FreeBSD-5.3/sys/kern/kern_thread.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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/kern/kern_thread.c,v 1.193.2.8 2004/10/09 04:49:58 julian Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/sched.h>
#include <sys/sleepqueue.h>
#include <sys/turnstile.h>
#include <sys/ktr.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
/*
* KSEGRP related storage.
*/
static uma_zone_t ksegrp_zone;
static uma_zone_t thread_zone;
/* DEBUG ONLY */
SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
static int thread_debug = 0;
SYSCTL_INT(_kern_threads, OID_AUTO, debug, CTLFLAG_RW,
&thread_debug, 0, "thread debug");
int max_threads_per_proc = 1500;
SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
&max_threads_per_proc, 0, "Limit on threads per proc");
int max_groups_per_proc = 1500;
SYSCTL_INT(_kern_threads, OID_AUTO, max_groups_per_proc, CTLFLAG_RW,
&max_groups_per_proc, 0, "Limit on thread groups per proc");
int max_threads_hits;
SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD,
&max_threads_hits, 0, "");
int virtual_cpu;
#define RANGEOF(type, start, end) (offsetof(type, end) - offsetof(type, start))
TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
TAILQ_HEAD(, ksegrp) zombie_ksegrps = TAILQ_HEAD_INITIALIZER(zombie_ksegrps);
struct mtx kse_zombie_lock;
MTX_SYSINIT(kse_zombie_lock, &kse_zombie_lock, "kse zombie lock", MTX_SPIN);
static int
sysctl_kse_virtual_cpu(SYSCTL_HANDLER_ARGS)
{
int error, new_val;
int def_val;
def_val = mp_ncpus;
if (virtual_cpu == 0)
new_val = def_val;
else
new_val = virtual_cpu;
error = sysctl_handle_int(oidp, &new_val, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (new_val < 0)
return (EINVAL);
virtual_cpu = new_val;
return (0);
}
/* DEBUG ONLY */
SYSCTL_PROC(_kern_threads, OID_AUTO, virtual_cpu, CTLTYPE_INT|CTLFLAG_RW,
0, sizeof(virtual_cpu), sysctl_kse_virtual_cpu, "I",
"debug virtual cpus");
/*
* Thread ID allocator. The allocator keeps track of assigned IDs by
* using a bitmap. The bitmap is created in parts. The parts are linked
* together.
*/
typedef u_long tid_bitmap_word;
#define TID_IDS_PER_PART 1024
#define TID_IDS_PER_IDX (sizeof(tid_bitmap_word) << 3)
#define TID_BITMAP_SIZE (TID_IDS_PER_PART / TID_IDS_PER_IDX)
#define TID_MIN (PID_MAX + 1)
struct tid_bitmap_part {
STAILQ_ENTRY(tid_bitmap_part) bmp_next;
tid_bitmap_word bmp_bitmap[TID_BITMAP_SIZE];
lwpid_t bmp_base;
int bmp_free;
};
static STAILQ_HEAD(, tid_bitmap_part) tid_bitmap =
STAILQ_HEAD_INITIALIZER(tid_bitmap);
static uma_zone_t tid_zone;
struct mtx tid_lock;
MTX_SYSINIT(tid_lock, &tid_lock, "TID lock", MTX_DEF);
/*
* Prepare a thread for use.
*/
static int
thread_ctor(void *mem, int size, void *arg, int flags)
{
struct thread *td;
td = (struct thread *)mem;
td->td_state = TDS_INACTIVE;
td->td_oncpu = NOCPU;
/*
* Note that td_critnest begins life as 1 because the thread is not
* running and is thereby implicitly waiting to be on the receiving
* end of a context switch. A context switch must occur inside a
* critical section, and in fact, includes hand-off of the sched_lock.
* After a context switch to a newly created thread, it will release
* sched_lock for the first time, and its td_critnest will hit 0 for
* the first time. This happens on the far end of a context switch,
* and when it context switches away from itself, it will in fact go
* back into a critical section, and hand off the sched lock to the
* next thread.
*/
td->td_critnest = 1;
return (0);
}
/*
* Reclaim a thread after use.
*/
static void
thread_dtor(void *mem, int size, void *arg)
{
struct thread *td;
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
sched_newthread(td);
}
/*
* Initialize type-stable parts of a thread (when newly created).
*/
static int
thread_init(void *mem, int size, int flags)
{
struct thread *td;
struct tid_bitmap_part *bmp, *new;
int bit, idx;
td = (struct thread *)mem;
mtx_lock(&tid_lock);
STAILQ_FOREACH(bmp, &tid_bitmap, bmp_next) {
if (bmp->bmp_free)
break;
}
/* Create a new bitmap if we run out of free bits. */
if (bmp == NULL) {
mtx_unlock(&tid_lock);
new = uma_zalloc(tid_zone, M_WAITOK);
mtx_lock(&tid_lock);
bmp = STAILQ_LAST(&tid_bitmap, tid_bitmap_part, bmp_next);
if (bmp == NULL || bmp->bmp_free < TID_IDS_PER_PART/2) {
/* 1=free, 0=assigned. This way we can use ffsl(). */
memset(new->bmp_bitmap, ~0U, sizeof(new->bmp_bitmap));
new->bmp_base = (bmp == NULL) ? TID_MIN :
bmp->bmp_base + TID_IDS_PER_PART;
new->bmp_free = TID_IDS_PER_PART;
STAILQ_INSERT_TAIL(&tid_bitmap, new, bmp_next);
bmp = new;
new = NULL;
}
} else
new = NULL;
/* We have a bitmap with available IDs. */
idx = 0;
while (idx < TID_BITMAP_SIZE && bmp->bmp_bitmap[idx] == 0UL)
idx++;
bit = ffsl(bmp->bmp_bitmap[idx]) - 1;
td->td_tid = bmp->bmp_base + idx * TID_IDS_PER_IDX + bit;
bmp->bmp_bitmap[idx] &= ~(1UL << bit);
bmp->bmp_free--;
mtx_unlock(&tid_lock);
if (new != NULL)
uma_zfree(tid_zone, new);
vm_thread_new(td, 0);
cpu_thread_setup(td);
td->td_sleepqueue = sleepq_alloc();
td->td_turnstile = turnstile_alloc();
td->td_sched = (struct td_sched *)&td[1];
sched_newthread(td);
return (0);
}
/*
* Tear down type-stable parts of a thread (just before being discarded).
*/
static void
thread_fini(void *mem, int size)
{
struct thread *td;
struct tid_bitmap_part *bmp;
lwpid_t tid;
int bit, idx;
td = (struct thread *)mem;
turnstile_free(td->td_turnstile);
sleepq_free(td->td_sleepqueue);
vm_thread_dispose(td);
STAILQ_FOREACH(bmp, &tid_bitmap, bmp_next) {
if (td->td_tid >= bmp->bmp_base &&
td->td_tid < bmp->bmp_base + TID_IDS_PER_PART)
break;
}
KASSERT(bmp != NULL, ("No TID bitmap?"));
mtx_lock(&tid_lock);
tid = td->td_tid - bmp->bmp_base;
idx = tid / TID_IDS_PER_IDX;
bit = 1UL << (tid % TID_IDS_PER_IDX);
bmp->bmp_bitmap[idx] |= bit;
bmp->bmp_free++;
mtx_unlock(&tid_lock);
}
/*
* Initialize type-stable parts of a ksegrp (when newly created).
*/
static int
ksegrp_ctor(void *mem, int size, void *arg, int flags)
{
struct ksegrp *kg;
kg = (struct ksegrp *)mem;
bzero(mem, size);
kg->kg_sched = (struct kg_sched *)&kg[1];
return (0);
}
void
ksegrp_link(struct ksegrp *kg, struct proc *p)
{
TAILQ_INIT(&kg->kg_threads);
TAILQ_INIT(&kg->kg_runq); /* links with td_runq */
TAILQ_INIT(&kg->kg_slpq); /* links with td_runq */
TAILQ_INIT(&kg->kg_upcalls); /* all upcall structure in ksegrp */
kg->kg_proc = p;
/*
* the following counters are in the -zero- section
* and may not need clearing
*/
kg->kg_numthreads = 0;
kg->kg_runnable = 0;
kg->kg_numupcalls = 0;
/* link it in now that it's consistent */
p->p_numksegrps++;
TAILQ_INSERT_HEAD(&p->p_ksegrps, kg, kg_ksegrp);
}
/*
* Called from:
* thread-exit()
*/
void
ksegrp_unlink(struct ksegrp *kg)
{
struct proc *p;
mtx_assert(&sched_lock, MA_OWNED);
KASSERT((kg->kg_numthreads == 0), ("ksegrp_unlink: residual threads"));
KASSERT((kg->kg_numupcalls == 0), ("ksegrp_unlink: residual upcalls"));
p = kg->kg_proc;
TAILQ_REMOVE(&p->p_ksegrps, kg, kg_ksegrp);
p->p_numksegrps--;
/*
* Aggregate stats from the KSE
*/
}
/*
* For a newly created process,
* link up all the structures and its initial threads etc.
* called from:
* {arch}/{arch}/machdep.c ia64_init(), init386() etc.
* proc_dtor() (should go away)
* proc_init()
*/
void
proc_linkup(struct proc *p, struct ksegrp *kg, struct thread *td)
{
TAILQ_INIT(&p->p_ksegrps); /* all ksegrps in proc */
TAILQ_INIT(&p->p_threads); /* all threads in proc */
TAILQ_INIT(&p->p_suspended); /* Threads suspended */
p->p_numksegrps = 0;
p->p_numthreads = 0;
ksegrp_link(kg, p);
thread_link(td, kg);
}
/*
* Initialize global thread allocation resources.
*/
void
threadinit(void)
{
thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
thread_ctor, thread_dtor, thread_init, thread_fini,
UMA_ALIGN_CACHE, 0);
tid_zone = uma_zcreate("TID", sizeof(struct tid_bitmap_part),
NULL, NULL, NULL, NULL, UMA_ALIGN_CACHE, 0);
ksegrp_zone = uma_zcreate("KSEGRP", sched_sizeof_ksegrp(),
ksegrp_ctor, NULL, NULL, NULL,
UMA_ALIGN_CACHE, 0);
kseinit(); /* set up kse specific stuff e.g. upcall zone*/
}
/*
* Stash an embarasingly extra thread into the zombie thread queue.
*/
void
thread_stash(struct thread *td)
{
mtx_lock_spin(&kse_zombie_lock);
TAILQ_INSERT_HEAD(&zombie_threads, td, td_runq);
mtx_unlock_spin(&kse_zombie_lock);
}
/*
* Stash an embarasingly extra ksegrp into the zombie ksegrp queue.
*/
void
ksegrp_stash(struct ksegrp *kg)
{
mtx_lock_spin(&kse_zombie_lock);
TAILQ_INSERT_HEAD(&zombie_ksegrps, kg, kg_ksegrp);
mtx_unlock_spin(&kse_zombie_lock);
}
/*
* Reap zombie kse resource.
*/
void
thread_reap(void)
{
struct thread *td_first, *td_next;
struct ksegrp *kg_first, * kg_next;
/*
* 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))
|| (!TAILQ_EMPTY(&zombie_ksegrps))) {
mtx_lock_spin(&kse_zombie_lock);
td_first = TAILQ_FIRST(&zombie_threads);
kg_first = TAILQ_FIRST(&zombie_ksegrps);
if (td_first)
TAILQ_INIT(&zombie_threads);
if (kg_first)
TAILQ_INIT(&zombie_ksegrps);
mtx_unlock_spin(&kse_zombie_lock);
while (td_first) {
td_next = TAILQ_NEXT(td_first, td_runq);
if (td_first->td_ucred)
crfree(td_first->td_ucred);
thread_free(td_first);
td_first = td_next;
}
while (kg_first) {
kg_next = TAILQ_NEXT(kg_first, kg_ksegrp);
ksegrp_free(kg_first);
kg_first = kg_next;
}
/*
* there will always be a thread on the list if one of these
* is there.
*/
kse_GC();
}
}
/*
* Allocate a ksegrp.
*/
struct ksegrp *
ksegrp_alloc(void)
{
return (uma_zalloc(ksegrp_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 thread.
*/
void
thread_free(struct thread *td)
{
cpu_thread_clean(td);
uma_zfree(thread_zone, td);
}
/*
* Discard the current thread and exit from its context.
* Always called with scheduler locked.
*
* Because we can't free a thread while we're operating under its context,
* push the current thread into our CPU's deadthread holder. This means
* we needn't worry about someone else grabbing our context before we
* do a cpu_throw(). This may not be needed now as we are under schedlock.
* Maybe we can just do a thread_stash() as thr_exit1 does.
*/
/* XXX
* libthr expects its thread exit to return for the last
* thread, meaning that the program is back to non-threaded
* mode I guess. Because we do this (cpu_throw) unconditionally
* here, they have their own version of it. (thr_exit1())
* that doesn't do it all if this was the last thread.
* It is also called from thread_suspend_check().
* Of course in the end, they end up coming here through exit1
* anyhow.. After fixing 'thr' to play by the rules we should be able
* to merge these two functions together.
*
* called from:
* exit1()
* kse_exit()
* thr_exit()
* thread_user_enter()
* thread_userret()
* thread_suspend_check()
*/
void
thread_exit(void)
{
struct thread *td;
struct proc *p;
struct ksegrp *kg;
td = curthread;
kg = td->td_ksegrp;
p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT(p != NULL, ("thread exiting without a process"));
KASSERT(kg != NULL, ("thread exiting without a kse group"));
CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
(long)p->p_pid, p->p_comm);
if (td->td_standin != NULL) {
/*
* Note that we don't need to free the cred here as it
* is done in thread_reap().
*/
thread_stash(td->td_standin);
td->td_standin = NULL;
}
/*
* drop FPU & debug register state storage, or any other
* architecture specific resources that
* would not be on a new untouched process.
*/
cpu_thread_exit(td); /* XXXSMP */
/*
* The thread is exiting. scheduler can release its stuff
* and collect stats etc.
*/
sched_thread_exit(td);
/*
* The last thread is left attached to the process
* So that the whole bundle gets recycled. Skip
* all this stuff if we never had threads.
* EXIT clears all sign of other threads when
* it goes to single threading, so the last thread always
* takes the short path.
*/
if (p->p_flag & P_HADTHREADS) {
if (p->p_numthreads > 1) {
thread_unlink(td);
/* XXX first arg not used in 4BSD or ULE */
sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
/*
* as we are exiting there is room for another
* to be created.
*/
if (p->p_maxthrwaits)
wakeup(&p->p_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);
}
}
/*
* Because each upcall structure has an owner thread,
* owner thread exits only when process is in exiting
* state, so upcall to userland is no longer needed,
* deleting upcall structure is safe here.
* So when all threads in a group is exited, all upcalls
* in the group should be automatically freed.
* XXXKSE This is a KSE thing and should be exported
* there somehow.
*/
upcall_remove(td);
/*
* If the thread we unlinked above was the last one,
* then this ksegrp should go away too.
*/
if (kg->kg_numthreads == 0) {
/*
* let the scheduler know about this in case
* it needs to recover stats or resources.
* Theoretically we could let
* sched_exit_ksegrp() do the equivalent of
* setting the concurrency to 0
* but don't do it yet to avoid changing
* the existing scheduler code until we
* are ready.
* We supply a random other ksegrp
* as the recipient of any built up
* cpu usage etc. (If the scheduler wants it).
* XXXKSE
* This is probably not fair so think of
* a better answer.
*/
sched_exit_ksegrp(FIRST_KSEGRP_IN_PROC(p), td);
sched_set_concurrency(kg, 0); /* XXX TEMP */
ksegrp_unlink(kg);
ksegrp_stash(kg);
}
PROC_UNLOCK(p);
td->td_ksegrp = NULL;
PCPU_SET(deadthread, td);
} else {
/*
* The last thread is exiting.. but not through exit()
* what should we do?
* Theoretically this can't happen
* exit1() - clears threading flags before coming here
* kse_exit() - treats last thread specially
* thr_exit() - treats last thread specially
* thread_user_enter() - only if more exist
* thread_userret() - only if more exist
* thread_suspend_check() - only if more exist
*/
panic ("thread_exit: Last thread exiting on its own");
}
} else {
/*
* non threaded process comes here.
* This includes an EX threaded process that is coming
* here via exit1(). (exit1 dethreads the proc first).
*/
PROC_UNLOCK(p);
}
td->td_state = TDS_INACTIVE;
CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
cpu_throw(td, choosethread());
panic("I'm a teapot!");
/* NOTREACHED */
}
/*
* Do any thread specific cleanups that may be needed in wait()
* called with Giant, proc and schedlock not held.
*/
void
thread_wait(struct proc *p)
{
struct thread *td;
mtx_assert(&Giant, MA_NOTOWNED);
KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
KASSERT((p->p_numksegrps == 1), ("Multiple ksegrps in wait1()"));
FOREACH_THREAD_IN_PROC(p, td) {
if (td->td_standin != NULL) {
crfree(td->td_ucred);
td->td_ucred = NULL;
thread_free(td->td_standin);
td->td_standin = NULL;
}
cpu_thread_clean(td);
crfree(td->td_ucred);
}
thread_reap(); /* check for zombie threads etc. */
}
/*
* 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.
* Called from:
* proc_linkup()
* thread_schedule_upcall()
* thr_create()
*/
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_flags = 0;
td->td_kflags = 0;
LIST_INIT(&td->td_contested);
callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
TAILQ_INSERT_HEAD(&kg->kg_threads, td, td_kglist);
p->p_numthreads++;
kg->kg_numthreads++;
}
/*
* Convert a process with one thread to an unthreaded process.
* Called from:
* thread_single(exit) (called from execve and exit)
* kse_exit() XXX may need cleaning up wrt KSE stuff
*/
void
thread_unthread(struct thread *td)
{
struct proc *p = td->td_proc;
KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
upcall_remove(td);
p->p_flag &= ~(P_SA|P_HADTHREADS);
td->td_mailbox = NULL;
td->td_pflags &= ~(TDP_SA | TDP_CAN_UNBIND);
if (td->td_standin != NULL) {
thread_stash(td->td_standin);
td->td_standin = NULL;
}
sched_set_concurrency(td->td_ksegrp, 1);
}
/*
* Called from:
* thread_exit()
*/
void
thread_unlink(struct thread *td)
{
struct proc *p = td->td_proc;
struct ksegrp *kg = td->td_ksegrp;
mtx_assert(&sched_lock, MA_OWNED);
TAILQ_REMOVE(&p->p_threads, td, td_plist);
p->p_numthreads--;
TAILQ_REMOVE(&kg->kg_threads, td, td_kglist);
kg->kg_numthreads--;
/* could clear a few other things here */
/* Must NOT clear links to proc and ksegrp! */
}
/*
* 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 mode)
{
struct thread *td;
struct thread *td2;
struct proc *p;
int remaining;
td = curthread;
p = td->td_proc;
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT((td != NULL), ("curthread is NULL"));
if ((p->p_flag & P_HADTHREADS) == 0)
return (0);
/* Is someone already single threading? */
if (p->p_singlethread != NULL && p->p_singlethread != td)
return (1);
if (mode == SINGLE_EXIT) {
p->p_flag |= P_SINGLE_EXIT;
p->p_flag &= ~P_SINGLE_BOUNDARY;
} else {
p->p_flag &= ~P_SINGLE_EXIT;
if (mode == SINGLE_BOUNDARY)
p->p_flag |= P_SINGLE_BOUNDARY;
else
p->p_flag &= ~P_SINGLE_BOUNDARY;
}
p->p_flag |= P_STOPPED_SINGLE;
mtx_lock_spin(&sched_lock);
p->p_singlethread = td;
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
while (remaining != 1) {
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
td2->td_flags |= TDF_ASTPENDING;
if (TD_IS_INHIBITED(td2)) {
switch (mode) {
case SINGLE_EXIT:
if (td->td_flags & TDF_DBSUSPEND)
td->td_flags &= ~TDF_DBSUSPEND;
if (TD_IS_SUSPENDED(td2))
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
sleepq_abort(td2);
break;
case SINGLE_BOUNDARY:
if (TD_IS_SUSPENDED(td2) &&
!(td2->td_flags & TDF_BOUNDARY))
thread_unsuspend_one(td2);
if (TD_ON_SLEEPQ(td2) &&
(td2->td_flags & TDF_SINTR))
sleepq_abort(td2);
break;
default:
if (TD_IS_SUSPENDED(td2))
continue;
/*
* maybe other inhibitted states too?
* XXXKSE Is it totally safe to
* suspend a non-interruptable thread?
*/
if (td2->td_inhibitors &
(TDI_SLEEPING | TDI_SWAPPED))
thread_suspend_one(td2);
break;
}
}
}
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
/*
* Maybe we suspended some threads.. was it enough?
*/
if (remaining == 1)
break;
/*
* Wake us up when everyone else has suspended.
* In the mean time we suspend as well.
*/
thread_suspend_one(td);
PROC_UNLOCK(p);
mi_switch(SW_VOL, NULL);
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
mtx_lock_spin(&sched_lock);
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else
remaining = p->p_numthreads - p->p_suspcount;
}
if (mode == SINGLE_EXIT) {
/*
* We have gotten rid of all the other threads and we
* are about to either exit or exec. In either case,
* we try our utmost to revert to being a non-threaded
* process.
*/
p->p_singlethread = NULL;
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
thread_unthread(td);
}
mtx_unlock_spin(&sched_lock);
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;
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
while (P_SHOULDSTOP(p) ||
((p->p_flag & P_TRACED) && (td->td_flags & TDF_DBSUSPEND))) {
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 ((p->p_flag & P_SINGLE_EXIT) && return_instead)
return (1);
/* Should we goto user boundary if we didn't come from there? */
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
(p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
return (1);
mtx_lock_spin(&sched_lock);
thread_stopped(p);
/*
* 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))
thread_exit();
/*
* When a thread suspends, it just
* moves to the processes's suspend queue
* and stays there.
*/
thread_suspend_one(td);
if (return_instead == 0) {
p->p_boundary_count++;
td->td_flags |= TDF_BOUNDARY;
}
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount)
thread_unsuspend_one(p->p_singlethread);
}
PROC_UNLOCK(p);
mi_switch(SW_INVOL, NULL);
if (return_instead == 0) {
p->p_boundary_count--;
td->td_flags &= ~TDF_BOUNDARY;
}
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);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
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.
* May already be set.. doesn't matter.
*/
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);
PROC_LOCK_ASSERT(p, 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);
}
}
/*
* End the single threading mode..
*/
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_SINGLE_EXIT | P_SINGLE_BOUNDARY);
mtx_lock_spin(&sched_lock);
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))) {
while (( td = TAILQ_FIRST(&p->p_suspended))) {
thread_unsuspend_one(td);
}
}
mtx_unlock_spin(&sched_lock);
}
/*
* Called before going into an interruptible sleep to see if we have been
* interrupted or requested to exit.
*/
int
thread_sleep_check(struct thread *td)
{
struct proc *p;
p = td->td_proc;
mtx_assert(&sched_lock, MA_OWNED);
if (p->p_flag & P_HADTHREADS) {
if (p->p_singlethread != td) {
if (p->p_flag & P_SINGLE_EXIT)
return (EINTR);
if (p->p_flag & P_SINGLE_BOUNDARY)
return (ERESTART);
}
if (td->td_flags & TDF_INTERRUPT)
return (td->td_intrval);
}
return (0);
}