1 // Copyright (c) 2005, 2006, Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 // * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 // * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
14 // * Neither the name of Google Inc. nor the names of its
15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30 // ---
31 // Author: Sanjay Ghemawat <opensource@google.com>
32
33 #ifndef TCMALLOC_INTERNAL_SPINLOCK_H__
34 #define TCMALLOC_INTERNAL_SPINLOCK_H__
35
36 #if (CPU(X86) || CPU(X86_64) || CPU(PPC)) && (COMPILER(GCC) || COMPILER(MSVC))
37
38 #include <time.h> /* For nanosleep() */
39
40 #include <sched.h> /* For sched_yield() */
41
42 #if HAVE(STDINT_H)
43 #include <stdint.h>
44 #elif HAVE(INTTYPES_H)
45 #include <inttypes.h>
46 #else
47 #include <sys/types.h>
48 #endif
49
50 #if OS(WINDOWS)
51 #ifndef WIN32_LEAN_AND_MEAN
52 #define WIN32_LEAN_AND_MEAN
53 #endif
54 #include <windows.h>
55 #endif
56
57 static void TCMalloc_SlowLock(volatile unsigned int* lockword);
58
59 // The following is a struct so that it can be initialized at compile time
60 struct TCMalloc_SpinLock {
61
LockTCMalloc_SpinLock62 inline void Lock() {
63 int r;
64 #if COMPILER(GCC)
65 #if CPU(X86) || CPU(X86_64)
66 __asm__ __volatile__
67 ("xchgl %0, %1"
68 : "=r"(r), "=m"(lockword_)
69 : "0"(1), "m"(lockword_)
70 : "memory");
71 #else
72 volatile unsigned int *lockword_ptr = &lockword_;
73 __asm__ __volatile__
74 ("1: lwarx %0, 0, %1\n\t"
75 "stwcx. %2, 0, %1\n\t"
76 "bne- 1b\n\t"
77 "isync"
78 : "=&r" (r), "=r" (lockword_ptr)
79 : "r" (1), "1" (lockword_ptr)
80 : "memory");
81 #endif
82 #elif COMPILER(MSVC)
83 __asm {
84 mov eax, this ; store &lockword_ (which is this+0) in eax
85 mov ebx, 1 ; store 1 in ebx
86 xchg [eax], ebx ; exchange lockword_ and 1
87 mov r, ebx ; store old value of lockword_ in r
88 }
89 #endif
90 if (r) TCMalloc_SlowLock(&lockword_);
91 }
92
UnlockTCMalloc_SpinLock93 inline void Unlock() {
94 #if COMPILER(GCC)
95 #if CPU(X86) || CPU(X86_64)
96 __asm__ __volatile__
97 ("movl $0, %0"
98 : "=m"(lockword_)
99 : "m" (lockword_)
100 : "memory");
101 #else
102 __asm__ __volatile__
103 ("isync\n\t"
104 "eieio\n\t"
105 "stw %1, %0"
106 #if OS(DARWIN) || CPU(PPC)
107 : "=o" (lockword_)
108 #else
109 : "=m" (lockword_)
110 #endif
111 : "r" (0)
112 : "memory");
113 #endif
114 #elif COMPILER(MSVC)
115 __asm {
116 mov eax, this ; store &lockword_ (which is this+0) in eax
117 mov [eax], 0 ; set lockword_ to 0
118 }
119 #endif
120 }
121 // Report if we think the lock can be held by this thread.
122 // When the lock is truly held by the invoking thread
123 // we will always return true.
124 // Indended to be used as CHECK(lock.IsHeld());
IsHeldTCMalloc_SpinLock125 inline bool IsHeld() const {
126 return lockword_ != 0;
127 }
128
InitTCMalloc_SpinLock129 inline void Init() { lockword_ = 0; }
130
131 volatile unsigned int lockword_;
132 };
133
134 #define SPINLOCK_INITIALIZER { 0 }
135
TCMalloc_SlowLock(volatile unsigned int * lockword)136 static void TCMalloc_SlowLock(volatile unsigned int* lockword) {
137 sched_yield(); // Yield immediately since fast path failed
138 while (true) {
139 int r;
140 #if COMPILER(GCC)
141 #if CPU(X86) || CPU(X86_64)
142 __asm__ __volatile__
143 ("xchgl %0, %1"
144 : "=r"(r), "=m"(*lockword)
145 : "0"(1), "m"(*lockword)
146 : "memory");
147
148 #else
149 int tmp = 1;
150 __asm__ __volatile__
151 ("1: lwarx %0, 0, %1\n\t"
152 "stwcx. %2, 0, %1\n\t"
153 "bne- 1b\n\t"
154 "isync"
155 : "=&r" (r), "=r" (lockword)
156 : "r" (tmp), "1" (lockword)
157 : "memory");
158 #endif
159 #elif COMPILER(MSVC)
160 __asm {
161 mov eax, lockword ; assign lockword into eax
162 mov ebx, 1 ; assign 1 into ebx
163 xchg [eax], ebx ; exchange *lockword and 1
164 mov r, ebx ; store old value of *lockword in r
165 }
166 #endif
167 if (!r) {
168 return;
169 }
170
171 // This code was adapted from the ptmalloc2 implementation of
172 // spinlocks which would sched_yield() upto 50 times before
173 // sleeping once for a few milliseconds. Mike Burrows suggested
174 // just doing one sched_yield() outside the loop and always
175 // sleeping after that. This change helped a great deal on the
176 // performance of spinlocks under high contention. A test program
177 // with 10 threads on a dual Xeon (four virtual processors) went
178 // from taking 30 seconds to 16 seconds.
179
180 // Sleep for a few milliseconds
181 #if OS(WINDOWS)
182 Sleep(2);
183 #else
184 struct timespec tm;
185 tm.tv_sec = 0;
186 tm.tv_nsec = 2000001;
187 nanosleep(&tm, NULL);
188 #endif
189 }
190 }
191
192 #else
193
194 #include <pthread.h>
195
196 // Portable version
197 struct TCMalloc_SpinLock {
198 pthread_mutex_t private_lock_;
199
InitTCMalloc_SpinLock200 inline void Init() {
201 if (pthread_mutex_init(&private_lock_, NULL) != 0) CRASH();
202 }
FinalizeTCMalloc_SpinLock203 inline void Finalize() {
204 if (pthread_mutex_destroy(&private_lock_) != 0) CRASH();
205 }
LockTCMalloc_SpinLock206 inline void Lock() {
207 if (pthread_mutex_lock(&private_lock_) != 0) CRASH();
208 }
UnlockTCMalloc_SpinLock209 inline void Unlock() {
210 if (pthread_mutex_unlock(&private_lock_) != 0) CRASH();
211 }
IsHeldTCMalloc_SpinLock212 bool IsHeld() {
213 if (pthread_mutex_trylock(&private_lock_))
214 return true;
215
216 Unlock();
217 return false;
218 }
219 };
220
221 #define SPINLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
222
223 #endif
224
225 // Corresponding locker object that arranges to acquire a spinlock for
226 // the duration of a C++ scope.
227 class TCMalloc_SpinLockHolder {
228 private:
229 TCMalloc_SpinLock* lock_;
230 public:
TCMalloc_SpinLockHolder(TCMalloc_SpinLock * l)231 inline explicit TCMalloc_SpinLockHolder(TCMalloc_SpinLock* l)
232 : lock_(l) { l->Lock(); }
~TCMalloc_SpinLockHolder()233 inline ~TCMalloc_SpinLockHolder() { lock_->Unlock(); }
234 };
235
236 // Short-hands for convenient use by tcmalloc.cc
237 typedef TCMalloc_SpinLock SpinLock;
238 typedef TCMalloc_SpinLockHolder SpinLockHolder;
239
240 #endif // TCMALLOC_INTERNAL_SPINLOCK_H__
241