prthread.h (10085B)
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* This Source Code Form is subject to the terms of the Mozilla Public 3 * License, v. 2.0. If a copy of the MPL was not distributed with this 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 5 6 #ifndef prthread_h___ 7 #define prthread_h___ 8 9 /* 10 ** API for NSPR threads. On some architectures (Mac OS Classic 11 ** notably) pre-emptibility is not guaranteed. Hard priority scheduling 12 ** is not guaranteed, so programming using priority based synchronization 13 ** is a no-no. 14 ** 15 ** NSPR threads are scheduled based loosely on their client set priority. 16 ** In general, a thread of a higher priority has a statistically better 17 ** chance of running relative to threads of lower priority. However, 18 ** NSPR uses multiple strategies to provide execution vehicles for thread 19 ** abstraction of various host platforms. As it turns out, there is little 20 ** NSPR can do to affect the scheduling attributes of "GLOBAL" threads. 21 ** However, a semblance of GLOBAL threads is used to implement "LOCAL" 22 ** threads. An arbitrary number of such LOCAL threads can be assigned to 23 ** a single GLOBAL thread. 24 ** 25 ** For scheduling, NSPR will attempt to run the highest priority LOCAL 26 ** thread associated with a given GLOBAL thread. It is further assumed 27 ** that the host OS will apply some form of "fair" scheduling on the 28 ** GLOBAL threads. 29 ** 30 ** Threads have a "system flag" which when set indicates the thread 31 ** doesn't count for determining when the process should exit (the 32 ** process exits when the last user thread exits). 33 ** 34 ** Threads also have a "scope flag" which controls whether the threads 35 ** are scheduled in the local scope or scheduled by the OS globally. This 36 ** indicates whether a thread is permanently bound to a native OS thread. 37 ** An unbound thread competes for scheduling resources in the same process. 38 ** 39 ** Another flag is "state flag" which control whether the thread is joinable. 40 ** It allows other threads to wait for the created thread to reach completion. 41 ** 42 ** Threads can have "per-thread-data" attached to them. Each thread has a 43 ** per-thread error number and error string which are updated when NSPR 44 ** operations fail. 45 */ 46 #include "prtypes.h" 47 #include "prinrval.h" 48 49 PR_BEGIN_EXTERN_C 50 51 typedef struct PRThread PRThread; 52 typedef struct PRThreadStack PRThreadStack; 53 54 typedef enum PRThreadType { 55 PR_USER_THREAD, 56 PR_SYSTEM_THREAD 57 } PRThreadType; 58 59 typedef enum PRThreadScope { 60 PR_LOCAL_THREAD, 61 PR_GLOBAL_THREAD, 62 PR_GLOBAL_BOUND_THREAD 63 } PRThreadScope; 64 65 typedef enum PRThreadState { 66 PR_JOINABLE_THREAD, 67 PR_UNJOINABLE_THREAD 68 } PRThreadState; 69 70 typedef enum PRThreadPriority 71 { 72 PR_PRIORITY_FIRST = 0, /* just a placeholder */ 73 PR_PRIORITY_LOW = 0, /* the lowest possible priority */ 74 PR_PRIORITY_NORMAL = 1, /* most common expected priority */ 75 PR_PRIORITY_HIGH = 2, /* slightly more aggressive scheduling */ 76 PR_PRIORITY_URGENT = 3, /* it does little good to have more than one */ 77 PR_PRIORITY_LAST = 3 /* this is just a placeholder */ 78 } PRThreadPriority; 79 80 /* 81 ** Create a new thread: 82 ** "type" is the type of thread to create 83 ** "start(arg)" will be invoked as the threads "main" 84 ** "priority" will be created thread's priority 85 ** "scope" will specify whether the thread is local or global 86 ** "state" will specify whether the thread is joinable or not 87 ** "stackSize" the size of the stack, in bytes. The value can be zero 88 ** and then a machine specific stack size will be chosen. 89 ** 90 ** This can return NULL if some kind of error occurs, such as if memory is 91 ** tight. 92 ** 93 ** If you want the thread to start up waiting for the creator to do 94 ** something, enter a lock before creating the thread and then have the 95 ** threads start routine enter and exit the same lock. When you are ready 96 ** for the thread to run, exit the lock. 97 ** 98 ** If you want to detect the completion of the created thread, the thread 99 ** should be created joinable. Then, use PR_JoinThread to synchrnoize the 100 ** termination of another thread. 101 ** 102 ** When the start function returns the thread exits. If it is the last 103 ** PR_USER_THREAD to exit then the process exits. 104 */ 105 NSPR_API(PRThread*) PR_CreateThread(PRThreadType type, 106 void (PR_CALLBACK *start)(void *arg), 107 void *arg, 108 PRThreadPriority priority, 109 PRThreadScope scope, 110 PRThreadState state, 111 PRUint32 stackSize); 112 113 /* 114 ** Wait for thread termination: 115 ** "thread" is the target thread 116 ** 117 ** This can return PR_FAILURE if no joinable thread could be found 118 ** corresponding to the specified target thread. 119 ** 120 ** The calling thread is blocked until the target thread completes. 121 ** Several threads cannot wait for the same thread to complete; one thread 122 ** will operate successfully and others will terminate with an error PR_FAILURE. 123 ** The calling thread will not be blocked if the target thread has already 124 ** terminated. 125 */ 126 NSPR_API(PRStatus) PR_JoinThread(PRThread *thread); 127 128 /* 129 ** Return the current thread object for the currently running code. 130 ** Never returns NULL. 131 */ 132 NSPR_API(PRThread*) PR_GetCurrentThread(void); 133 #ifndef NO_NSPR_10_SUPPORT 134 #define PR_CurrentThread() PR_GetCurrentThread() /* for nspr1.0 compat. */ 135 #endif /* NO_NSPR_10_SUPPORT */ 136 137 /* 138 ** Get the priority of "thread". 139 */ 140 NSPR_API(PRThreadPriority) PR_GetThreadPriority(const PRThread *thread); 141 142 /* 143 ** Change the priority of the "thread" to "priority". 144 ** 145 ** PR_SetThreadPriority works in a best-effort manner. On some platforms a 146 ** special privilege, such as root access, is required to change thread 147 ** priorities, especially to raise thread priorities. If the caller doesn't 148 ** have enough privileges to change thread priorites, the function has no 149 ** effect except causing a future PR_GetThreadPriority call to return 150 ** |priority|. 151 */ 152 NSPR_API(void) PR_SetThreadPriority(PRThread *thread, PRThreadPriority priority); 153 154 /* 155 ** Set the name of the current thread, which will be visible in a debugger 156 ** and accessible via a call to PR_GetThreadName(). 157 */ 158 NSPR_API(PRStatus) PR_SetCurrentThreadName(const char *name); 159 160 /* 161 ** Return the name of "thread", if set. Otherwise return NULL. 162 */ 163 NSPR_API(const char *) PR_GetThreadName(const PRThread *thread); 164 165 /* 166 ** This routine returns a new index for per-thread-private data table. 167 ** The index is visible to all threads within a process. This index can 168 ** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines 169 ** to save and retrieve data associated with the index for a thread. 170 ** 171 ** Each index is associationed with a destructor function ('dtor'). The function 172 ** may be specified as NULL when the index is created. If it is not NULL, the 173 ** function will be called when: 174 ** - the thread exits and the private data for the associated index 175 ** is not NULL, 176 ** - new thread private data is set and the current private data is 177 ** not NULL. 178 ** 179 ** The index independently maintains specific values for each binding thread. 180 ** A thread can only get access to its own thread-specific-data. 181 ** 182 ** Upon a new index return the value associated with the index for all threads 183 ** is NULL, and upon thread creation the value associated with all indices for 184 ** that thread is NULL. 185 ** 186 ** Returns PR_FAILURE if the total number of indices will exceed the maximun 187 ** allowed. 188 */ 189 typedef void (PR_CALLBACK *PRThreadPrivateDTOR)(void *priv); 190 191 NSPR_API(PRStatus) PR_NewThreadPrivateIndex( 192 PRUintn *newIndex, PRThreadPrivateDTOR destructor); 193 194 /* 195 ** Define some per-thread-private data. 196 ** "tpdIndex" is an index into the per-thread private data table 197 ** "priv" is the per-thread-private data 198 ** 199 ** If the per-thread private data table has a previously registered 200 ** destructor function and a non-NULL per-thread-private data value, 201 ** the destructor function is invoked. 202 ** 203 ** This can return PR_FAILURE if the index is invalid. 204 */ 205 NSPR_API(PRStatus) PR_SetThreadPrivate(PRUintn tpdIndex, void *priv); 206 207 /* 208 ** Recover the per-thread-private data for the current thread. "tpdIndex" is 209 ** the index into the per-thread private data table. 210 ** 211 ** The returned value may be NULL which is indistinguishable from an error 212 ** condition. 213 ** 214 ** A thread can only get access to its own thread-specific-data. 215 */ 216 NSPR_API(void*) PR_GetThreadPrivate(PRUintn tpdIndex); 217 218 /* 219 ** This routine sets the interrupt request for a target thread. The interrupt 220 ** request remains in the thread's state until it is delivered exactly once 221 ** or explicitly canceled. 222 ** 223 ** A thread that has been interrupted will fail all NSPR blocking operations 224 ** that return a PRStatus (I/O, waiting on a condition, etc). 225 ** 226 ** PR_Interrupt may itself fail if the target thread is invalid. 227 */ 228 NSPR_API(PRStatus) PR_Interrupt(PRThread *thread); 229 230 /* 231 ** Clear the interrupt request for the calling thread. If no such request 232 ** is pending, this operation is a noop. 233 */ 234 NSPR_API(void) PR_ClearInterrupt(void); 235 236 /* 237 ** Block the interrupt for the calling thread. 238 */ 239 NSPR_API(void) PR_BlockInterrupt(void); 240 241 /* 242 ** Unblock the interrupt for the calling thread. 243 */ 244 NSPR_API(void) PR_UnblockInterrupt(void); 245 246 /* 247 ** Make the current thread sleep until "ticks" time amount of time 248 ** has expired. If "ticks" is PR_INTERVAL_NO_WAIT then the call is 249 ** equivalent to calling PR_Yield. Calling PR_Sleep with an argument 250 ** equivalent to PR_INTERVAL_NO_TIMEOUT is an error and will result 251 ** in a PR_FAILURE error return. 252 */ 253 NSPR_API(PRStatus) PR_Sleep(PRIntervalTime ticks); 254 255 /* 256 ** Get the scoping of this thread. 257 */ 258 NSPR_API(PRThreadScope) PR_GetThreadScope(const PRThread *thread); 259 260 /* 261 ** Get the type of this thread. 262 */ 263 NSPR_API(PRThreadType) PR_GetThreadType(const PRThread *thread); 264 265 /* 266 ** Get the join state of this thread. 267 */ 268 NSPR_API(PRThreadState) PR_GetThreadState(const PRThread *thread); 269 270 PR_END_EXTERN_C 271 272 #endif /* prthread_h___ */