/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1982, 1986, 1990, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ktrace.h"
#include "opt_sched.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/blockcount.h>
#include <sys/condvar.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vmmeter.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#ifdef EPOCH_TRACE
#include <sys/epoch.h>
#endif
#include <machine/cpu.h>
static void synch_setup(void *dummy);
SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
NULL);
int hogticks;
static const char pause_wchan[MAXCPU];
static struct callout loadav_callout;
struct loadavg averunnable =
{ {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
/*
* Constants for averages over 1, 5, and 15 minutes
* when sampling at 5 second intervals.
*/
static fixpt_t cexp[3] = {
0.9200444146293232 * FSCALE, /* exp(-1/12) */
0.9834714538216174 * FSCALE, /* exp(-1/60) */
0.9944598480048967 * FSCALE, /* exp(-1/180) */
};
/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE,
"Fixed-point scale factor used for calculating load average values");
static void loadav(void *arg);
SDT_PROVIDER_DECLARE(sched);
SDT_PROBE_DEFINE(sched, , , preempt);
static void
sleepinit(void *unused)
{
hogticks = (hz / 10) * 2; /* Default only. */
init_sleepqueues();
}
/*
* vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
* it is available.
*/
SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, NULL);
/*
* General sleep call. Suspends the current thread until a wakeup is
* performed on the specified identifier. The thread will then be made
* runnable with the specified priority. Sleeps at most sbt units of time
* (0 means no timeout). If pri includes the PCATCH flag, let signals
* interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if
* awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
* signal becomes pending, ERESTART is returned if the current system
* call should be restarted if possible, and EINTR is returned if the system
* call should be interrupted by the signal (return EINTR).
*
* The lock argument is unlocked before the caller is suspended, and
* re-locked before _sleep() returns. If priority includes the PDROP
* flag the lock is not re-locked before returning.
*/
int
_sleep(const void *ident, struct lock_object *lock, int priority,
const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
{
struct thread *td;
struct lock_class *class;
uintptr_t lock_state;
int catch, pri, rval, sleepq_flags;
WITNESS_SAVE_DECL(lock_witness);
td = curthread;
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(1, 0, wmesg);
#endif
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
"Sleeping on \"%s\"", wmesg);
KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL,
("sleeping without a lock"));
KASSERT(ident != NULL, ("_sleep: NULL ident"));
KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
if (priority & PDROP)
KASSERT(lock != NULL && lock != &Giant.lock_object,
("PDROP requires a non-Giant lock"));
if (lock != NULL)
class = LOCK_CLASS(lock);
else
class = NULL;
if (SCHEDULER_STOPPED_TD(td)) {
if (lock != NULL && priority & PDROP)
class->lc_unlock(lock);
return (0);
}
catch = priority & PCATCH;
pri = priority & PRIMASK;
KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] &&
(uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1])
sleepq_flags = SLEEPQ_PAUSE;
else
sleepq_flags = SLEEPQ_SLEEP;
if (catch)
sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
sleepq_lock(ident);
CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
if (lock == &Giant.lock_object)
mtx_assert(&Giant, MA_OWNED);
DROP_GIANT();
if (lock != NULL && lock != &Giant.lock_object &&
!(class->lc_flags & LC_SLEEPABLE)) {
WITNESS_SAVE(lock, lock_witness);
lock_state = class->lc_unlock(lock);
} else
/* GCC needs to follow the Yellow Brick Road */
lock_state = -1;
/*
* We put ourselves on the sleep queue and start our timeout
* before calling thread_suspend_check, as we could stop there,
* and a wakeup or a SIGCONT (or both) could occur while we were
* stopped without resuming us. Thus, we must be ready for sleep
* when cursig() is called. If the wakeup happens while we're
* stopped, then td will no longer be on a sleep queue upon
* return from cursig().
*/
sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
if (sbt != 0)
sleepq_set_timeout_sbt(ident, sbt, pr, flags);
if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
sleepq_release(ident);
WITNESS_SAVE(lock, lock_witness);
lock_state = class->lc_unlock(lock);
sleepq_lock(ident);
}
if (sbt != 0 && catch)
rval = sleepq_timedwait_sig(ident, pri);
else if (sbt != 0)
rval = sleepq_timedwait(ident, pri);
else if (catch)
rval = sleepq_wait_sig(ident, pri);
else {
sleepq_wait(ident, pri);
rval = 0;
}
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(0, 0, wmesg);
#endif
PICKUP_GIANT();
if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
class->lc_lock(lock, lock_state);
WITNESS_RESTORE(lock, lock_witness);
}
return (rval);
}
int
msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg,
sbintime_t sbt, sbintime_t pr, int flags)
{
struct thread *td;
int rval;
WITNESS_SAVE_DECL(mtx);
td = curthread;
KASSERT(mtx != NULL, ("sleeping without a mutex"));
KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
if (SCHEDULER_STOPPED_TD(td))
return (0);
sleepq_lock(ident);
CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
DROP_GIANT();
mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
WITNESS_SAVE(&mtx->lock_object, mtx);
mtx_unlock_spin(mtx);
/*
* We put ourselves on the sleep queue and start our timeout.
*/
sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
if (sbt != 0)
sleepq_set_timeout_sbt(ident, sbt, pr, flags);
/*
* Can't call ktrace with any spin locks held so it can lock the
* ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
* any spin lock. Thus, we have to drop the sleepq spin lock while
* we handle those requests. This is safe since we have placed our
* thread on the sleep queue already.
*/
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW)) {
sleepq_release(ident);
ktrcsw(1, 0, wmesg);
sleepq_lock(ident);
}
#endif
#ifdef WITNESS
sleepq_release(ident);
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
wmesg);
sleepq_lock(ident);
#endif
if (sbt != 0)
rval = sleepq_timedwait(ident, 0);
else {
sleepq_wait(ident, 0);
rval = 0;
}
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(0, 0, wmesg);
#endif
PICKUP_GIANT();
mtx_lock_spin(mtx);
WITNESS_RESTORE(&mtx->lock_object, mtx);
return (rval);
}
/*
* pause_sbt() delays the calling thread by the given signed binary
* time. During cold bootup, pause_sbt() uses the DELAY() function
* instead of the _sleep() function to do the waiting. The "sbt"
* argument must be greater than or equal to zero. A "sbt" value of
* zero is equivalent to a "sbt" value of one tick.
*/
int
pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
{
KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0"));
/* silently convert invalid timeouts */
if (sbt == 0)
sbt = tick_sbt;
if ((cold && curthread == &thread0) || kdb_active ||
SCHEDULER_STOPPED()) {
/*
* We delay one second at a time to avoid overflowing the
* system specific DELAY() function(s):
*/
while (sbt >= SBT_1S) {
DELAY(1000000);
sbt -= SBT_1S;
}
/* Do the delay remainder, if any */
sbt = howmany(sbt, SBT_1US);
if (sbt > 0)
DELAY(sbt);
return (EWOULDBLOCK);
}
return (_sleep(&pause_wchan[curcpu], NULL,
(flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags));
}
/*
* Make all threads sleeping on the specified identifier runnable.
*/
void
wakeup(const void *ident)
{
int wakeup_swapper;
sleepq_lock(ident);
wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
sleepq_release(ident);
if (wakeup_swapper) {
KASSERT(ident != &proc0,
("wakeup and wakeup_swapper and proc0"));
kick_proc0();
}
}
/*
* Make a thread sleeping on the specified identifier runnable.
* May wake more than one thread if a target thread is currently
* swapped out.
*/
void
wakeup_one(const void *ident)
{
int wakeup_swapper;
sleepq_lock(ident);
wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
if (wakeup_swapper)
kick_proc0();
}
void
wakeup_any(const void *ident)
{
int wakeup_swapper;
sleepq_lock(ident);
wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR |
SLEEPQ_DROP, 0, 0);
if (wakeup_swapper)
kick_proc0();
}
/*
* Signal sleeping waiters after the counter has reached zero.
*/
void
_blockcount_wakeup(blockcount_t *bc, u_int old)
{
KASSERT(_BLOCKCOUNT_WAITERS(old),
("%s: no waiters on %p", __func__, bc));
if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0))
wakeup(bc);
}
/*
* Wait for a wakeup or a signal. This does not guarantee that the count is
* still zero on return. Callers wanting a precise answer should use
* blockcount_wait() with an interlock.
*
* If there is no work to wait for, return 0. If the sleep was interrupted by a
* signal, return EINTR or ERESTART, and return EAGAIN otherwise.
*/
int
_blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
int prio)
{
void *wchan;
uintptr_t lock_state;
u_int old;
int ret;
bool catch, drop;
KASSERT(lock != &Giant.lock_object,
("%s: cannot use Giant as the interlock", __func__));
catch = (prio & PCATCH) != 0;
drop = (prio & PDROP) != 0;
prio &= PRIMASK;
/*
* Synchronize with the fence in blockcount_release(). If we end up
* waiting, the sleepqueue lock acquisition will provide the required
* side effects.
*
* If there is no work to wait for, but waiters are present, try to put
* ourselves to sleep to avoid jumping ahead.
*/
if (atomic_load_acq_int(&bc->__count) == 0) {
if (lock != NULL && drop)
LOCK_CLASS(lock)->lc_unlock(lock);
return (0);
}
lock_state = 0;
wchan = bc;
sleepq_lock(wchan);
DROP_GIANT();
if (lock != NULL)
lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
old = blockcount_read(bc);
ret = 0;
do {
if (_BLOCKCOUNT_COUNT(old) == 0) {
sleepq_release(wchan);
goto out;
}
if (_BLOCKCOUNT_WAITERS(old))
break;
} while (!atomic_fcmpset_int(&bc->__count, &old,
old | _BLOCKCOUNT_WAITERS_FLAG));
sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
if (catch)
ret = sleepq_wait_sig(wchan, prio);
else
sleepq_wait(wchan, prio);
if (ret == 0)
ret = EAGAIN;
out:
PICKUP_GIANT();
if (lock != NULL && !drop)
LOCK_CLASS(lock)->lc_lock(lock, lock_state);
return (ret);
}
static void
kdb_switch(void)
{
thread_unlock(curthread);
kdb_backtrace();
kdb_reenter();
panic("%s: did not reenter debugger", __func__);
}
/*
* The machine independent parts of context switching.
*
* The thread lock is required on entry and is no longer held on return.
*/
void
mi_switch(int flags)
{
uint64_t runtime, new_switchtime;
struct thread *td;
td = curthread; /* XXX */
THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
#ifdef INVARIANTS
if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
mtx_assert(&Giant, MA_NOTOWNED);
#endif
KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(),
("mi_switch: switch in a critical section"));
KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
("mi_switch: switch must be voluntary or involuntary"));
/*
* Don't perform context switches from the debugger.
*/
if (kdb_active)
kdb_switch();
if (SCHEDULER_STOPPED_TD(td))
return;
if (flags & SW_VOL) {
td->td_ru.ru_nvcsw++;
td->td_swvoltick = ticks;
} else {
td->td_ru.ru_nivcsw++;
td->td_swinvoltick = ticks;
}
#ifdef SCHED_STATS
SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
#endif
/*
* Compute the amount of time during which the current
* thread was running, and add that to its total so far.
*/
new_switchtime = cpu_ticks();
runtime = new_switchtime - PCPU_GET(switchtime);
td->td_runtime += runtime;
td->td_incruntime += runtime;
PCPU_SET(switchtime, new_switchtime);
td->td_generation++; /* bump preempt-detect counter */
VM_CNT_INC(v_swtch);
PCPU_SET(switchticks, ticks);
CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
#ifdef KDTRACE_HOOKS
if (SDT_PROBES_ENABLED() &&
((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
(flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)))
SDT_PROBE0(sched, , , preempt);
#endif
sched_switch(td, flags);
CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
/*
* If the last thread was exiting, finish cleaning it up.
*/
if ((td = PCPU_GET(deadthread))) {
PCPU_SET(deadthread, NULL);
thread_stash(td);
}
spinlock_exit();
}
/*
* Change thread state to be runnable, placing it on the run queue if
* it is in memory. If it is swapped out, return true so our caller
* will know to awaken the swapper.
*
* Requires the thread lock on entry, drops on exit.
*/
int
setrunnable(struct thread *td, int srqflags)
{
int swapin;
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
swapin = 0;
switch (TD_GET_STATE(td)) {
case TDS_RUNNING:
case TDS_RUNQ:
break;
case TDS_CAN_RUN:
KASSERT((td->td_flags & TDF_INMEM) != 0,
("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X",
td, td->td_flags, td->td_inhibitors));
/* unlocks thread lock according to flags */
sched_wakeup(td, srqflags);
return (0);
case TDS_INHIBITED:
/*
* If we are only inhibited because we are swapped out
* arrange to swap in this process.
*/
if (td->td_inhibitors == TDI_SWAPPED &&
(td->td_flags & TDF_SWAPINREQ) == 0) {
td->td_flags |= TDF_SWAPINREQ;
swapin = 1;
}
break;
default:
panic("setrunnable: state 0x%x", TD_GET_STATE(td));
}
if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0)
thread_unlock(td);
return (swapin);
}
/*
* Compute a tenex style load average of a quantity on
* 1, 5 and 15 minute intervals.
*/
static void
loadav(void *arg)
{
int i, nrun;
struct loadavg *avg;
nrun = sched_load();
avg = &averunnable;
for (i = 0; i < 3; i++)
avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
/*
* Schedule the next update to occur after 5 seconds, but add a
* random variation to avoid synchronisation with processes that
* run at regular intervals.
*/
callout_reset_sbt(&loadav_callout,
SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
}
/* ARGSUSED */
static void
synch_setup(void *dummy)
{
callout_init(&loadav_callout, 1);
/* Kick off timeout driven events by calling first time. */
loadav(NULL);
}
int
should_yield(void)
{
return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
}
void
maybe_yield(void)
{
if (should_yield())
kern_yield(PRI_USER);
}
void
kern_yield(int prio)
{
struct thread *td;
td = curthread;
DROP_GIANT();
thread_lock(td);
if (prio == PRI_USER)
prio = td->td_user_pri;
if (prio >= 0)
sched_prio(td, prio);
mi_switch(SW_VOL | SWT_RELINQUISH);
PICKUP_GIANT();
}
/*
* General purpose yield system call.
*/
int
sys_yield(struct thread *td, struct yield_args *uap)
{
thread_lock(td);
if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
sched_prio(td, PRI_MAX_TIMESHARE);
mi_switch(SW_VOL | SWT_RELINQUISH);
td->td_retval[0] = 0;
return (0);
}
