/* $NetBSD: pthread_switch.S,v 1.5 2003/09/07 14:47:47 cl Exp $ */ /*- * Copyright (c) 2001 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Nathan J. Williams. * * 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 \ call_pal PAL_bugchk ; \ /* 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,tmp) \ ldq tmp, PT_TRAPUC(pt) ; \ bne tmp, 1f ; \ ldq tmp, PT_UC(pt) ; \ 1: lda sp, -STACKSPACE(tmp) ; \ stq zero, PT_TRAPUC(pt) NESTED(pthread__switch, 2, CONTEXTSIZE + 24, ra, 0, 0) LDGP(pv) lda sp, -(CONTEXTSIZE + 24)(sp) stq ra, 0(sp) stq a0, 8(sp) stq a1, 16(sp) /* Get the current context */ lda a0, 24(sp) CALL(_getcontext_u) ldq a0, 8(sp) ldq a1, 16(sp) /* Edit the context to make it continue below, rather than here */ lda t3, 24(sp) lda t1, pthread__switch_return_point stq t1, (UC_GREGS + _REG_PC * 8)(t3) lda t0, 24(sp) stq t0, PT_UC(a0) STACK_SWITCH(a1, t2) mov t2, a0 CALL(_setcontext_u) XNESTED(pthread__switch_return_point, 2) ldq ra, 0(sp) lda sp, (CONTEXTSIZE + 24)(sp) RET END(pthread__switch) /* * Helper switch code used by pthread__locked_switch() and * pthread__upcall_switch() when they discover spinlock preemption. */ NESTED(pthread__switch_away, 3, 0, ra, 0, 0) STACK_SWITCH(a1, s2) /* 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 a2 to * let us know, and we decrement it now that we're no longer * using the old stack. */ beq a2, 1f ldl t0, PT_SPINLOCKS(a0) subl t0, 1, t0 stl t0, PT_SPINLOCKS(a0) 1: mov s2, a0 CALL(_setcontext_u) NOTREACHED END(pthread__switch_away) NESTED(pthread__locked_switch, 3, CONTEXTSIZE + 32, ra, 0x00030000, 0) LDGP(pv) lda sp, -(CONTEXTSIZE + 32)(sp) stq ra, 0(sp) stq a0, 8(sp) stq a1, 16(sp) stq a2, 24(sp) /* Make sure we get continuted */ ldl t0, PT_SPINLOCKS(a1) addl t0, 1, t0 stl t0, PT_SPINLOCKS(a1) /* Get the current context */ lda a0, 32(sp) CALL(_getcontext_u) ldq a0, 8(sp) ldq a1, 16(sp) ldq a2, 24(sp) /* Edit the context to make it continue below, rather than here */ lda t3, 32(sp) lda t1, locked_return_point stq t1, (UC_GREGS + _REG_PC * 8)(t3) lda t0, 32(sp) stq t0, PT_UC(a0) STACK_SWITCH(a1, t2) /* Check if the switcher was preempted and continued to here. */ ldq t0, PT_NEXT(a0) beq t0, 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. */ stq a2, PT_HELDLOCK(a0) stq t2, PT_SWITCHTOUC(a0) stq a1, PT_SWITCHTO(a0) ldl t4, PT_SPINLOCKS(a0) subl t4, 1, t4 stl t4, PT_SPINLOCKS(a0) mov a1, a0 mov t0, a1 mov 1, a2 jmp zero, pthread__switch_away NOTREACHED /* 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... */ ldl t0, PT_SPINLOCKS(a0) subl t0, 1, t0 stl t0, PT_SPINLOCKS(a0) /* ... actually release the lock.. */ mb stl zero, 0(a2) /* .. and remove the fake lock */ ldl t0, PT_SPINLOCKS(a1) subl t0, 1, t0 stl t0, PT_SPINLOCKS(a1) /* Check if we were preempted while holding the fake lock. */ ldq t0, PT_NEXT(a1) beq t0, 2f /* Yes, we were. Go to the next element in the chain. */ stq t2, PT_SWITCHTOUC(a1) stq a1, PT_SWITCHTO(a1) mov a1, a0 mov t0, a1 mov zero, a2 jmp zero, pthread__switch_away NOTREACHED 2: mov t2, a0 CALL(_setcontext_u) locked_return_point: ldq ra, 0(sp) lda sp, (CONTEXTSIZE + 32)(sp) RET END(pthread__locked_switch) /* * void pthread__upcall_switch(pthread_t self, pthread_t next); * * Quit an upcall, recycle it, and jump to the selected thread. */ NESTED(pthread__upcall_switch,2,0,ra,0,0) LDGP(pv) /* Loading the global pointer is unnecessary; this routine * is only ever called from the pthreads module, and the C * code will have gp set up. * * Also, 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 */ ldl t0, PT_SPINLOCKS(a1) addl t0, 1, t0 stl t0, PT_SPINLOCKS(a1) STACK_SWITCH(a1,s2) /* Check if the upcall code was preempted and continued to here. */ ldq t0, PT_NEXT(a0) beq t0, 1f /* Yes, it was. Stash the thread we were going to switch to, * and switch to the next thread in the continuation chain. */ stq s2, PT_SWITCHTOUC(a0) stq a1, PT_SWITCHTO(a0) mov a1, a0 mov t0, a1 mov 1, a2 jmp zero, pthread__switch_away NOTREACHED /* No old-upcall-preemption */ 1: mov a0, s0 mov a1, s1 CALL(pthread__sa_recycle) mov s0, a0 mov s1, a1 /* We can now release the fake lock. */ ldl t0, PT_SPINLOCKS(a1) subl t0, 1, t0 stl t0, PT_SPINLOCKS(a1) /* Check if we were preempted and continued while faking the lock */ ldq t0, PT_NEXT(a1) beq t0, 2f /* Yes, we were. Stash the to-be-switched-to context in our thread * structure and go to the next link in the chain. */ stq s2, PT_SWITCHTOUC(a1) stq a1, PT_SWITCHTO(a1) mov a1, a0 mov t0, a1 mov 0, a2 jmp zero, pthread__switch_away /* No new-upcall-preemption */ 2: mov s2, a0 CALL(_setcontext_u) NOTREACHED END(pthread__upcall_switch)