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freebsd/sys/kern/kern_thread.c
Konstantin Belousov 1b253694f4 Mark struct thread zone as type-stable. 
When establishing the locking state for several lock types (including
blockable mutexes and sx) failed, locking primitives try to spin while
the owner thread is running.  The spinning loop performs the test for
running condition by dereferencing the owner->td_state field of the
owner thread.  If the owner thread exited while spinner was put off
the processor, it is harmless to access reused struct thread owner,
since in some near future the current processor would notice the owner
change and make appropriate progress.  But it could be that the page
which carried the freed struct thread was unmapped, then we fault
(this cannot happen on amd64).

For now, disallowing free of the struct thread seems to be good
enough, and tests which create a lot of threads once, did not
demonstrated regressions.

Reviewed by:	jhb, pho
Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D3908
2015-10-20 20:29:21 +00:00

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/*-
* 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 "opt_witness.h"
#include "opt_hwpmc_hooks.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#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/rangelock.h>
#include <sys/resourcevar.h>
#include <sys/sdt.h>
#include <sys/smp.h>
#include <sys/sched.h>
#include <sys/sleepqueue.h>
#include <sys/selinfo.h>
#include <sys/sysent.h>
#include <sys/turnstile.h>
#include <sys/ktr.h>
#include <sys/rwlock.h>
#include <sys/umtx.h>
#include <sys/cpuset.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <security/audit/audit.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <vm/vm_domain.h>
#include <sys/eventhandler.h>
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, , , lwp__exit);
/*
* thread related storage.
*/
static uma_zone_t thread_zone;
TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
static struct mtx zombie_lock;
MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
static void thread_zombie(struct thread *);
static int thread_unsuspend_one(struct thread *td, struct proc *p,
bool boundary);
#define TID_BUFFER_SIZE 1024
struct mtx tid_lock;
static struct unrhdr *tid_unrhdr;
static lwpid_t tid_buffer[TID_BUFFER_SIZE];
static int tid_head, tid_tail;
static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
struct tidhashhead *tidhashtbl;
u_long tidhash;
struct rwlock tidhash_lock;
static lwpid_t
tid_alloc(void)
{
lwpid_t tid;
tid = alloc_unr(tid_unrhdr);
if (tid != -1)
return (tid);
mtx_lock(&tid_lock);
if (tid_head == tid_tail) {
mtx_unlock(&tid_lock);
return (-1);
}
tid = tid_buffer[tid_head];
tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
mtx_unlock(&tid_lock);
return (tid);
}
static void
tid_free(lwpid_t tid)
{
lwpid_t tmp_tid = -1;
mtx_lock(&tid_lock);
if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
tmp_tid = tid_buffer[tid_head];
tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
}
tid_buffer[tid_tail] = tid;
tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE;
mtx_unlock(&tid_lock);
if (tmp_tid != -1)
free_unr(tid_unrhdr, tmp_tid);
}
/*
* 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;
td->td_tid = tid_alloc();
/*
* 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.
*/
td->td_critnest = 1;
td->td_lend_user_pri = PRI_MAX;
EVENTHANDLER_INVOKE(thread_ctor, td);
#ifdef AUDIT
audit_thread_alloc(td);
#endif
umtx_thread_alloc(td);
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
#ifdef AUDIT
audit_thread_free(td);
#endif
/* Free all OSD associated to this thread. */
osd_thread_exit(td);
EVENTHANDLER_INVOKE(thread_dtor, td);
tid_free(td->td_tid);
}
/*
* Initialize type-stable parts of a thread (when newly created).
*/
static int
thread_init(void *mem, int size, int flags)
{
struct thread *td;
td = (struct thread *)mem;
td->td_sleepqueue = sleepq_alloc();
td->td_turnstile = turnstile_alloc();
td->td_rlqe = NULL;
EVENTHANDLER_INVOKE(thread_init, td);
td->td_sched = (struct td_sched *)&td[1];
umtx_thread_init(td);
td->td_kstack = 0;
td->td_sel = NULL;
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;
td = (struct thread *)mem;
EVENTHANDLER_INVOKE(thread_fini, td);
rlqentry_free(td->td_rlqe);
turnstile_free(td->td_turnstile);
sleepq_free(td->td_sleepqueue);
umtx_thread_fini(td);
seltdfini(td);
}
/*
* For a newly created process,
* link up all the structures and its initial threads etc.
* called from:
* {arch}/{arch}/machdep.c {arch}_init(), init386() etc.
* proc_dtor() (should go away)
* proc_init()
*/
void
proc_linkup0(struct proc *p, struct thread *td)
{
TAILQ_INIT(&p->p_threads); /* all threads in proc */
proc_linkup(p, td);
}
void
proc_linkup(struct proc *p, struct thread *td)
{
sigqueue_init(&p->p_sigqueue, p);
p->p_ksi = ksiginfo_alloc(1);
if (p->p_ksi != NULL) {
/* XXX p_ksi may be null if ksiginfo zone is not ready */
p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
}
LIST_INIT(&p->p_mqnotifier);
p->p_numthreads = 0;
thread_link(td, p);
}
/*
* Initialize global thread allocation resources.
*/
void
threadinit(void)
{
mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
/*
* pid_max cannot be greater than PID_MAX.
* leave one number for thread0.
*/
tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
thread_ctor, thread_dtor, thread_init, thread_fini,
16 - 1, UMA_ZONE_NOFREE);
tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
rw_init(&tidhash_lock, "tidhash");
}
/*
* Place an unused thread on the zombie list.
* Use the slpq as that must be unused by now.
*/
void
thread_zombie(struct thread *td)
{
mtx_lock_spin(&zombie_lock);
TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
mtx_unlock_spin(&zombie_lock);
}
/*
* Release a thread that has exited after cpu_throw().
*/
void
thread_stash(struct thread *td)
{
atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
thread_zombie(td);
}
/*
* Reap zombie resources.
*/
void
thread_reap(void)
{
struct thread *td_first, *td_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)) {
mtx_lock_spin(&zombie_lock);
td_first = TAILQ_FIRST(&zombie_threads);
if (td_first)
TAILQ_INIT(&zombie_threads);
mtx_unlock_spin(&zombie_lock);
while (td_first) {
td_next = TAILQ_NEXT(td_first, td_slpq);
thread_cow_free(td_first);
thread_free(td_first);
td_first = td_next;
}
}
}
/*
* Allocate a thread.
*/
struct thread *
thread_alloc(int pages)
{
struct thread *td;
thread_reap(); /* check if any zombies to get */
td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
if (!vm_thread_new(td, pages)) {
uma_zfree(thread_zone, td);
return (NULL);
}
cpu_thread_alloc(td);
vm_domain_policy_init(&td->td_vm_dom_policy);
return (td);
}
int
thread_alloc_stack(struct thread *td, int pages)
{
KASSERT(td->td_kstack == 0,
("thread_alloc_stack called on a thread with kstack"));
if (!vm_thread_new(td, pages))
return (0);
cpu_thread_alloc(td);
return (1);
}
/*
* Deallocate a thread.
*/
void
thread_free(struct thread *td)
{
lock_profile_thread_exit(td);
if (td->td_cpuset)
cpuset_rel(td->td_cpuset);
td->td_cpuset = NULL;
cpu_thread_free(td);
if (td->td_kstack != 0)
vm_thread_dispose(td);
vm_domain_policy_cleanup(&td->td_vm_dom_policy);
uma_zfree(thread_zone, td);
}
void
thread_cow_get_proc(struct thread *newtd, struct proc *p)
{
PROC_LOCK_ASSERT(p, MA_OWNED);
newtd->td_ucred = crhold(p->p_ucred);
newtd->td_limit = lim_hold(p->p_limit);
newtd->td_cowgen = p->p_cowgen;
}
void
thread_cow_get(struct thread *newtd, struct thread *td)
{
newtd->td_ucred = crhold(td->td_ucred);
newtd->td_limit = lim_hold(td->td_limit);
newtd->td_cowgen = td->td_cowgen;
}
void
thread_cow_free(struct thread *td)
{
if (td->td_ucred != NULL)
crfree(td->td_ucred);
if (td->td_limit != NULL)
lim_free(td->td_limit);
}
void
thread_cow_update(struct thread *td)
{
struct proc *p;
struct ucred *oldcred;
struct plimit *oldlimit;
p = td->td_proc;
oldcred = NULL;
oldlimit = NULL;
PROC_LOCK(p);
if (td->td_ucred != p->p_ucred) {
oldcred = td->td_ucred;
td->td_ucred = crhold(p->p_ucred);
}
if (td->td_limit != p->p_limit) {
oldlimit = td->td_limit;
td->td_limit = lim_hold(p->p_limit);
}
td->td_cowgen = p->p_cowgen;
PROC_UNLOCK(p);
if (oldcred != NULL)
crfree(oldcred);
if (oldlimit != NULL)
lim_free(oldlimit);
}
/*
* 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().
*/
void
thread_exit(void)
{
uint64_t runtime, new_switchtime;
struct thread *td;
struct thread *td2;
struct proc *p;
int wakeup_swapper;
td = curthread;
p = td->td_proc;
PROC_SLOCK_ASSERT(p, MA_OWNED);
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT(p != NULL, ("thread exiting without a process"));
CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
(long)p->p_pid, td->td_name);
KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
#ifdef AUDIT
AUDIT_SYSCALL_EXIT(0, td);
#endif
/*
* 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 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) {
atomic_add_int(&td->td_proc->p_exitthreads, 1);
thread_unlink(td);
td2 = FIRST_THREAD_IN_PROC(p);
sched_exit_thread(td2, td);
/*
* The test below is NOT true if we are the
* sole exiting thread. P_STOPPED_SINGLE 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_lock(p->p_singlethread);
wakeup_swapper = thread_unsuspend_one(
p->p_singlethread, p, false);
thread_unlock(p->p_singlethread);
if (wakeup_swapper)
kick_proc0();
}
}
PCPU_SET(deadthread, td);
} else {
/*
* The last thread is exiting.. but not through exit()
*/
panic ("thread_exit: Last thread exiting on its own");
}
}
#ifdef HWPMC_HOOKS
/*
* If this thread is part of a process that is being tracked by hwpmc(4),
* inform the module of the thread's impending exit.
*/
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
#endif
PROC_UNLOCK(p);
PROC_STATLOCK(p);
thread_lock(td);
PROC_SUNLOCK(p);
/* Do the same timestamp bookkeeping that mi_switch() would do. */
new_switchtime = cpu_ticks();
runtime = new_switchtime - PCPU_GET(switchtime);
td->td_runtime += runtime;
td->td_incruntime += runtime;
PCPU_SET(switchtime, new_switchtime);
PCPU_SET(switchticks, ticks);
PCPU_INC(cnt.v_swtch);
/* Save our resource usage in our process. */
td->td_ru.ru_nvcsw++;
ruxagg(p, td);
rucollect(&p->p_ru, &td->td_ru);
PROC_STATUNLOCK(p);
td->td_state = TDS_INACTIVE;
#ifdef WITNESS
witness_thread_exit(td);
#endif
CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
sched_throw(td);
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 thread_wait()"));
KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
td = FIRST_THREAD_IN_PROC(p);
/* Lock the last thread so we spin until it exits cpu_throw(). */
thread_lock(td);
thread_unlock(td);
lock_profile_thread_exit(td);
cpuset_rel(td->td_cpuset);
td->td_cpuset = NULL;
cpu_thread_clean(td);
thread_cow_free(td);
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.
*/
void
thread_link(struct thread *td, struct proc *p)
{
/*
* XXX This can't be enabled because it's called for proc0 before
* its lock has been created.
* PROC_LOCK_ASSERT(p, MA_OWNED);
*/
td->td_state = TDS_INACTIVE;
td->td_proc = p;
td->td_flags = TDF_INMEM;
LIST_INIT(&td->td_contested);
LIST_INIT(&td->td_lprof[0]);
LIST_INIT(&td->td_lprof[1]);
sigqueue_init(&td->td_sigqueue, p);
callout_init(&td->td_slpcallout, 1);
TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
p->p_numthreads++;
}
/*
* Called from:
* thread_exit()
*/
void
thread_unlink(struct thread *td)
{
struct proc *p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
TAILQ_REMOVE(&p->p_threads, td, td_plist);
p->p_numthreads--;
/* could clear a few other things here */
/* Must NOT clear links to proc! */
}
static int
calc_remaining(struct proc *p, int mode)
{
int remaining;
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
if (mode == SINGLE_EXIT)
remaining = p->p_numthreads;
else if (mode == SINGLE_BOUNDARY)
remaining = p->p_numthreads - p->p_boundary_count;
else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
remaining = p->p_numthreads - p->p_suspcount;
else
panic("calc_remaining: wrong mode %d", mode);
return (remaining);
}
static int
remain_for_mode(int mode)
{
return (mode == SINGLE_ALLPROC ? 0 : 1);
}
static int
weed_inhib(int mode, struct thread *td2, struct proc *p)
{
int wakeup_swapper;
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
THREAD_LOCK_ASSERT(td2, MA_OWNED);
wakeup_swapper = 0;
switch (mode) {
case SINGLE_EXIT:
if (TD_IS_SUSPENDED(td2))
wakeup_swapper |= thread_unsuspend_one(td2, p, true);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, EINTR);
break;
case SINGLE_BOUNDARY:
if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
wakeup_swapper |= thread_unsuspend_one(td2, p, false);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, ERESTART);
break;
case SINGLE_NO_EXIT:
if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
wakeup_swapper |= thread_unsuspend_one(td2, p, false);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
wakeup_swapper |= sleepq_abort(td2, ERESTART);
break;
case SINGLE_ALLPROC:
/*
* ALLPROC suspend tries to avoid spurious EINTR for
* threads sleeping interruptable, by suspending the
* thread directly, similarly to sig_suspend_threads().
* Since such sleep is not performed at the user
* boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP
* is used to avoid immediate un-suspend.
*/
if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY |
TDF_ALLPROCSUSP)) == 0)
wakeup_swapper |= thread_unsuspend_one(td2, p, false);
if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) {
if ((td2->td_flags & TDF_SBDRY) == 0) {
thread_suspend_one(td2);
td2->td_flags |= TDF_ALLPROCSUSP;
} else {
wakeup_swapper |= sleepq_abort(td2, ERESTART);
}
}
break;
}
return (wakeup_swapper);
}
/*
* 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
* accelerated in reaching the user boundary as we will wake up
* any sleeping threads that are interruptable. (PCATCH).
*/
int
thread_single(struct proc *p, int mode)
{
struct thread *td;
struct thread *td2;
int remaining, wakeup_swapper;
td = curthread;
KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
("invalid mode %d", mode));
/*
* If allowing non-ALLPROC singlethreading for non-curproc
* callers, calc_remaining() and remain_for_mode() should be
* adjusted to also account for td->td_proc != p. For now
* this is not implemented because it is not used.
*/
KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
(mode != SINGLE_ALLPROC && td->td_proc == p),
("mode %d proc %p curproc %p", mode, p, td->td_proc));
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC)
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;
}
if (mode == SINGLE_ALLPROC)
p->p_flag |= P_TOTAL_STOP;
p->p_flag |= P_STOPPED_SINGLE;
PROC_SLOCK(p);
p->p_singlethread = td;
remaining = calc_remaining(p, mode);
while (remaining != remain_for_mode(mode)) {
if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
goto stopme;
wakeup_swapper = 0;
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
thread_lock(td2);
td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
if (TD_IS_INHIBITED(td2)) {
wakeup_swapper |= weed_inhib(mode, td2, p);
#ifdef SMP
} else if (TD_IS_RUNNING(td2) && td != td2) {
forward_signal(td2);
#endif
}
thread_unlock(td2);
}
if (wakeup_swapper)
kick_proc0();
remaining = calc_remaining(p, mode);
/*
* Maybe we suspended some threads.. was it enough?
*/
if (remaining == remain_for_mode(mode))
break;
stopme:
/*
* Wake us up when everyone else has suspended.
* In the mean time we suspend as well.
*/
thread_suspend_switch(td, p);
remaining = calc_remaining(p, mode);
}
if (mode == SINGLE_EXIT) {
/*
* Convert the process to an unthreaded process. The
* SINGLE_EXIT is called by exit1() or execve(), in
* both cases other threads must be retired.
*/
KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
p->p_singlethread = NULL;
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
/*
* Wait for any remaining threads to exit cpu_throw().
*/
while (p->p_exitthreads != 0) {
PROC_SUNLOCK(p);
PROC_UNLOCK(p);
sched_relinquish(td);
PROC_LOCK(p);
PROC_SLOCK(p);
}
} else if (mode == SINGLE_BOUNDARY) {
/*
* Wait until all suspended threads are removed from
* the processors. The thread_suspend_check()
* increments p_boundary_count while it is still
* running, which makes it possible for the execve()
* to destroy vmspace while our other threads are
* still using the address space.
*
* We lock the thread, which is only allowed to
* succeed after context switch code finished using
* the address space.
*/
FOREACH_THREAD_IN_PROC(p, td2) {
if (td2 == td)
continue;
thread_lock(td2);
KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
("td %p not on boundary", td2));
KASSERT(TD_IS_SUSPENDED(td2),
("td %p is not suspended", td2));
thread_unlock(td2);
}
}
PROC_SUNLOCK(p);
return (0);
}
bool
thread_suspend_check_needed(void)
{
struct proc *p;
struct thread *td;
td = curthread;
p = td->td_proc;
PROC_LOCK_ASSERT(p, MA_OWNED);
return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
(td->td_dbgflags & TDB_SUSPEND) != 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 | immediately
*---------------+--------------------+---------------------
* 1 | thread exits | returns 1
* | | immediately
* 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;
int wakeup_swapper;
td = curthread;
p = td->td_proc;
mtx_assert(&Giant, MA_NOTOWNED);
PROC_LOCK_ASSERT(p, MA_OWNED);
while (thread_suspend_check_needed()) {
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 (EINTR);
/* 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 (ERESTART);
/*
* Ignore suspend requests if they are deferred.
*/
if ((td->td_flags & TDF_SBDRY) != 0) {
KASSERT(return_instead,
("TDF_SBDRY set for unsafe thread_suspend_check"));
return (0);
}
/*
* 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)) {
PROC_UNLOCK(p);
tidhash_remove(td);
/*
* Allow Linux emulation layer to do some work
* before thread suicide.
*/
if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
(p->p_sysent->sv_thread_detach)(td);
PROC_LOCK(p);
tdsigcleanup(td);
umtx_thread_exit(td);
PROC_SLOCK(p);
thread_stopped(p);
thread_exit();
}
PROC_SLOCK(p);
thread_stopped(p);
if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
if (p->p_numthreads == p->p_suspcount + 1) {
thread_lock(p->p_singlethread);
wakeup_swapper = thread_unsuspend_one(
p->p_singlethread, p, false);
thread_unlock(p->p_singlethread);
if (wakeup_swapper)
kick_proc0();
}
}
PROC_UNLOCK(p);
thread_lock(td);
/*
* When a thread suspends, it just
* gets taken off all queues.
*/
thread_suspend_one(td);
if (return_instead == 0) {
p->p_boundary_count++;
td->td_flags |= TDF_BOUNDARY;
}
PROC_SUNLOCK(p);
mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
thread_unlock(td);
PROC_LOCK(p);
}
return (0);
}
void
thread_suspend_switch(struct thread *td, struct proc *p)
{
KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
/*
* We implement thread_suspend_one in stages here to avoid
* dropping the proc lock while the thread lock is owned.
*/
if (p == td->td_proc) {
thread_stopped(p);
p->p_suspcount++;
}
PROC_UNLOCK(p);
thread_lock(td);
td->td_flags &= ~TDF_NEEDSUSPCHK;
TD_SET_SUSPENDED(td);
sched_sleep(td, 0);
PROC_SUNLOCK(p);
DROP_GIANT();
mi_switch(SW_VOL | SWT_SUSPEND, NULL);
thread_unlock(td);
PICKUP_GIANT();
PROC_LOCK(p);
PROC_SLOCK(p);
}
void
thread_suspend_one(struct thread *td)
{
struct proc *p;
p = td->td_proc;
PROC_SLOCK_ASSERT(p, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
p->p_suspcount++;
td->td_flags &= ~TDF_NEEDSUSPCHK;
TD_SET_SUSPENDED(td);
sched_sleep(td, 0);
}
static int
thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
TD_CLR_SUSPENDED(td);
td->td_flags &= ~TDF_ALLPROCSUSP;
if (td->td_proc == p) {
PROC_SLOCK_ASSERT(p, MA_OWNED);
p->p_suspcount--;
if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
td->td_flags &= ~TDF_BOUNDARY;
p->p_boundary_count--;
}
}
return (setrunnable(td));
}
/*
* Allow all threads blocked by single threading to continue running.
*/
void
thread_unsuspend(struct proc *p)
{
struct thread *td;
int wakeup_swapper;
PROC_LOCK_ASSERT(p, MA_OWNED);
PROC_SLOCK_ASSERT(p, MA_OWNED);
wakeup_swapper = 0;
if (!P_SHOULDSTOP(p)) {
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (TD_IS_SUSPENDED(td)) {
wakeup_swapper |= thread_unsuspend_one(td, p,
true);
}
thread_unlock(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.
*/
if (p->p_singlethread->td_proc == p) {
thread_lock(p->p_singlethread);
wakeup_swapper = thread_unsuspend_one(
p->p_singlethread, p, false);
thread_unlock(p->p_singlethread);
}
}
if (wakeup_swapper)
kick_proc0();
}
/*
* End the single threading mode..
*/
void
thread_single_end(struct proc *p, int mode)
{
struct thread *td;
int wakeup_swapper;
KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
("invalid mode %d", mode));
PROC_LOCK_ASSERT(p, MA_OWNED);
KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
(mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
("mode %d does not match P_TOTAL_STOP", mode));
KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
("thread_single_end from other thread %p %p",
curthread, p->p_singlethread));
KASSERT(mode != SINGLE_BOUNDARY ||
(p->p_flag & P_SINGLE_BOUNDARY) != 0,
("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
P_TOTAL_STOP);
PROC_SLOCK(p);
p->p_singlethread = NULL;
wakeup_swapper = 0;
/*
* If there are other threads they may 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 != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (TD_IS_SUSPENDED(td)) {
wakeup_swapper |= thread_unsuspend_one(td, p,
mode == SINGLE_BOUNDARY);
}
thread_unlock(td);
}
}
KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
("inconsistent boundary count %d", p->p_boundary_count));
PROC_SUNLOCK(p);
if (wakeup_swapper)
kick_proc0();
}
struct thread *
thread_find(struct proc *p, lwpid_t tid)
{
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
FOREACH_THREAD_IN_PROC(p, td) {
if (td->td_tid == tid)
break;
}
return (td);
}
/* Locate a thread by number; return with proc lock held. */
struct thread *
tdfind(lwpid_t tid, pid_t pid)
{
#define RUN_THRESH 16
struct thread *td;
int run = 0;
rw_rlock(&tidhash_lock);
LIST_FOREACH(td, TIDHASH(tid), td_hash) {
if (td->td_tid == tid) {
if (pid != -1 && td->td_proc->p_pid != pid) {
td = NULL;
break;
}
PROC_LOCK(td->td_proc);
if (td->td_proc->p_state == PRS_NEW) {
PROC_UNLOCK(td->td_proc);
td = NULL;
break;
}
if (run > RUN_THRESH) {
if (rw_try_upgrade(&tidhash_lock)) {
LIST_REMOVE(td, td_hash);
LIST_INSERT_HEAD(TIDHASH(td->td_tid),
td, td_hash);
rw_wunlock(&tidhash_lock);
return (td);
}
}
break;
}
run++;
}
rw_runlock(&tidhash_lock);
return (td);
}
void
tidhash_add(struct thread *td)
{
rw_wlock(&tidhash_lock);
LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
rw_wunlock(&tidhash_lock);
}
void
tidhash_remove(struct thread *td)
{
rw_wlock(&tidhash_lock);
LIST_REMOVE(td, td_hash);
rw_wunlock(&tidhash_lock);
}
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