return_instead)
return (1);
/*
* If the process is waiting for us to exit,
* this thread should just suicide.
* Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
*/
if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
mtx_lock_spin(&sched_lock);
while (mtx_owned(&Giant))
mtx_unlock(&Giant);
thread_exit();
}
/*
* When a thread suspends, it just
* moves to the processes's suspend queue
* and stays there.
*
* XXXKSE if TDF_BOUND is true
* it will not release it's KSE which might
* lead to deadlock if there are not enough KSEs
* to complete all waiting threads.
* Maybe be able to 'lend' it out again.
* (lent kse's can not go back to userland?)
* and can only be lent in STOPPED state.
*/
mtx_lock_spin(&sched_lock);
if ((p->p_flag & P_STOPPED_SIG) &&
(p->p_suspcount+1 == p->p_numthreads)) {
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p->p_pptr);
if ((p->p_pptr->p_procsig->ps_flag &
PS_NOCLDSTOP) == 0) {
psignal(p->p_pptr, SIGCHLD);
}
PROC_UNLOCK(p->p_pptr);
mtx_lock_spin(&sched_lock);
}
mtx_assert(&Giant, MA_NOTOWNED);
thread_suspend_one(td);
PROC_UNLOCK(p);
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount) {
thread_unsuspend_one(p->p_singlethread);
}
}
p->p_stats->p_ru.ru_nivcsw++;
mi_switch();
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
}
return (0);
}
void
thread_suspend_one(struct thread *td)
{
struct proc *p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
p->p_suspcount++;
TD_SET_SUSPENDED(td);
TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq);
/*
* Hack: If we are suspending but are on the sleep queue
* then we are in msleep or the cv equivalent. We
* want to look like we have two Inhibitors.
*/
if (TD_ON_SLEEPQ(td))
TD_SET_SLEEPING(td);
}
void
thread_unsuspend_one(struct thread *td)
{
struct proc *p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
TAILQ_REMOVE(&p->p_suspended, td, td_runq);
TD_CLR_SUSPENDED(td);
p->p_suspcount--;
setrunnable(td);
}
/*
* Allow all threads blocked by single threading to continue running.
*/
void
thread_unsuspend(struct proc *p)
{
struct thread *td;
mtx_assert(&sched_lock, MA_OWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
if (!P_SHOULDSTOP(p)) {
while (( td = TAILQ_FIRST(&p->p_suspended))) {
thread_unsuspend_one(td);
}
} else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
(p->p_numthreads == p->p_suspcount)) {
/*
* Stopping everything also did the job for the single
* threading request. Now we've downgraded to single-threaded,
* let it continue.
*/
thread_unsuspend_one(p->p_singlethread);
}
}
void
thread_single_end(void)
{
struct thread *td;
struct proc *p;
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_flag &= ~P_STOPPED_SINGLE;
p->p_singlethread = NULL;
/*
* If there are other threads they mey now run,
* unless of course there is a blanket 'stop order'
* on the process. The single threader must be allowed
* to continue however as this is a bad place to stop.
*/
if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
mtx_lock_spin(&sched_lock);
while (( td = TAILQ_FIRST(&p->p_suspended))) {
thread_unsuspend_one(td);
}
mtx_unlock_spin(&sched_lock);
}
}