98c926b20f
callout is first initialised, using a new function callout_init_mtx(). The callout system will acquire this mutex before calling the callout function and release it on return. In addition, the callout system uses the mutex to avoid most of the complications and race conditions inherent in asynchronous timer facilities, so mutex-protected callouts have much simpler semantics. As long as the mutex is held when invoking callout_stop() or callout_reset(), then these functions will guarantee that the callout will be stopped, even if softclock() had already begun to process the callout. Existing Giant-locked callouts will automatically pick up the new race-free semantics. This should close a number of race conditions in the USB code and probably other areas of the kernel too. There should be no change in behaviour for "MP-safe" callouts; these still need to use the techniques mentioned in timeout(9) to avoid race conditions.
91 lines
3.5 KiB
C
91 lines
3.5 KiB
C
/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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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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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS OR CONTRIBUTORS 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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* @(#)callout.h 8.2 (Berkeley) 1/21/94
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* $FreeBSD$
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*/
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#ifndef _SYS_CALLOUT_H_
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#define _SYS_CALLOUT_H_
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#include <sys/queue.h>
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struct mtx;
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SLIST_HEAD(callout_list, callout);
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TAILQ_HEAD(callout_tailq, callout);
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struct callout {
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union {
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SLIST_ENTRY(callout) sle;
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TAILQ_ENTRY(callout) tqe;
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} c_links;
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int c_time; /* ticks to the event */
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void *c_arg; /* function argument */
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void (*c_func)(void *); /* function to call */
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struct mtx *c_mtx; /* mutex to lock */
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int c_flags; /* state of this entry */
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};
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#define CALLOUT_LOCAL_ALLOC 0x0001 /* was allocated from callfree */
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#define CALLOUT_ACTIVE 0x0002 /* callout is currently active */
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#define CALLOUT_PENDING 0x0004 /* callout is waiting for timeout */
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#define CALLOUT_MPSAFE 0x0008 /* callout handler is mp safe */
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#define CALLOUT_RETURNUNLOCKED 0x0010 /* handler returns with mtx unlocked */
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struct callout_handle {
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struct callout *callout;
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};
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#ifdef _KERNEL
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extern struct callout_list callfree;
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extern struct callout *callout;
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extern int ncallout;
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extern struct callout_tailq *callwheel;
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extern int callwheelsize, callwheelbits, callwheelmask, softticks;
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extern struct mtx callout_lock;
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#define callout_active(c) ((c)->c_flags & CALLOUT_ACTIVE)
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#define callout_deactivate(c) ((c)->c_flags &= ~CALLOUT_ACTIVE)
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#define callout_drain(c) _callout_stop_safe(c, 1)
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void callout_init(struct callout *, int);
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void callout_init_mtx(struct callout *, struct mtx *, int);
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#define callout_pending(c) ((c)->c_flags & CALLOUT_PENDING)
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void callout_reset(struct callout *, int, void (*)(void *), void *);
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#define callout_stop(c) _callout_stop_safe(c, 0)
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int _callout_stop_safe(struct callout *, int);
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#endif
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#endif /* _SYS_CALLOUT_H_ */
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