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623daa69f9
freebsd-skq/sys/kern/kern_thread.c
Mateusz Guzik b83e94be53 thread: staticize thread_reap and move td_allocdomain 
thread_init is a much better fit as the the value is constant after
initialization.
2020-11-26 06:59:27 +00:00

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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* 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/bitstring.h>
#include <sys/epoch.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/syscallsubr.h>
#include <sys/dtrace_bsd.h>
#include <sys/sysent.h>
#include <sys/turnstile.h>
#include <sys/taskqueue.h>
#include <sys/ktr.h>
#include <sys/rwlock.h>
#include <sys/umtx.h>
#include <sys/vmmeter.h>
#include <sys/cpuset.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <sys/priv.h>
#include <security/audit/audit.h>
#include <vm/pmap.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
#include <vm/vm_phys.h>
#include <sys/eventhandler.h>
/*
* Asserts below verify the stability of struct thread and struct proc
* layout, as exposed by KBI to modules. On head, the KBI is allowed
* to drift, change to the structures must be accompanied by the
* assert update.
*
* On the stable branches after KBI freeze, conditions must not be
* violated. Typically new fields are moved to the end of the
* structures.
*/
#ifdef __amd64__
_Static_assert(offsetof(struct thread, td_flags) == 0xfc,
"struct thread KBI td_flags");
_Static_assert(offsetof(struct thread, td_pflags) == 0x104,
"struct thread KBI td_pflags");
_Static_assert(offsetof(struct thread, td_frame) == 0x4a0,
"struct thread KBI td_frame");
_Static_assert(offsetof(struct thread, td_emuldata) == 0x6b0,
"struct thread KBI td_emuldata");
_Static_assert(offsetof(struct proc, p_flag) == 0xb8,
"struct proc KBI p_flag");
_Static_assert(offsetof(struct proc, p_pid) == 0xc4,
"struct proc KBI p_pid");
_Static_assert(offsetof(struct proc, p_filemon) == 0x3c0,
"struct proc KBI p_filemon");
_Static_assert(offsetof(struct proc, p_comm) == 0x3d8,
"struct proc KBI p_comm");
_Static_assert(offsetof(struct proc, p_emuldata) == 0x4b8,
"struct proc KBI p_emuldata");
#endif
#ifdef __i386__
_Static_assert(offsetof(struct thread, td_flags) == 0x98,
"struct thread KBI td_flags");
_Static_assert(offsetof(struct thread, td_pflags) == 0xa0,
"struct thread KBI td_pflags");
_Static_assert(offsetof(struct thread, td_frame) == 0x300,
"struct thread KBI td_frame");
_Static_assert(offsetof(struct thread, td_emuldata) == 0x344,
"struct thread KBI td_emuldata");
_Static_assert(offsetof(struct proc, p_flag) == 0x6c,
"struct proc KBI p_flag");
_Static_assert(offsetof(struct proc, p_pid) == 0x78,
"struct proc KBI p_pid");
_Static_assert(offsetof(struct proc, p_filemon) == 0x26c,
"struct proc KBI p_filemon");
_Static_assert(offsetof(struct proc, p_comm) == 0x280,
"struct proc KBI p_comm");
_Static_assert(offsetof(struct proc, p_emuldata) == 0x30c,
"struct proc KBI p_emuldata");
#endif
SDT_PROVIDER_DECLARE(proc);
SDT_PROBE_DEFINE(proc, , , lwp__exit);
/*
* thread related storage.
*/
static uma_zone_t thread_zone;
struct thread_domain_data {
struct thread *tdd_zombies;
int tdd_reapticks;
} __aligned(CACHE_LINE_SIZE);
static struct thread_domain_data thread_domain_data[MAXMEMDOM];
static struct task thread_reap_task;
static struct callout thread_reap_callout;
static void thread_zombie(struct thread *);
static void thread_reap(void);
static void thread_reap_all(void);
static void thread_reap_task_cb(void *, int);
static void thread_reap_callout_cb(void *);
static int thread_unsuspend_one(struct thread *td, struct proc *p,
bool boundary);
static void thread_free_batched(struct thread *td);
static __exclusive_cache_line struct mtx tid_lock;
static bitstr_t *tid_bitmap;
static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
static int maxthread;
SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN,
&maxthread, 0, "Maximum number of threads");
static __exclusive_cache_line int nthreads;
static LIST_HEAD(tidhashhead, thread) *tidhashtbl;
static u_long tidhash;
static u_long tidhashlock;
static struct rwlock *tidhashtbl_lock;
#define TIDHASH(tid) (&tidhashtbl[(tid) & tidhash])
#define TIDHASHLOCK(tid) (&tidhashtbl_lock[(tid) & tidhashlock])
EVENTHANDLER_LIST_DEFINE(thread_ctor);
EVENTHANDLER_LIST_DEFINE(thread_dtor);
EVENTHANDLER_LIST_DEFINE(thread_init);
EVENTHANDLER_LIST_DEFINE(thread_fini);
static bool
thread_count_inc_try(void)
{
int nthreads_new;
nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
if (nthreads_new >= maxthread - 100) {
if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
nthreads_new >= maxthread) {
atomic_subtract_int(&nthreads, 1);
return (false);
}
}
return (true);
}
static bool
thread_count_inc(void)
{
static struct timeval lastfail;
static int curfail;
thread_reap();
if (thread_count_inc_try()) {
return (true);
}
thread_reap_all();
if (thread_count_inc_try()) {
return (true);
}
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxthread limit exceeded by uid %u "
"(pid %d); consider increasing kern.maxthread\n",
curthread->td_ucred->cr_ruid, curproc->p_pid);
}
return (false);
}
static void
thread_count_sub(int n)
{
atomic_subtract_int(&nthreads, n);
}
static void
thread_count_dec(void)
{
thread_count_sub(1);
}
static lwpid_t
tid_alloc(void)
{
static lwpid_t trytid;
lwpid_t tid;
mtx_lock(&tid_lock);
/*
* It is an invariant that the bitmap is big enough to hold maxthread
* IDs. If we got to this point there has to be at least one free.
*/
if (trytid >= maxthread)
trytid = 0;
bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
if (tid == -1) {
KASSERT(trytid != 0, ("unexpectedly ran out of IDs"));
trytid = 0;
bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
KASSERT(tid != -1, ("unexpectedly ran out of IDs"));
}
bit_set(tid_bitmap, tid);
trytid = tid + 1;
mtx_unlock(&tid_lock);
return (tid + NO_PID);
}
static void
tid_free_locked(lwpid_t rtid)
{
lwpid_t tid;
mtx_assert(&tid_lock, MA_OWNED);
KASSERT(rtid >= NO_PID,
("%s: invalid tid %d\n", __func__, rtid));
tid = rtid - NO_PID;
KASSERT(bit_test(tid_bitmap, tid) != 0,
("thread ID %d not allocated\n", rtid));
bit_clear(tid_bitmap, tid);
}
static void
tid_free(lwpid_t rtid)
{
mtx_lock(&tid_lock);
tid_free_locked(rtid);
mtx_unlock(&tid_lock);
}
static void
tid_free_batch(lwpid_t *batch, int n)
{
int i;
mtx_lock(&tid_lock);
for (i = 0; i < n; i++) {
tid_free_locked(batch[i]);
}
mtx_unlock(&tid_lock);
}
/*
* Batching for thread reapping.
*/
struct tidbatch {
lwpid_t tab[16];
int n;
};
static void
tidbatch_prep(struct tidbatch *tb)
{
tb->n = 0;
}
static void
tidbatch_add(struct tidbatch *tb, struct thread *td)
{
KASSERT(tb->n < nitems(tb->tab),
("%s: count too high %d", __func__, tb->n));
tb->tab[tb->n] = td->td_tid;
tb->n++;
}
static void
tidbatch_process(struct tidbatch *tb)
{
KASSERT(tb->n <= nitems(tb->tab),
("%s: count too high %d", __func__, tb->n));
if (tb->n == nitems(tb->tab)) {
tid_free_batch(tb->tab, tb->n);
tb->n = 0;
}
}
static void
tidbatch_final(struct tidbatch *tb)
{
KASSERT(tb->n <= nitems(tb->tab),
("%s: count too high %d", __func__, tb->n));
if (tb->n != 0) {
tid_free_batch(tb->tab, tb->n);
}
}
/*
* 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_lastcpu = 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.
*/
td->td_critnest = 1;
td->td_lend_user_pri = PRI_MAX;
#ifdef AUDIT
audit_thread_alloc(td);
#endif
#ifdef KDTRACE_HOOKS
kdtrace_thread_ctor(td);
#endif
umtx_thread_alloc(td);
MPASS(td->td_sel == NULL);
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
#ifdef KDTRACE_HOOKS
kdtrace_thread_dtor(td);
#endif
/* Free all OSD associated to this thread. */
osd_thread_exit(td);
td_softdep_cleanup(td);
MPASS(td->td_su == NULL);
seltdfini(td);
}
/*
* 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_allocdomain = vm_phys_domain(vtophys(td));
td->td_sleepqueue = sleepq_alloc();
td->td_turnstile = turnstile_alloc();
td->td_rlqe = NULL;
EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
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_DIRECT_INVOKE(thread_fini, td);
rlqentry_free(td->td_rlqe);
turnstile_free(td->td_turnstile);
sleepq_free(td->td_sleepqueue);
umtx_thread_fini(td);
MPASS(td->td_sel == NULL);
}
/*
* 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);
}
extern int max_threads_per_proc;
/*
* Initialize global thread allocation resources.
*/
void
threadinit(void)
{
u_long i;
lwpid_t tid0;
uint32_t flags;
/*
* Place an upper limit on threads which can be allocated.
*
* Note that other factors may make the de facto limit much lower.
*
* Platform limits are somewhat arbitrary but deemed "more than good
* enough" for the foreseable future.
*/
if (maxthread == 0) {
#ifdef _LP64
maxthread = MIN(maxproc * max_threads_per_proc, 1000000);
#else
maxthread = MIN(maxproc * max_threads_per_proc, 100000);
#endif
}
mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK);
/*
* Handle thread0.
*/
thread_count_inc();
tid0 = tid_alloc();
if (tid0 != THREAD0_TID)
panic("tid0 %d != %d\n", tid0, THREAD0_TID);
flags = UMA_ZONE_NOFREE;
#ifdef __aarch64__
/*
* Force thread structures to be allocated from the direct map.
* Otherwise, superpage promotions and demotions may temporarily
* invalidate thread structure mappings. For most dynamically allocated
* structures this is not a problem, but translation faults cannot be
* handled without accessing curthread.
*/
flags |= UMA_ZONE_CONTIG;
#endif
thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
thread_ctor, thread_dtor, thread_init, thread_fini,
32 - 1, flags);
tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
tidhashlock = (tidhash + 1) / 64;
if (tidhashlock > 0)
tidhashlock--;
tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1),
M_TIDHASH, M_WAITOK | M_ZERO);
for (i = 0; i < tidhashlock + 1; i++)
rw_init(&tidhashtbl_lock[i], "tidhash");
TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL);
callout_init(&thread_reap_callout, 1);
callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
}
/*
* Place an unused thread on the zombie list.
*/
void
thread_zombie(struct thread *td)
{
struct thread_domain_data *tdd;
struct thread *ztd;
tdd = &thread_domain_data[td->td_allocdomain];
ztd = atomic_load_ptr(&tdd->tdd_zombies);
for (;;) {
td->td_zombie = ztd;
if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
(uintptr_t *)&ztd, (uintptr_t)td))
break;
continue;
}
}
/*
* 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 zombies from passed domain.
*/
static void
thread_reap_domain(struct thread_domain_data *tdd)
{
struct thread *itd, *ntd;
struct tidbatch tidbatch;
struct credbatch credbatch;
int tdcount;
struct plimit *lim;
int limcount;
/*
* Reading upfront is pessimal if followed by concurrent atomic_swap,
* but most of the time the list is empty.
*/
if (tdd->tdd_zombies == NULL)
return;
itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
(uintptr_t)NULL);
if (itd == NULL)
return;
/*
* Multiple CPUs can get here, the race is fine as ticks is only
* advisory.
*/
tdd->tdd_reapticks = ticks;
tidbatch_prep(&tidbatch);
credbatch_prep(&credbatch);
tdcount = 0;
lim = NULL;
limcount = 0;
while (itd != NULL) {
ntd = itd->td_zombie;
EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
tidbatch_add(&tidbatch, itd);
credbatch_add(&credbatch, itd);
MPASS(itd->td_limit != NULL);
if (lim != itd->td_limit) {
if (limcount != 0) {
lim_freen(lim, limcount);
limcount = 0;
}
}
lim = itd->td_limit;
limcount++;
thread_free_batched(itd);
tidbatch_process(&tidbatch);
credbatch_process(&credbatch);
tdcount++;
if (tdcount == 32) {
thread_count_sub(tdcount);
tdcount = 0;
}
itd = ntd;
}
tidbatch_final(&tidbatch);
credbatch_final(&credbatch);
if (tdcount != 0) {
thread_count_sub(tdcount);
}
MPASS(limcount != 0);
lim_freen(lim, limcount);
}
/*
* Reap zombies from all domains.
*/
static void
thread_reap_all(void)
{
struct thread_domain_data *tdd;
int i, domain;
domain = PCPU_GET(domain);
for (i = 0; i < vm_ndomains; i++) {
tdd = &thread_domain_data[(i + domain) % vm_ndomains];
thread_reap_domain(tdd);
}
}
/*
* Reap zombies from local domain.
*/
static void
thread_reap(void)
{
struct thread_domain_data *tdd;
int domain;
domain = PCPU_GET(domain);
tdd = &thread_domain_data[domain];
thread_reap_domain(tdd);
}
static void
thread_reap_task_cb(void *arg __unused, int pending __unused)
{
thread_reap_all();
}
static void
thread_reap_callout_cb(void *arg __unused)
{
struct thread_domain_data *tdd;
int i, cticks, lticks;
bool wantreap;
wantreap = false;
cticks = atomic_load_int(&ticks);
for (i = 0; i < vm_ndomains; i++) {
tdd = &thread_domain_data[i];
lticks = tdd->tdd_reapticks;
if (tdd->tdd_zombies != NULL &&
(u_int)(cticks - lticks) > 5 * hz) {
wantreap = true;
break;
}
}
if (wantreap)
taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
}
/*
* Allocate a thread.
*/
struct thread *
thread_alloc(int pages)
{
struct thread *td;
lwpid_t tid;
if (!thread_count_inc()) {
return (NULL);
}
tid = tid_alloc();
td = 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);
tid_free(tid);
thread_count_dec();
return (NULL);
}
td->td_tid = tid;
cpu_thread_alloc(td);
EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
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.
*/
static void
thread_free_batched(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);
callout_drain(&td->td_slpcallout);
/*
* Freeing handled by the caller.
*/
td->td_tid = -1;
uma_zfree(thread_zone, td);
}
void
thread_free(struct thread *td)
{
lwpid_t tid;
EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
tid = td->td_tid;
thread_free_batched(td);
tid_free(tid);
thread_count_dec();
}
void
thread_cow_get_proc(struct thread *newtd, struct proc *p)
{
PROC_LOCK_ASSERT(p, MA_OWNED);
newtd->td_realucred = crcowget(p->p_ucred);
newtd->td_ucred = newtd->td_realucred;
newtd->td_limit = lim_hold(p->p_limit);
newtd->td_cowgen = p->p_cowgen;
}
void
thread_cow_get(struct thread *newtd, struct thread *td)
{
MPASS(td->td_realucred == td->td_ucred);
newtd->td_realucred = crcowget(td->td_realucred);
newtd->td_ucred = newtd->td_realucred;
newtd->td_limit = lim_hold(td->td_limit);
newtd->td_cowgen = td->td_cowgen;
}
void
thread_cow_free(struct thread *td)
{
if (td->td_realucred != NULL)
crcowfree(td);
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;
oldlimit = NULL;
PROC_LOCK(p);
oldcred = crcowsync();
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);
SDT_PROBE0(proc, , , lwp__exit);
KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
MPASS(td->td_realucred == td->td_ucred);
/*
* 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);
/*
* 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);
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);
PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
} else if (PMC_SYSTEM_SAMPLING_ACTIVE())
PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
#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);
VM_CNT_INC(v_swtch);
/* Save our resource usage in our process. */
td->td_ru.ru_nvcsw++;
ruxagg_locked(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);
callout_drain(&td->td_slpcallout);
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]);
#ifdef EPOCH_TRACE
SLIST_INIT(&td->td_epochs);
#endif
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);
#ifdef EPOCH_TRACE
MPASS(SLIST_EMPTY(&td->td_epochs));
#endif
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;
/*
* Since the thread lock is dropped by the scheduler we have
* to retry to check for races.
*/
restart:
switch (mode) {
case SINGLE_EXIT:
if (TD_IS_SUSPENDED(td2)) {
wakeup_swapper |= thread_unsuspend_one(td2, p, true);
thread_lock(td2);
goto restart;
}
if (TD_CAN_ABORT(td2)) {
wakeup_swapper |= sleepq_abort(td2, EINTR);
return (wakeup_swapper);
}
break;
case SINGLE_BOUNDARY:
case SINGLE_NO_EXIT:
if (TD_IS_SUSPENDED(td2) &&
(td2->td_flags & TDF_BOUNDARY) == 0) {
wakeup_swapper |= thread_unsuspend_one(td2, p, false);
thread_lock(td2);
goto restart;
}
if (TD_CAN_ABORT(td2)) {
wakeup_swapper |= sleepq_abort(td2, ERESTART);
return (wakeup_swapper);
}
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);
thread_lock(td2);
goto restart;
}
if (TD_CAN_ABORT(td2)) {
if ((td2->td_flags & TDF_SBDRY) == 0) {
thread_suspend_one(td2);
td2->td_flags |= TDF_ALLPROCSUSP;
} else {
wakeup_swapper |= sleepq_abort(td2, ERESTART);
return (wakeup_swapper);
}
}
break;
default:
break;
}
thread_unlock(td2);
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);
thread_unlock(td2);
#endif
} else
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.
* It is safe to access p->p_singlethread unlocked
* because it can only be set to our address 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"));
KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
(TDF_SEINTR | TDF_SERESTART),
("both TDF_SEINTR and TDF_SERESTART"));
return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 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);
/*
* 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);
umtx_thread_exit(td);
kern_thr_exit(td);
panic("stopped thread did not 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);
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);
PROC_LOCK(p);
}
return (0);
}
/*
* Check for possible stops and suspensions while executing a
* casueword or similar transiently failing operation.
*
* The sleep argument controls whether the function can handle a stop
* request itself or it should return ERESTART and the request is
* proceed at the kernel/user boundary in ast.
*
* Typically, when retrying due to casueword(9) failure (rv == 1), we
* should handle the stop requests there, with exception of cases when
* the thread owns a kernel resource, for instance busied the umtx
* key, or when functions return immediately if thread_check_susp()
* returned non-zero. On the other hand, retrying the whole lock
* operation, we better not stop there but delegate the handling to
* ast.
*
* If the request is for thread termination P_SINGLE_EXIT, we cannot
* handle it at all, and simply return EINTR.
*/
int
thread_check_susp(struct thread *td, bool sleep)
{
struct proc *p;
int error;
/*
* The check for TDF_NEEDSUSPCHK is racy, but it is enough to
* eventually break the lockstep loop.
*/
if ((td->td_flags & TDF_NEEDSUSPCHK) == 0)
return (0);
error = 0;
p = td->td_proc;
PROC_LOCK(p);
if (p->p_flag & P_SINGLE_EXIT)
error = EINTR;
else if (P_SHOULDSTOP(p) ||
((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND)))
error = sleep ? thread_suspend_check(0) : ERESTART;
PROC_UNLOCK(p);
return (error);
}
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);
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, 0));
}
/*
* 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);
} else
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);
}
}
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);
} else
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();
}
/*
* Locate a thread by number and return with proc lock held.
*
* thread exit establishes proc -> tidhash lock ordering, but lookup
* takes tidhash first and needs to return locked proc.
*
* The problem is worked around by relying on type-safety of both
* structures and doing the work in 2 steps:
* - tidhash-locked lookup which saves both thread and proc pointers
* - proc-locked verification that the found thread still matches
*/
static bool
tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp)
{
#define RUN_THRESH 16
struct proc *p;
struct thread *td;
int run;
bool locked;
run = 0;
rw_rlock(TIDHASHLOCK(tid));
locked = true;
LIST_FOREACH(td, TIDHASH(tid), td_hash) {
if (td->td_tid != tid) {
run++;
continue;
}
p = td->td_proc;
if (pid != -1 && p->p_pid != pid) {
td = NULL;
break;
}
if (run > RUN_THRESH) {
if (rw_try_upgrade(TIDHASHLOCK(tid))) {
LIST_REMOVE(td, td_hash);
LIST_INSERT_HEAD(TIDHASH(td->td_tid),
td, td_hash);
rw_wunlock(TIDHASHLOCK(tid));
locked = false;
break;
}
}
break;
}
if (locked)
rw_runlock(TIDHASHLOCK(tid));
if (td == NULL)
return (false);
*pp = p;
*tdp = td;
return (true);
}
struct thread *
tdfind(lwpid_t tid, pid_t pid)
{
struct proc *p;
struct thread *td;
td = curthread;
if (td->td_tid == tid) {
if (pid != -1 && td->td_proc->p_pid != pid)
return (NULL);
PROC_LOCK(td->td_proc);
return (td);
}
for (;;) {
if (!tdfind_hash(tid, pid, &p, &td))
return (NULL);
PROC_LOCK(p);
if (td->td_tid != tid) {
PROC_UNLOCK(p);
continue;
}
if (td->td_proc != p) {
PROC_UNLOCK(p);
continue;
}
if (p->p_state == PRS_NEW) {
PROC_UNLOCK(p);
return (NULL);
}
return (td);
}
}
void
tidhash_add(struct thread *td)
{
rw_wlock(TIDHASHLOCK(td->td_tid));
LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
rw_wunlock(TIDHASHLOCK(td->td_tid));
}
void
tidhash_remove(struct thread *td)
{
rw_wlock(TIDHASHLOCK(td->td_tid));
LIST_REMOVE(td, td_hash);
rw_wunlock(TIDHASHLOCK(td->td_tid));
}
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