semmutex-linux.cpp@ 19167

Last change on this file since 19167 was 8651, checked in by vboxsync, 17 years ago
Moved the strictness indicators into internal/strict.h.
Property svn:eol-style set to `native` Property svn:keywords set to `Id`
File size: 8.9 KB

Line
1	/* $Id: semmutex-linux.cpp 8651 2008-05-07 12:16:29Z vboxsync $ */
2	/** @file
3	* IPRT - Mutex Semaphore, Linux (2.6.x+).
4	*/
5
6	/*
7	* Copyright (C) 2006-2007 Sun Microsystems, Inc.
8	*
9	* This file is part of VirtualBox Open Source Edition (OSE), as
10	* available from http://www.virtualbox.org. This file is free software;
11	* you can redistribute it and/or modify it under the terms of the GNU
12	* General Public License (GPL) as published by the Free Software
13	* Foundation, in version 2 as it comes in the "COPYING" file of the
14	* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
15	* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
16	*
17	* The contents of this file may alternatively be used under the terms
18	* of the Common Development and Distribution License Version 1.0
19	* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
20	* VirtualBox OSE distribution, in which case the provisions of the
21	* CDDL are applicable instead of those of the GPL.
22	*
23	* You may elect to license modified versions of this file under the
24	* terms and conditions of either the GPL or the CDDL or both.
25	*
26	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
27	* Clara, CA 95054 USA or visit http://www.sun.com if you need
28	* additional information or have any questions.
29	*/
30
31	/*******************************************************************************
32	* Header Files *
33	*******************************************************************************/
34	#include <iprt/semaphore.h>
35	#include <iprt/assert.h>
36	#include <iprt/alloc.h>
37	#include <iprt/thread.h>
38	#include <iprt/asm.h>
39	#include <iprt/err.h>
40	#include "internal/magics.h"
41	#include "internal/strict.h"
42
43	#include <errno.h>
44	#include <limits.h>
45	#include <pthread.h>
46	#include <unistd.h>
47	#include <sys/time.h>
48	#include <sys/syscall.h>
49	#if 0 /* With 2.6.17 futex.h has become C++ unfriendly. */
50	# include <linux/futex.h>
51	#else
52	# define FUTEX_WAIT 0
53	# define FUTEX_WAKE 1
54	#endif
55
56
57	/*******************************************************************************
58	* Structures and Typedefs *
59	*******************************************************************************/
60	/**
61	* Linux internal representation of a Mutex semaphore.
62	*/
63	struct RTSEMMUTEXINTERNAL
64	{
65	/** The futex state variable.
66	* 0 means unlocked.
67	* 1 means locked, no waiters.
68	* 2 means locked, one or more waiters.
69	*/
70	int32_t volatile iState;
71	/** Nesting count. */
72	uint32_t volatile cNesting;
73	/** The owner of the mutex. */
74	pthread_t volatile Owner;
75	/** Magic value. */
76	intptr_t volatile iMagic;
77	};
78
79
80	/**
81	* Wrapper for the futex syscall.
82	*/
83	static long sys_futex(int32_t volatile uaddr, int op, int val, struct timespec utime, int32_t *uaddr2, int val3)
84	{
85	errno = 0;
86	long rc = syscall(__NR_futex, uaddr, op, val, utime, uaddr2, val3);
87	if (rc < 0)
88	{
89	Assert(rc == -1);
90	rc = -errno;
91	}
92	return rc;
93	}
94
95
96	RTDECL(int) RTSemMutexCreate(PRTSEMMUTEX pMutexSem)
97	{
98	/*
99	* Allocate semaphore handle.
100	*/
101	struct RTSEMMUTEXINTERNAL pThis = (struct RTSEMMUTEXINTERNAL )RTMemAlloc(sizeof(struct RTSEMMUTEXINTERNAL));
102	if (pThis)
103	{
104	pThis->iMagic = RTSEMMUTEX_MAGIC;
105	pThis->iState = 0;
106	pThis->Owner = (pthread_t)~0;
107	pThis->cNesting = 0;
108
109	*pMutexSem = pThis;
110	return VINF_SUCCESS;
111	}
112
113	return VERR_NO_MEMORY;
114	}
115
116
117	RTDECL(int) RTSemMutexDestroy(RTSEMMUTEX MutexSem)
118	{
119	/*
120	* Validate input.
121	*/
122	if (MutexSem == NIL_RTSEMMUTEX)
123	return VERR_INVALID_HANDLE;
124	struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
125	AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
126	AssertMsgReturn(pThis->iMagic == RTSEMMUTEX_MAGIC,
127	("MutexSem=%p iMagic=%#x\n", pThis, pThis->iMagic),
128	VERR_INVALID_HANDLE);
129
130	/*
131	* Invalidate the semaphore and wake up anyone waiting on it.
132	*/
133	ASMAtomicXchgSize(&pThis->iMagic, RTSEMMUTEX_MAGIC + 1);
134	if (ASMAtomicXchgS32(&pThis->iState, 0) > 0)
135	{
136	sys_futex(&pThis->iState, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
137	usleep(1000);
138	}
139	pThis->Owner = (pthread_t)~0;
140	pThis->cNesting = 0;
141
142	/*
143	* Free the semaphore memory and be gone.
144	*/
145	RTMemFree(pThis);
146	return VINF_SUCCESS;
147	}
148
149
150	static int rtsemMutexRequest(RTSEMMUTEX MutexSem, unsigned cMillies, bool fAutoResume)
151	{
152	/*
153	* Validate input.
154	*/
155	struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
156	AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMMUTEX_MAGIC,
157	VERR_INVALID_HANDLE);
158
159	/*
160	* Check if nested request.
161	*/
162	pthread_t Self = pthread_self();
163	if ( pThis->Owner == Self
164	&& pThis->cNesting > 0)
165	{
166	pThis->cNesting++;
167	return VINF_SUCCESS;
168	}
169
170	/*
171	* Convert timeout value.
172	*/
173	struct timespec ts;
174	struct timespec *pTimeout = NULL;
175	if (cMillies != RT_INDEFINITE_WAIT)
176	{
177	ts.tv_sec = cMillies / 1000;
178	ts.tv_nsec = (cMillies % 1000) * 1000000;
179	pTimeout = &ts;
180	}
181
182	/*
183	* Lock the mutex.
184	* Optimize for the uncontended case (makes 1-2 ns difference).
185	*/
186	if (RT_UNLIKELY(!ASMAtomicCmpXchgS32(&pThis->iState, 1, 0)))
187	{
188	for (;;)
189	{
190	int32_t iOld = ASMAtomicXchgS32(&pThis->iState, 2);
191
192	/*
193	* Was the lock released in the meantime? This is unlikely (but possible)
194	*/
195	if (RT_UNLIKELY(iOld == 0))
196	break;
197
198	/*
199	* Go to sleep.
200	*/
201	long rc = sys_futex(&pThis->iState, FUTEX_WAIT, 2, pTimeout, NULL, 0);
202	if (RT_UNLIKELY(pThis->iMagic != RTSEMMUTEX_MAGIC))
203	return VERR_SEM_DESTROYED;
204
205	/*
206	* Act on the wakup code.
207	*/
208	if (rc == -ETIMEDOUT)
209	{
210	Assert(pTimeout);
211	return VERR_TIMEOUT;
212	}
213	if (rc == 0)
214	/* we'll leave the loop now unless another thread is faster */;
215	else if (rc == -EWOULDBLOCK)
216	/* retry with new value. */;
217	else if (rc == -EINTR)
218	{
219	if (!fAutoResume)
220	return VERR_INTERRUPTED;
221	}
222	else
223	{
224	/* this shouldn't happen! */
225	AssertMsgFailed(("rc=%ld errno=%d\n", rc, errno));
226	return RTErrConvertFromErrno(rc);
227	}
228	}
229
230	/*
231	* When leaving this loop, iState is set to 2. This means that we gained the
232	* lock and there are _possibly_ some waiters. We don't know exactly as another
233	* thread might entered this loop at nearly the same time. Therefore we will
234	* call futex_wakeup once too often (if _no_ other thread entered this loop).
235	* The key problem is the simple futex_wait test for x != y (iState != 2) in
236	* our case).
237	*/
238	}
239
240	/*
241	* Set the owner and nesting.
242	*/
243	pThis->Owner = Self;
244	ASMAtomicXchgU32(&pThis->cNesting, 1);
245	#ifdef RTSEMMUTEX_STRICT
246	RTTHREAD Thread = RTThreadSelf();
247	if (Thread != NIL_RTTHREAD)
248	RTThreadWriteLockInc(Thread);
249	#endif
250	return VINF_SUCCESS;
251	}
252
253
254	RTDECL(int) RTSemMutexRequest(RTSEMMUTEX MutexSem, unsigned cMillies)
255	{
256	int rc = rtsemMutexRequest(MutexSem, cMillies, true);
257	Assert(rc != VERR_INTERRUPTED);
258	return rc;
259	}
260
261
262	RTDECL(int) RTSemMutexRequestNoResume(RTSEMMUTEX MutexSem, unsigned cMillies)
263	{
264	return rtsemMutexRequest(MutexSem, cMillies, false);
265	}
266
267
268	RTDECL(int) RTSemMutexRelease(RTSEMMUTEX MutexSem)
269	{
270	/*
271	* Validate input.
272	*/
273	struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
274	AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMMUTEX_MAGIC,
275	VERR_INVALID_HANDLE);
276
277	/*
278	* Check if nested.
279	*/
280	pthread_t Self = pthread_self();
281	if (RT_UNLIKELY( pThis->Owner != Self
282	\|\| pThis->cNesting == 0))
283	{
284	AssertMsgFailed(("Not owner of mutex %p!! Self=%08x Owner=%08x cNesting=%d\n",
285	pThis, Self, pThis->Owner, pThis->cNesting));
286	return VERR_NOT_OWNER;
287	}
288
289	/*
290	* If nested we'll just pop a nesting.
291	*/
292	if (pThis->cNesting > 1)
293	{
294	pThis->cNesting--;
295	return VINF_SUCCESS;
296	}
297
298	/*
299	* Clear the state. (cNesting == 1)
300	*/
301	#ifdef RTSEMMUTEX_STRICT
302	RTTHREAD Thread = RTThreadSelf();
303	if (Thread != NIL_RTTHREAD)
304	RTThreadWriteLockDec(Thread);
305	#endif
306	pThis->Owner = (pthread_t)~0;
307	ASMAtomicXchgU32(&pThis->cNesting, 0);
308
309	/*
310	* Release the mutex.
311	*/
312	int32_t iNew = ASMAtomicDecS32(&pThis->iState);
313	if (RT_UNLIKELY(iNew != 0))
314	{
315	/* somebody is waiting, try wake up one of them. */
316	ASMAtomicXchgS32(&pThis->iState, 0);
317	(void)sys_futex(&pThis->iState, FUTEX_WAKE, 1, NULL, NULL, 0);
318	}
319	return VINF_SUCCESS;
320	}
321

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source: vbox/trunk/src/VBox/Runtime/r3/linux/semmutex-linux.cpp@ 19167

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