1 /* 2 * Copyright (c) 2011 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 /* 35 * Implement helper routines for the refcount inlines in sys/refcount.h. 36 * 37 * These helpers implement the refcount_release_wakeup() and refcount_wait() 38 * APIs for the non-trivial or race case. The trivial non-race case is 39 * handled by the inline in sys/refcount.h 40 */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/thread.h> 47 #include <sys/refcount.h> 48 49 #include <machine/cpufunc.h> 50 51 /* 52 * Interlocked wait against a decrement-to-0 (sans the REFCNTF_WAITING flag). 53 * 54 * Users of this waiting API must use refcount_release_wakeup() to release 55 * refs instead of refcount_release(). refcount_release() will not wake 56 * up waiters. 57 */ 58 void 59 _refcount_wait(volatile u_int *countp, const char *wstr) 60 { 61 u_int n; 62 int base_ticks = ticks; 63 64 n = *countp; 65 for (;;) { 66 cpu_ccfence(); 67 if ((n & ~REFCNTF_WAITING) == 0) 68 break; 69 if ((int)(ticks - base_ticks) >= hz*60 - 1) { 70 kprintf("warning: refcount_wait %s: long wait\n", wstr); 71 base_ticks = ticks; 72 } 73 tsleep_interlock(countp, 0); 74 if (atomic_fcmpset_int(countp, &n, n | REFCNTF_WAITING)) 75 tsleep(countp, PINTERLOCKED, wstr, hz*10); 76 } 77 } 78