/* $NetBSD: trampoline_p.h,v 1.1.2.2 2024/02/24 13:07:22 martin Exp $ */ /* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * SPDX-License-Identifier: MPL-2.0 * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, you can obtain one at https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ #pragma once #include /*! \file isc/trampoline_p.h * \brief isc__trampoline: allows safe reuse of thread ID numbers. * * The 'isc_hp' hazard pointer API uses an internal thread ID * variable ('tid_v') that is incremented for each new thread that uses * hazard pointers. This thread ID is then used as an index into a global * shared table of hazard pointer state. * * Since the thread ID is only incremented and never decremented, the * table can overflow if threads are frequently created and destroyed. * * A trampoline is a thin wrapper around any function to be called from * a newly launched thread. It maintains a table of thread IDs used by * current and previous threads; when a thread is destroyed, its slot in * the trampoline table becomes available, and the next thread to occupy * that slot can use the same thread ID that its predecessor did. * * The trampoline table initially has space for 64 worker threads in * addition to the main thread. If more threads than that are in * concurrent use, the table is reallocated with twice as much space. * (Note that the number of concurrent threads is currently capped at * 128 by the queue and hazard pointer implementations.) */ typedef struct isc__trampoline isc__trampoline_t; void isc__trampoline_initialize(void); /*%< * Initialize the thread trampoline internal structures, must be called only * once as a library constructor (see lib/isc/lib.c). */ void isc__trampoline_shutdown(void); /*%< * Destroy the thread trampoline internal structures, must be called only * once as a library destructor (see lib/isc/lib.c). */ isc__trampoline_t * isc__trampoline_get(isc_threadfunc_t start_routine, isc_threadarg_t arg); /*%< * Get a free thread trampoline structure and initialize it with * start_routine and arg passed to start_routine. * * Requires: *\li 'start_routine' is a valid non-NULL thread start_routine */ void isc__trampoline_attach(isc__trampoline_t *trampoline); void isc__trampoline_detach(isc__trampoline_t *trampoline); /*%< * Attach/detach the trampoline to/from the current thread. * * Requires: * \li 'trampoline' is a valid isc__trampoline_t */ isc_threadresult_t isc__trampoline_run(isc_threadarg_t arg); /*%< * Run the thread trampoline, this will get passed to the actual * pthread_create() (or Windows equivalent), initialize the isc_tid_v. * * Requires: *\li 'arg' is a valid isc_trampoline_t * * Returns: *\li return value from start_routine (see isc__trampoline_get()) */