nsprpub/pr/include/prthread.h

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  37
  38 #ifndef prthread_h___
  39 #define prthread_h___
  40
  41 /*
  42 ** API for NSPR threads. On some architectures (MAC and WIN16
  43 ** notably) pre-emptibility is not guaranteed. Hard priority scheduling
  44 ** is not guaranteed, so programming using priority based synchronization
  45 ** is a no-no.
  46 **
  47 ** NSPR threads are scheduled based loosely on their client set priority.
  48 ** In general, a thread of a higher priority has a statistically better
  49 ** chance of running relative to threads of lower priority. However,
  50 ** NSPR uses multiple strategies to provide execution vehicles for thread
  51 ** abstraction of various host platforms. As it turns out, there is little
  52 ** NSPR can do to affect the scheduling attributes of "GLOBAL" threads.
  53 ** However, a semblance of GLOBAL threads is used to implement "LOCAL"
  54 ** threads. An arbitrary number of such LOCAL threads can be assigned to
  55 ** a single GLOBAL thread.
  56 **
  57 ** For scheduling, NSPR will attempt to run the highest priority LOCAL
  58 ** thread associated with a given GLOBAL thread. It is further assumed
  59 ** that the host OS will apply some form of "fair" scheduling on the
  60 ** GLOBAL threads.
  61 **
  62 ** Threads have a "system flag" which when set indicates the thread
  63 ** doesn't count for determining when the process should exit (the
  64 ** process exits when the last user thread exits).
  65 **
  66 ** Threads also have a "scope flag" which controls whether the threads
  67 ** are scheduled in the local scope or scheduled by the OS globally. This
  68 ** indicates whether a thread is permanently bound to a native OS thread.
  69 ** An unbound thread competes for scheduling resources in the same process.
  70 **
  71 ** Another flag is "state flag" which control whether the thread is joinable.
  72 ** It allows other threads to wait for the created thread to reach completion.
  73 **
  74 ** Threads can have "per-thread-data" attached to them. Each thread has a
  75 ** per-thread error number and error string which are updated when NSPR
  76 ** operations fail.
  77 */
  78 #include "prtypes.h"
  79 #include "prinrval.h"
  80
  81 PR_BEGIN_EXTERN_C
  82
  83 typedef struct PRThread PRThread;
  84 typedef struct PRThreadStack PRThreadStack;
  85
  86 typedef enum PRThreadType {
  87     PR_USER_THREAD,
  88     PR_SYSTEM_THREAD
  89 } PRThreadType;
  90
  91 typedef enum PRThreadScope {
  92     PR_LOCAL_THREAD,
  93     PR_GLOBAL_THREAD,
  94     PR_GLOBAL_BOUND_THREAD
  95 } PRThreadScope;
  96
  97 typedef enum PRThreadState {
  98     PR_JOINABLE_THREAD,
  99     PR_UNJOINABLE_THREAD
 100 } PRThreadState;
 101
 102 typedef enum PRThreadPriority
 103 {
 104     PR_PRIORITY_FIRST = 0,      /* just a placeholder */
 105     PR_PRIORITY_LOW = 0,        /* the lowest possible priority */
 106     PR_PRIORITY_NORMAL = 1,     /* most common expected priority */
 107     PR_PRIORITY_HIGH = 2,       /* slightly more aggressive scheduling */
 108     PR_PRIORITY_URGENT = 3,     /* it does little good to have more than one */
 109     PR_PRIORITY_LAST = 3        /* this is just a placeholder */
 110 } PRThreadPriority;
 111
 112 /*
 113 ** Create a new thread:
 114 **     "type" is the type of thread to create
 115 **     "start(arg)" will be invoked as the threads "main"
 116 **     "priority" will be created thread's priority
 117 **     "scope" will specify whether the thread is local or global
 118 **     "state" will specify whether the thread is joinable or not
 119 **     "stackSize" the size of the stack, in bytes. The value can be zero
 120 **        and then a machine specific stack size will be chosen.
 121 **
 122 ** This can return NULL if some kind of error occurs, such as if memory is
 123 ** tight.
 124 **
 125 ** If you want the thread to start up waiting for the creator to do
 126 ** something, enter a lock before creating the thread and then have the
 127 ** threads start routine enter and exit the same lock. When you are ready
 128 ** for the thread to run, exit the lock.
 129 **
 130 ** If you want to detect the completion of the created thread, the thread
 131 ** should be created joinable.  Then, use PR_JoinThread to synchrnoize the
 132 ** termination of another thread.
 133 **
 134 ** When the start function returns the thread exits. If it is the last
 135 ** PR_USER_THREAD to exit then the process exits.
 136 */
 137 NSPR_API(PRThread*) PR_CreateThread(PRThreadType type,
 138                      void (PR_CALLBACK *start)(void *arg),
 139                      void *arg,
 140                      PRThreadPriority priority,
 141                      PRThreadScope scope,
 142                      PRThreadState state,
 143                      PRUint32 stackSize);
 144
 145 /*
 146 ** Wait for thread termination:
 147 **     "thread" is the target thread
 148 **
 149 ** This can return PR_FAILURE if no joinable thread could be found
 150 ** corresponding to the specified target thread.
 151 **
 152 ** The calling thread is blocked until the target thread completes.
 153 ** Several threads cannot wait for the same thread to complete; one thread
 154 ** will operate successfully and others will terminate with an error PR_FAILURE.
 155 ** The calling thread will not be blocked if the target thread has already
 156 ** terminated.
 157 */
 158 NSPR_API(PRStatus) PR_JoinThread(PRThread *thread);
 159
 160 /*
 161 ** Return the current thread object for the currently running code.
 162 ** Never returns NULL.
 163 */
 164 NSPR_API(PRThread*) PR_GetCurrentThread(void);
 165 #ifndef NO_NSPR_10_SUPPORT
 166 #define PR_CurrentThread() PR_GetCurrentThread() /* for nspr1.0 compat. */
 167 #endif /* NO_NSPR_10_SUPPORT */
 168
 169 /*
 170 ** Get the priority of "thread".
 171 */
 172 NSPR_API(PRThreadPriority) PR_GetThreadPriority(const PRThread *thread);
 173
 174 /*
 175 ** Change the priority of the "thread" to "priority".
 176 */
 177 NSPR_API(void) PR_SetThreadPriority(PRThread *thread, PRThreadPriority priority);
 178
 179 /*
 180 ** This routine returns a new index for per-thread-private data table.
 181 ** The index is visible to all threads within a process. This index can
 182 ** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines
 183 ** to save and retrieve data associated with the index for a thread.
 184 **
 185 ** Each index is associationed with a destructor function ('dtor'). The function
 186 ** may be specified as NULL when the index is created. If it is not NULL, the
 187 ** function will be called when:
 188 **      - the thread exits and the private data for the associated index
 189 **        is not NULL,
 190 **      - new thread private data is set and the current private data is
 191 **        not NULL.
 192 **
 193 ** The index independently maintains specific values for each binding thread.
 194 ** A thread can only get access to its own thread-specific-data.
 195 **
 196 ** Upon a new index return the value associated with the index for all threads
 197 ** is NULL, and upon thread creation the value associated with all indices for
 198 ** that thread is NULL.
 199 **
 200 ** Returns PR_FAILURE if the total number of indices will exceed the maximun
 201 ** allowed.
 202 */
 203 typedef void (PR_CALLBACK *PRThreadPrivateDTOR)(void *priv);
 204
 205 NSPR_API(PRStatus) PR_NewThreadPrivateIndex(
 206     PRUintn *newIndex, PRThreadPrivateDTOR destructor);
 207
 208 /*
 209 ** Define some per-thread-private data.
 210 **     "tpdIndex" is an index into the per-thread private data table
 211 **     "priv" is the per-thread-private data
 212 **
 213 ** If the per-thread private data table has a previously registered
 214 ** destructor function and a non-NULL per-thread-private data value,
 215 ** the destructor function is invoked.
 216 **
 217 ** This can return PR_FAILURE if the index is invalid.
 218 */
 219 NSPR_API(PRStatus) PR_SetThreadPrivate(PRUintn tpdIndex, void *priv);
 220
 221 /*
 222 ** Recover the per-thread-private data for the current thread. "tpdIndex" is
 223 ** the index into the per-thread private data table.
 224 **
 225 ** The returned value may be NULL which is indistinguishable from an error
 226 ** condition.
 227 **
 228 ** A thread can only get access to its own thread-specific-data.
 229 */
 230 NSPR_API(void*) PR_GetThreadPrivate(PRUintn tpdIndex);
 231
 232 /*
 233 ** This routine sets the interrupt request for a target thread. The interrupt
 234 ** request remains in the thread's state until it is delivered exactly once
 235 ** or explicitly canceled.
 236 **
 237 ** A thread that has been interrupted will fail all NSPR blocking operations
 238 ** that return a PRStatus (I/O, waiting on a condition, etc).
 239 **
 240 ** PR_Interrupt may itself fail if the target thread is invalid.
 241 */
 242 NSPR_API(PRStatus) PR_Interrupt(PRThread *thread);
 243
 244 /*
 245 ** Clear the interrupt request for the calling thread. If no such request
 246 ** is pending, this operation is a noop.
 247 */
 248 NSPR_API(void) PR_ClearInterrupt(void);
 249
 250 /*
 251 ** Block the interrupt for the calling thread.
 252 */
 253 NSPR_API(void) PR_BlockInterrupt(void);
 254
 255 /*
 256 ** Unblock the interrupt for the calling thread.
 257 */
 258 NSPR_API(void) PR_UnblockInterrupt(void);
 259
 260 /*
 261 ** Make the current thread sleep until "ticks" time amount of time
 262 ** has expired. If "ticks" is PR_INTERVAL_NO_WAIT then the call is
 263 ** equivalent to calling PR_Yield. Calling PR_Sleep with an argument
 264 ** equivalent to PR_INTERVAL_NO_TIMEOUT is an error and will result
 265 ** in a PR_FAILURE error return.
 266 */
 267 NSPR_API(PRStatus) PR_Sleep(PRIntervalTime ticks);
 268
 269 /*
 270 ** Get the scoping of this thread.
 271 */
 272 NSPR_API(PRThreadScope) PR_GetThreadScope(const PRThread *thread);
 273
 274 /*
 275 ** Get the type of this thread.
 276 */
 277 NSPR_API(PRThreadType) PR_GetThreadType(const PRThread *thread);
 278
 279 /*
 280 ** Get the join state of this thread.
 281 */
 282 NSPR_API(PRThreadState) PR_GetThreadState(const PRThread *thread);
 283
 284 PR_END_EXTERN_C
 285
 286 #endif /* prthread_h___ */