/* $NetBSD: pthread_switch.S,v 1.5 2003/09/07 14:47:56 cl Exp $ */ /*- * Copyright (c) 2001, 2003 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Nathan J. Williams and Matt Thomas. * * 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * This file implements low-level routines that are exported to * the machine-independent parts of the thread library. The routines are: * * void pthread__switch(pthread_t self, pthread_t next); * void pthread__upcall_switch(pthread_t self, pthread_t next); * void pthread__locked_switch(pthread_t self, pthread_t next, * pt_spin_t *lock); * * as well as some utility code used by these routines. */ #include #include "assym.h" /* Force an error when "notreached" code is reached. */ #define NOTREACHED \ halt; \ /* NOTREACHED */ /* *** WARNING *** * STACK_SWITCH is more subtle than it looks. Please go read the extended * comment in the i386 pthread_switch.S file. */ #define STACK_SWITCH(pt) \ movl PT_TRAPUC(pt),%sp ; \ bneq 1f; \ movl PT_UC(pt),%sp; \ 1: clrl PT_TRAPUC(pt) ENTRY(pthread__switch, 0) movab -(CONTEXTSIZE)(%sp), %sp /* Get the current context */ pushl %sp calls $1,_getcontext_u /* Edit the context to make it continue below, rather than here */ movab switch_return_point,(UC_GREGS + _REG_PC)(%sp) movq 4(%ap),%r2 movl %sp,PT_UC(%r2) /* self->pt_uc = &context */ STACK_SWITCH(%r3) /* r2 = self; r3 = next */ pthread__switch_return_point: .globl pthread__switch_return_point setcontext: pushl %sp /* sp = &context */ calls $1,_setcontext_u NOTREACHED switch_return_point: ret /* * Helper switch code used by pthread__locked_switch() and * pthread__upcall_switch() when they discover spinlock preemption. */ pthread__switch_away: STACK_SWITCH(%r3) /* If we're invoked from the switch-to-next provisions of * pthread__locked_switch or pthread__upcall_switch, there may * be a fake spinlock-count set. If so, they will set r4 to * let us know, and we decrement it now that we're no longer * using the old stack. */ subl2 %r4,PT_SPINLOCKS(%r5) jbr setcontext /* sp = &context */ /* * void pthread__locked_switch(pthread_t self, pthread_t next, * pt_spin_t *lock); */ ENTRY(pthread__locked_switch, 0) movab -(CONTEXTSIZE)(%sp),%sp movl 8(%ap),%r5 /* Make sure we get continuted */ incl PT_SPINLOCKS(%r5) /* Get the current context */ pushl %sp calls $1, _getcontext_u movq 4(%ap),%r4 /* Edit the context to make it continue below, rather than here */ movab locked_return_point, (UC_GREGS + _REG_PC)(%sp) movl %sp, PT_UC(%r4) STACK_SWITCH(%r5) /* sp = next->pt_uc */ /* Check if the switcher was preempted and continued to here. */ movl PT_NEXT(%r4),%r3 beql 1f /* Yes, it was. Stash the thread we were going to switch to, * the lock the original thread was holding, * and switch to the next thread in the continuation chain. * Mark the fact that this was a locked switch, and so the * thread does not need to be put on a run queue. * Don't release the lock. It's possible that if we do so, * PT_SWITCHTO will be stomped by another switch_lock and * preemption. */ movl 12(%ap), PT_HELDLOCK(%r4) movl %sp, PT_SWITCHTOUC(%r4) movl %r5, PT_SWITCHTO(%r4) incl PT_SPINLOCKS(%r4) /* %r3 = self->pt_next */ movl $1, %r4 brw pthread__switch_away /* No locked old-preemption */ 1: /* We've moved to the new stack, and the old context has been * saved. The queue lock can be released. */ /* Reduce the lock count... */ decl PT_SPINLOCKS(%r4) /* ... actually release the lock.. */ clrl *12(%ap) /* .. and remove the fake lock */ incl PT_SPINLOCKS(%r5) /* Check if we were preempted while holding the fake lock. */ movl PT_NEXT(%r5),%r3 jeql setcontext /* Yes, we were. Go to the next element in the chain. */ movl %sp, PT_SWITCHTOUC(%r5) movl %r5, PT_SWITCHTO(%r5) clrl %r4 brw pthread__switch_away NOTREACHED locked_return_point: ret /* * void pthread__upcall_switch(pthread_t self, pthread_t next); * * Quit an upcall, recycle it, and jump to the selected thread. */ ENTRY(pthread__upcall_switch, 0) movq 4(%ap),%r4 /* * this code never returns, so we can treat s0-s6 as * convenient registers that will be saved for us by callees, * but that we do not have to save. */ /* Create a "fake" lock count so that this code will be continued */ incl PT_SPINLOCKS(%r4) STACK_SWITCH(%r5) /* Check if the upcall code was preempted and continued to here. */ movl PT_NEXT(%r4),%r3 beql 1f /* Yes, it was. Stash the thread we were going to switch to, * and switch to the next thread in the continuation chain. */ movl %sp, PT_SWITCHTOUC(%r4) movq %r5,PT_SWITCHTO(%r4) movl $1,%r4 brw pthread__switch_away /* No old-upcall-preemption */ 1: movq %r4,-(%sp) calls $2, pthread__sa_recycle /* grab the arguments again */ movq 4(%ap),%r4 /* We can now release the fake lock. */ decl PT_SPINLOCKS(%r5) /* Check if we were preempted and continued while faking the lock */ movl PT_NEXT(%r5),%r3 jeql setcontext /* No new-upcall-preemption */ /* Yes, we were. Stash the to-be-switched-to context in our thread * structure and go to the next link in the chain. */ movl %sp, PT_SWITCHTOUC(%r5) movl %r5, PT_SWITCHTO(%r5) clrl %r4 brw pthread__switch_away