67ba867827
turnstile_unpend(). A racing thread that does not have TDI_LOCK set may either be running on another CPU or it may be sitting on a run queue if it was preempted during the very small window in turnstile_wait() between unlocking the turnstile chain lock and locking sched_lock.
728 lines
21 KiB
C
728 lines
21 KiB
C
/*-
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* Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Berkeley Software Design Inc's name may not be used to endorse or
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* promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
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* and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
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*/
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/*
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* Implementation of turnstiles used to hold queue of threads blocked on
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* non-sleepable locks. Sleepable locks use condition variables to
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* implement their queues. Turnstiles differ from a sleep queue in that
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* turnstile queue's are assigned to a lock held by an owning thread. Thus,
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* when one thread is enqueued onto a turnstile, it can lend its priority
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* to the owning thread.
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*
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* We wish to avoid bloating locks with an embedded turnstile and we do not
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* want to use back-pointers in the locks for the same reason. Thus, we
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* use a similar approach to that of Solaris 7 as described in Solaris
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* Internals by Jim Mauro and Richard McDougall. Turnstiles are looked up
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* in a hash table based on the address of the lock. Each entry in the
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* hash table is a linked-lists of turnstiles and is called a turnstile
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* chain. Each chain contains a spin mutex that protects all of the
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* turnstiles in the chain.
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*
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* Each time a thread is created, a turnstile is malloc'd and attached to
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* that thread. When a thread blocks on a lock, if it is the first thread
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* to block, it lends its turnstile to the lock. If the lock already has
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* a turnstile, then it gives its turnstile to the lock's turnstile's free
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* list. When a thread is woken up, it takes a turnstile from the free list
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* if there are any other waiters. If it is the only thread blocked on the
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* lock, then it reclaims the turnstile associated with the lock and removes
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* it from the hash table.
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*
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* XXX: We should probably implement some sort of sleep queue that condition
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* variables and sleepqueue's share. On Solaris condition variables are
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* implemented using a hash table of sleep queues similar to our current
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* sleep queues. We might want to investigate doing that ourselves.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/queue.h>
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#include <sys/resourcevar.h>
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#include <sys/turnstile.h>
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#include <sys/sched.h>
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/*
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* Constants for the hash table of turnstile chains. TC_SHIFT is a magic
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* number chosen because the sleep queue's use the same value for the
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* shift. Basically, we ignore the lower 8 bits of the address.
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* TC_TABLESIZE must be a power of two for TC_MASK to work properly.
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*/
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#define TC_TABLESIZE 128 /* Must be power of 2. */
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#define TC_MASK (TC_TABLESIZE - 1)
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#define TC_SHIFT 8
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#define TC_HASH(lock) (((uintptr_t)(lock) >> TC_SHIFT) & TC_MASK)
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#define TC_LOOKUP(lock) &turnstile_chains[TC_HASH(lock)]
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/*
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* There are three different lists of turnstiles as follows. The list
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* connected by ts_link entries is a per-thread list of all the turnstiles
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* attached to locks that we own. This is used to fixup our priority when
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* a lock is released. The other two lists use the ts_hash entries. The
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* first of these two is turnstile chain list that a turnstile is on when
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* it is attached to a lock. The second list to use ts_hash is the free
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* list hung off a turnstile that is attached to a lock.
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*
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* Each turnstile contains two lists of threads. The ts_blocked list is
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* a linked list of threads blocked on the turnstile's lock. The
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* ts_pending list is a linked list of threads previously awoken by
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* turnstile_signal() or turnstile_wait() that are waiting to be put on
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* the run queue.
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*
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* Locking key:
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* c - turnstile chain lock
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* q - td_contested lock
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*/
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struct turnstile {
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TAILQ_HEAD(, thread) ts_blocked; /* (c + q) Blocked threads. */
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TAILQ_HEAD(, thread) ts_pending; /* (c) Pending threads. */
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LIST_ENTRY(turnstile) ts_hash; /* (c) Chain and free list. */
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LIST_ENTRY(turnstile) ts_link; /* (q) Contested locks. */
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LIST_HEAD(, turnstile) ts_free; /* (c) Free turnstiles. */
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struct lock_object *ts_lockobj; /* (c) Lock we reference. */
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struct thread *ts_owner; /* (c + q) Who owns the lock. */
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};
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struct turnstile_chain {
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LIST_HEAD(, turnstile) tc_turnstiles; /* List of turnstiles. */
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struct mtx tc_lock; /* Spin lock for this chain. */
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};
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static struct mtx td_contested_lock;
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static struct turnstile_chain turnstile_chains[TC_TABLESIZE];
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MALLOC_DEFINE(M_TURNSTILE, "turnstiles", "turnstiles");
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/*
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* Prototypes for non-exported routines.
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*/
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static void init_turnstile0(void *dummy);
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static void propagate_priority(struct thread *);
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static void turnstile_setowner(struct turnstile *ts, struct thread *owner);
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/*
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* Walks the chain of turnstiles and their owners to propagate the priority
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* of the thread being blocked to all the threads holding locks that have to
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* release their locks before this thread can run again.
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*/
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static void
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propagate_priority(struct thread *td)
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{
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struct turnstile_chain *tc;
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struct turnstile *ts;
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struct thread *td1;
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int pri;
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mtx_assert(&sched_lock, MA_OWNED);
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pri = td->td_priority;
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ts = td->td_blocked;
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for (;;) {
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td = ts->ts_owner;
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if (td == NULL) {
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/*
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* This really isn't quite right. Really
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* ought to bump priority of thread that
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* next acquires the lock.
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*/
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return;
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}
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MPASS(td->td_proc != NULL);
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MPASS(td->td_proc->p_magic == P_MAGIC);
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/*
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* XXX: The owner of a turnstile can be stale if it is the
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* first thread to grab a slock of a sx lock. In that case
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* it is possible for us to be at SSLEEP or some other
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* weird state. We should probably just return if the state
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* isn't SRUN or SLOCK.
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*/
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KASSERT(!TD_IS_SLEEPING(td),
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("sleeping thread (pid %d) owns a non-sleepable lock",
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td->td_proc->p_pid));
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/*
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* If this thread already has higher priority than the
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* thread that is being blocked, we are finished.
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*/
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if (td->td_priority <= pri)
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return;
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/*
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* If lock holder is actually running, just bump priority.
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*/
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if (TD_IS_RUNNING(td)) {
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td->td_priority = pri;
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return;
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}
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#ifndef SMP
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/*
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* For UP, we check to see if td is curthread (this shouldn't
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* ever happen however as it would mean we are in a deadlock.)
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*/
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KASSERT(td != curthread, ("Deadlock detected"));
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#endif
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/*
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* If on run queue move to new run queue, and quit.
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* XXXKSE this gets a lot more complicated under threads
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* but try anyhow.
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*/
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if (TD_ON_RUNQ(td)) {
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MPASS(td->td_blocked == NULL);
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sched_prio(td, pri);
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return;
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}
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/*
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* Bump this thread's priority.
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*/
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td->td_priority = pri;
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/*
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* If we aren't blocked on a lock, we should be.
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*/
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KASSERT(TD_ON_LOCK(td), (
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"process %d(%s):%d holds %s but isn't blocked on a lock\n",
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td->td_proc->p_pid, td->td_proc->p_comm, td->td_state,
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ts->ts_lockobj->lo_name));
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/*
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* Pick up the lock that td is blocked on.
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*/
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ts = td->td_blocked;
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MPASS(ts != NULL);
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tc = TC_LOOKUP(ts->ts_lockobj);
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mtx_lock_spin(&tc->tc_lock);
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/*
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* This thread may not be blocked on this turnstile anymore
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* but instead might already be woken up on another CPU
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* that is waiting on sched_lock in turnstile_unpend() to
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* finish waking this thread up. We can detect this case
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* by checking to see if this thread has been given a
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* turnstile by either turnstile_signal() or
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* turnstile_wakeup(). In this case, treat the thread as
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* if it was already running.
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*/
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if (td->td_turnstile != NULL) {
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mtx_unlock_spin(&tc->tc_lock);
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return;
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}
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/*
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* Check if the thread needs to be moved up on
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* the blocked chain. It doesn't need to be moved
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* if it is already at the head of the list or if
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* the item in front of it still has a higher priority.
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*/
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if (td == TAILQ_FIRST(&ts->ts_blocked)) {
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mtx_unlock_spin(&tc->tc_lock);
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continue;
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}
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td1 = TAILQ_PREV(td, threadqueue, td_lockq);
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if (td1->td_priority <= pri) {
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mtx_unlock_spin(&tc->tc_lock);
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continue;
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}
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/*
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* Remove thread from blocked chain and determine where
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* it should be moved up to. Since we know that td1 has
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* a lower priority than td, we know that at least one
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* thread in the chain has a lower priority and that
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* td1 will thus not be NULL after the loop.
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*/
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mtx_lock_spin(&td_contested_lock);
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TAILQ_REMOVE(&ts->ts_blocked, td, td_lockq);
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TAILQ_FOREACH(td1, &ts->ts_blocked, td_lockq) {
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MPASS(td1->td_proc->p_magic == P_MAGIC);
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if (td1->td_priority > pri)
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break;
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}
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MPASS(td1 != NULL);
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TAILQ_INSERT_BEFORE(td1, td, td_lockq);
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mtx_unlock_spin(&td_contested_lock);
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CTR4(KTR_LOCK,
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"propagate_priority: td %p moved before %p on [%p] %s",
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td, td1, ts->ts_lockobj, ts->ts_lockobj->lo_name);
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mtx_unlock_spin(&tc->tc_lock);
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}
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}
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/*
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* Early initialization of turnstiles. This is not done via a SYSINIT()
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* since this needs to be initialized very early when mutexes are first
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* initialized.
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*/
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void
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init_turnstiles(void)
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{
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int i;
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for (i = 0; i < TC_TABLESIZE; i++) {
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LIST_INIT(&turnstile_chains[i].tc_turnstiles);
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mtx_init(&turnstile_chains[i].tc_lock, "turnstile chain",
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NULL, MTX_SPIN);
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}
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mtx_init(&td_contested_lock, "td_contested", NULL, MTX_SPIN);
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thread0.td_turnstile = NULL;
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}
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static void
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init_turnstile0(void *dummy)
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{
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thread0.td_turnstile = turnstile_alloc();
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}
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SYSINIT(turnstile0, SI_SUB_LOCK, SI_ORDER_ANY, init_turnstile0, NULL);
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/*
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* Set the owner of the lock this turnstile is attached to.
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*/
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static void
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turnstile_setowner(struct turnstile *ts, struct thread *owner)
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{
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mtx_assert(&td_contested_lock, MA_OWNED);
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MPASS(owner->td_proc->p_magic == P_MAGIC);
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MPASS(ts->ts_owner == NULL);
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ts->ts_owner = owner;
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LIST_INSERT_HEAD(&owner->td_contested, ts, ts_link);
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}
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/*
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* Malloc a turnstile for a new thread, initialize it and return it.
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*/
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struct turnstile *
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turnstile_alloc(void)
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{
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struct turnstile *ts;
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ts = malloc(sizeof(struct turnstile), M_TURNSTILE, M_WAITOK | M_ZERO);
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TAILQ_INIT(&ts->ts_blocked);
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TAILQ_INIT(&ts->ts_pending);
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LIST_INIT(&ts->ts_free);
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return (ts);
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}
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/*
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* Free a turnstile when a thread is destroyed.
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*/
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void
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turnstile_free(struct turnstile *ts)
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{
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MPASS(ts != NULL);
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MPASS(TAILQ_EMPTY(&ts->ts_blocked));
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MPASS(TAILQ_EMPTY(&ts->ts_pending));
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free(ts, M_TURNSTILE);
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}
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/*
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* Look up the turnstile for a lock in the hash table locking the associated
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* turnstile chain along the way. Return with the turnstile chain locked.
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* If no turnstile is found in the hash table, NULL is returned.
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*/
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struct turnstile *
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turnstile_lookup(struct lock_object *lock)
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{
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struct turnstile_chain *tc;
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struct turnstile *ts;
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tc = TC_LOOKUP(lock);
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mtx_lock_spin(&tc->tc_lock);
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LIST_FOREACH(ts, &tc->tc_turnstiles, ts_hash)
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if (ts->ts_lockobj == lock)
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return (ts);
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return (NULL);
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}
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/*
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* Unlock the turnstile chain associated with a given lock.
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*/
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void
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turnstile_release(struct lock_object *lock)
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{
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struct turnstile_chain *tc;
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tc = TC_LOOKUP(lock);
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mtx_unlock_spin(&tc->tc_lock);
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}
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/*
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* Take ownership of a turnstile and adjust the priority of the new
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* owner appropriately.
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*/
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void
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turnstile_claim(struct turnstile *ts)
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{
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struct turnstile_chain *tc;
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struct thread *td, *owner;
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tc = TC_LOOKUP(ts->ts_lockobj);
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mtx_assert(&tc->tc_lock, MA_OWNED);
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owner = curthread;
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mtx_lock_spin(&td_contested_lock);
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turnstile_setowner(ts, owner);
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mtx_unlock_spin(&td_contested_lock);
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td = TAILQ_FIRST(&ts->ts_blocked);
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MPASS(td != NULL);
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MPASS(td->td_proc->p_magic == P_MAGIC);
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mtx_unlock_spin(&tc->tc_lock);
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/*
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* Update the priority of the new owner if needed.
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*/
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mtx_lock_spin(&sched_lock);
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if (td->td_priority < owner->td_priority)
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owner->td_priority = td->td_priority;
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mtx_unlock_spin(&sched_lock);
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}
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/*
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* Block the current thread on the turnstile ts. This function will context
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* switch and not return until this thread has been woken back up. This
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* function must be called with the appropriate turnstile chain locked and
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* will return with it unlocked.
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*/
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void
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turnstile_wait(struct turnstile *ts, struct lock_object *lock,
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struct thread *owner)
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{
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struct turnstile_chain *tc;
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struct thread *td, *td1;
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td = curthread;
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tc = TC_LOOKUP(lock);
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mtx_assert(&tc->tc_lock, MA_OWNED);
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MPASS(td->td_turnstile != NULL);
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MPASS(owner != NULL);
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MPASS(owner->td_proc->p_magic == P_MAGIC);
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/* If the passed in turnstile is NULL, use this thread's turnstile. */
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if (ts == NULL) {
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ts = td->td_turnstile;
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LIST_INSERT_HEAD(&tc->tc_turnstiles, ts, ts_hash);
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KASSERT(TAILQ_EMPTY(&ts->ts_pending),
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("thread's turnstile has pending threads"));
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KASSERT(TAILQ_EMPTY(&ts->ts_blocked),
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("thread's turnstile has a non-empty queue"));
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KASSERT(LIST_EMPTY(&ts->ts_free),
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("thread's turnstile has a non-empty free list"));
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KASSERT(ts->ts_lockobj == NULL, ("stale ts_lockobj pointer"));
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ts->ts_lockobj = lock;
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mtx_lock_spin(&td_contested_lock);
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TAILQ_INSERT_TAIL(&ts->ts_blocked, td, td_lockq);
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turnstile_setowner(ts, owner);
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mtx_unlock_spin(&td_contested_lock);
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} else {
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TAILQ_FOREACH(td1, &ts->ts_blocked, td_lockq)
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if (td1->td_priority > td->td_priority)
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break;
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mtx_lock_spin(&td_contested_lock);
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if (td1 != NULL)
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TAILQ_INSERT_BEFORE(td1, td, td_lockq);
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else
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TAILQ_INSERT_TAIL(&ts->ts_blocked, td, td_lockq);
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mtx_unlock_spin(&td_contested_lock);
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MPASS(td->td_turnstile != NULL);
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LIST_INSERT_HEAD(&ts->ts_free, td->td_turnstile, ts_hash);
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MPASS(owner == ts->ts_owner);
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}
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td->td_turnstile = NULL;
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mtx_unlock_spin(&tc->tc_lock);
|
|
|
|
mtx_lock_spin(&sched_lock);
|
|
/*
|
|
* Handle race condition where a thread on another CPU that owns
|
|
* lock 'lock' could have woken us in between us dropping the
|
|
* turnstile chain lock and acquiring the sched_lock.
|
|
*/
|
|
if (td->td_flags & TDF_TSNOBLOCK) {
|
|
td->td_flags &= ~TDF_TSNOBLOCK;
|
|
mtx_unlock_spin(&sched_lock);
|
|
return;
|
|
}
|
|
|
|
#ifdef notyet
|
|
/*
|
|
* If we're borrowing an interrupted thread's VM context, we
|
|
* must clean up before going to sleep.
|
|
*/
|
|
if (td->td_ithd != NULL) {
|
|
struct ithd *it = td->td_ithd;
|
|
|
|
if (it->it_interrupted) {
|
|
if (LOCK_LOG_TEST(lock, 0))
|
|
CTR3(KTR_LOCK, "%s: %p interrupted %p",
|
|
__func__, it, it->it_interrupted);
|
|
intr_thd_fixup(it);
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/* Save who we are blocked on and switch. */
|
|
td->td_blocked = ts;
|
|
td->td_lockname = lock->lo_name;
|
|
TD_SET_LOCK(td);
|
|
propagate_priority(td);
|
|
|
|
if (LOCK_LOG_TEST(lock, 0))
|
|
CTR4(KTR_LOCK, "%s: td %p blocked on [%p] %s", __func__, td,
|
|
lock, lock->lo_name);
|
|
|
|
td->td_proc->p_stats->p_ru.ru_nvcsw++;
|
|
mi_switch();
|
|
|
|
if (LOCK_LOG_TEST(lock, 0))
|
|
CTR4(KTR_LOCK, "%s: td %p free from blocked on [%p] %s",
|
|
__func__, td, lock, lock->lo_name);
|
|
|
|
mtx_unlock_spin(&sched_lock);
|
|
}
|
|
|
|
/*
|
|
* Pick the highest priority thread on this turnstile and put it on the
|
|
* pending list. This must be called with the turnstile chain locked.
|
|
*/
|
|
int
|
|
turnstile_signal(struct turnstile *ts)
|
|
{
|
|
struct turnstile_chain *tc;
|
|
struct thread *td;
|
|
int empty;
|
|
|
|
MPASS(ts != NULL);
|
|
MPASS(curthread->td_proc->p_magic == P_MAGIC);
|
|
MPASS(ts->ts_owner == curthread);
|
|
tc = TC_LOOKUP(ts->ts_lockobj);
|
|
mtx_assert(&tc->tc_lock, MA_OWNED);
|
|
|
|
/*
|
|
* Pick the highest priority thread blocked on this lock and
|
|
* move it to the pending list.
|
|
*/
|
|
td = TAILQ_FIRST(&ts->ts_blocked);
|
|
MPASS(td->td_proc->p_magic == P_MAGIC);
|
|
mtx_lock_spin(&td_contested_lock);
|
|
TAILQ_REMOVE(&ts->ts_blocked, td, td_lockq);
|
|
mtx_unlock_spin(&td_contested_lock);
|
|
TAILQ_INSERT_TAIL(&ts->ts_pending, td, td_lockq);
|
|
|
|
/*
|
|
* If the turnstile is now empty, remove it from its chain and
|
|
* give it to the about-to-be-woken thread. Otherwise take a
|
|
* turnstile from the free list and give it to the thread.
|
|
*/
|
|
empty = TAILQ_EMPTY(&ts->ts_blocked);
|
|
if (empty)
|
|
MPASS(LIST_EMPTY(&ts->ts_free));
|
|
else
|
|
ts = LIST_FIRST(&ts->ts_free);
|
|
MPASS(ts != NULL);
|
|
LIST_REMOVE(ts, ts_hash);
|
|
td->td_turnstile = ts;
|
|
|
|
return (empty);
|
|
}
|
|
|
|
/*
|
|
* Put all blocked threads on the pending list. This must be called with
|
|
* the turnstile chain locked.
|
|
*/
|
|
void
|
|
turnstile_wakeup(struct turnstile *ts)
|
|
{
|
|
struct turnstile_chain *tc;
|
|
struct turnstile *ts1;
|
|
struct thread *td;
|
|
|
|
MPASS(ts != NULL);
|
|
MPASS(curthread->td_proc->p_magic == P_MAGIC);
|
|
MPASS(ts->ts_owner == curthread);
|
|
tc = TC_LOOKUP(ts->ts_lockobj);
|
|
mtx_assert(&tc->tc_lock, MA_OWNED);
|
|
|
|
/*
|
|
* Transfer the blocked list to the pending list.
|
|
*/
|
|
mtx_lock_spin(&td_contested_lock);
|
|
TAILQ_CONCAT(&ts->ts_pending, &ts->ts_blocked, td_lockq);
|
|
mtx_unlock_spin(&td_contested_lock);
|
|
|
|
/*
|
|
* Give a turnstile to each thread. The last thread gets
|
|
* this turnstile.
|
|
*/
|
|
TAILQ_FOREACH(td, &ts->ts_pending, td_lockq) {
|
|
if (LIST_EMPTY(&ts->ts_free)) {
|
|
MPASS(TAILQ_NEXT(td, td_lockq) == NULL);
|
|
ts1 = ts;
|
|
} else
|
|
ts1 = LIST_FIRST(&ts->ts_free);
|
|
MPASS(ts1 != NULL);
|
|
LIST_REMOVE(ts1, ts_hash);
|
|
td->td_turnstile = ts1;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Wakeup all threads on the pending list and adjust the priority of the
|
|
* current thread appropriately. This must be called with the turnstile
|
|
* chain locked.
|
|
*/
|
|
void
|
|
turnstile_unpend(struct turnstile *ts)
|
|
{
|
|
TAILQ_HEAD( ,thread) pending_threads;
|
|
struct turnstile_chain *tc;
|
|
struct thread *td;
|
|
int cp, pri;
|
|
|
|
MPASS(ts != NULL);
|
|
MPASS(ts->ts_owner == curthread);
|
|
tc = TC_LOOKUP(ts->ts_lockobj);
|
|
mtx_assert(&tc->tc_lock, MA_OWNED);
|
|
MPASS(!TAILQ_EMPTY(&ts->ts_pending));
|
|
|
|
/*
|
|
* Move the list of pending threads out of the turnstile and
|
|
* into a local variable.
|
|
*/
|
|
TAILQ_INIT(&pending_threads);
|
|
TAILQ_CONCAT(&pending_threads, &ts->ts_pending, td_lockq);
|
|
#ifdef INVARIANTS
|
|
if (TAILQ_EMPTY(&ts->ts_blocked))
|
|
ts->ts_lockobj = NULL;
|
|
#endif
|
|
|
|
/*
|
|
* Remove the turnstile from this thread's list of contested locks
|
|
* since this thread doesn't own it anymore. New threads will
|
|
* not be blocking on the turnstile until it is claimed by a new
|
|
* owner.
|
|
*/
|
|
mtx_lock_spin(&td_contested_lock);
|
|
ts->ts_owner = NULL;
|
|
LIST_REMOVE(ts, ts_link);
|
|
mtx_unlock_spin(&td_contested_lock);
|
|
mtx_unlock_spin(&tc->tc_lock);
|
|
|
|
/*
|
|
* Adjust the priority of curthread based on other contested
|
|
* locks it owns. Don't lower the priority below the base
|
|
* priority however.
|
|
*/
|
|
td = curthread;
|
|
pri = PRI_MAX;
|
|
mtx_lock_spin(&sched_lock);
|
|
mtx_lock_spin(&td_contested_lock);
|
|
LIST_FOREACH(ts, &td->td_contested, ts_link) {
|
|
cp = TAILQ_FIRST(&ts->ts_blocked)->td_priority;
|
|
if (cp < pri)
|
|
pri = cp;
|
|
}
|
|
mtx_unlock_spin(&td_contested_lock);
|
|
if (pri > td->td_base_pri)
|
|
pri = td->td_base_pri;
|
|
td->td_priority = pri;
|
|
|
|
/*
|
|
* Wake up all the pending threads. If a thread is not blocked
|
|
* on a lock, then it is currently executing on another CPU in
|
|
* turnstile_wait() or sitting on a run queue waiting to resume
|
|
* in turnstile_wait(). Set a flag to force it to try to acquire
|
|
* the lock again instead of blocking.
|
|
*/
|
|
while (!TAILQ_EMPTY(&pending_threads)) {
|
|
td = TAILQ_FIRST(&pending_threads);
|
|
TAILQ_REMOVE(&pending_threads, td, td_lockq);
|
|
MPASS(td->td_proc->p_magic == P_MAGIC);
|
|
if (TD_ON_LOCK(td)) {
|
|
td->td_blocked = NULL;
|
|
td->td_lockname = NULL;
|
|
TD_CLR_LOCK(td);
|
|
MPASS(TD_CAN_RUN(td));
|
|
setrunqueue(td);
|
|
} else {
|
|
td->td_flags |= TDF_TSNOBLOCK;
|
|
MPASS(TD_IS_RUNNING(td) || TD_ON_RUNQ(td));
|
|
}
|
|
}
|
|
mtx_unlock_spin(&sched_lock);
|
|
}
|
|
|
|
/*
|
|
* Return the first thread in a turnstile.
|
|
*/
|
|
struct thread *
|
|
turnstile_head(struct turnstile *ts)
|
|
{
|
|
#ifdef INVARIANTS
|
|
struct turnstile_chain *tc;
|
|
|
|
MPASS(ts != NULL);
|
|
tc = TC_LOOKUP(ts->ts_lockobj);
|
|
mtx_assert(&tc->tc_lock, MA_OWNED);
|
|
#endif
|
|
return (TAILQ_FIRST(&ts->ts_blocked));
|
|
}
|
|
|
|
/*
|
|
* Returns true if a turnstile is empty.
|
|
*/
|
|
int
|
|
turnstile_empty(struct turnstile *ts)
|
|
{
|
|
#ifdef INVARIANTS
|
|
struct turnstile_chain *tc;
|
|
|
|
MPASS(ts != NULL);
|
|
tc = TC_LOOKUP(ts->ts_lockobj);
|
|
mtx_assert(&tc->tc_lock, MA_OWNED);
|
|
#endif
|
|
return (TAILQ_EMPTY(&ts->ts_blocked));
|
|
}
|