The Tor Browser: nsprpub/pr/include/prthread.h@44a2da4a2ab2 (annotated)

nsprpub/pr/include/prthread.h@44a2da4a2ab2 (annotated)

nsprpub/pr/include/prthread.h

Fri, 16 Jan 2015 04:50:19 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 04:50:19 +0100
branch: TOR_BUG_9701
changeset 13: 44a2da4a2ab2
permissions: -rw-r--r--

Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #ifndef prthread_h___
 #define prthread_h___
 /*
 ** API for NSPR threads. On some architectures (Mac OS Classic
 ** notably) pre-emptibility is not guaranteed. Hard priority scheduling
 ** is not guaranteed, so programming using priority based synchronization
 ** is a no-no.
 **
 ** NSPR threads are scheduled based loosely on their client set priority.
 ** In general, a thread of a higher priority has a statistically better
 ** chance of running relative to threads of lower priority. However,
 ** NSPR uses multiple strategies to provide execution vehicles for thread
 ** abstraction of various host platforms. As it turns out, there is little
 ** NSPR can do to affect the scheduling attributes of "GLOBAL" threads.
 ** However, a semblance of GLOBAL threads is used to implement "LOCAL"
 ** threads. An arbitrary number of such LOCAL threads can be assigned to
 ** a single GLOBAL thread.
 **
 ** For scheduling, NSPR will attempt to run the highest priority LOCAL
 ** thread associated with a given GLOBAL thread. It is further assumed
 ** that the host OS will apply some form of "fair" scheduling on the
 ** GLOBAL threads.
 **
 ** Threads have a "system flag" which when set indicates the thread
 ** doesn't count for determining when the process should exit (the
 ** process exits when the last user thread exits).
 **
 ** Threads also have a "scope flag" which controls whether the threads
 ** are scheduled in the local scope or scheduled by the OS globally. This
 ** indicates whether a thread is permanently bound to a native OS thread.
 ** An unbound thread competes for scheduling resources in the same process.
 **
 ** Another flag is "state flag" which control whether the thread is joinable.
 ** It allows other threads to wait for the created thread to reach completion.
 **
 ** Threads can have "per-thread-data" attached to them. Each thread has a
 ** per-thread error number and error string which are updated when NSPR
 ** operations fail.
 */
 #include "prtypes.h"
 #include "prinrval.h"
 PR_BEGIN_EXTERN_C
 typedef struct PRThread PRThread;
 typedef struct PRThreadStack PRThreadStack;
 typedef enum PRThreadType {
     PR_USER_THREAD,
     PR_SYSTEM_THREAD
 } PRThreadType;
 typedef enum PRThreadScope {
     PR_LOCAL_THREAD,
     PR_GLOBAL_THREAD,
     PR_GLOBAL_BOUND_THREAD
 } PRThreadScope;
 typedef enum PRThreadState {
     PR_JOINABLE_THREAD,
     PR_UNJOINABLE_THREAD
 } PRThreadState;
 typedef enum PRThreadPriority
 {
     PR_PRIORITY_FIRST = 0,      /* just a placeholder */
     PR_PRIORITY_LOW = 0,        /* the lowest possible priority */
     PR_PRIORITY_NORMAL = 1,     /* most common expected priority */
     PR_PRIORITY_HIGH = 2,       /* slightly more aggressive scheduling */
     PR_PRIORITY_URGENT = 3,     /* it does little good to have more than one */
     PR_PRIORITY_LAST = 3        /* this is just a placeholder */
 } PRThreadPriority;
 /*
 ** Create a new thread:
 **     "type" is the type of thread to create
 **     "start(arg)" will be invoked as the threads "main"
 **     "priority" will be created thread's priority
 **     "scope" will specify whether the thread is local or global
 **     "state" will specify whether the thread is joinable or not
 **     "stackSize" the size of the stack, in bytes. The value can be zero
 **        and then a machine specific stack size will be chosen.
 **
 ** This can return NULL if some kind of error occurs, such as if memory is
 ** tight.
 **
 ** If you want the thread to start up waiting for the creator to do
 ** something, enter a lock before creating the thread and then have the
 ** threads start routine enter and exit the same lock. When you are ready
 ** for the thread to run, exit the lock.
 **
 ** If you want to detect the completion of the created thread, the thread
 ** should be created joinable.  Then, use PR_JoinThread to synchrnoize the
 ** termination of another thread.
 **
 ** When the start function returns the thread exits. If it is the last
 ** PR_USER_THREAD to exit then the process exits.
 */
 NSPR_API(PRThread*) PR_CreateThread(PRThreadType type,
                      void (PR_CALLBACK *start)(void *arg),
                      void *arg,
                      PRThreadPriority priority,
                      PRThreadScope scope,
                      PRThreadState state,
                      PRUint32 stackSize);
 /*
 ** Wait for thread termination:
 **     "thread" is the target thread
 **
 ** This can return PR_FAILURE if no joinable thread could be found
 ** corresponding to the specified target thread.
 **
 ** The calling thread is blocked until the target thread completes.
 ** Several threads cannot wait for the same thread to complete; one thread
 ** will operate successfully and others will terminate with an error PR_FAILURE.
 ** The calling thread will not be blocked if the target thread has already
 ** terminated.
 */
 NSPR_API(PRStatus) PR_JoinThread(PRThread *thread);
 /*
 ** Return the current thread object for the currently running code.
 ** Never returns NULL.
 */
 NSPR_API(PRThread*) PR_GetCurrentThread(void);
 #ifndef NO_NSPR_10_SUPPORT
 #define PR_CurrentThread() PR_GetCurrentThread() /* for nspr1.0 compat. */
 #endif /* NO_NSPR_10_SUPPORT */
 /*
 ** Get the priority of "thread".
 */
 NSPR_API(PRThreadPriority) PR_GetThreadPriority(const PRThread *thread);
 /*
 ** Change the priority of the "thread" to "priority".
 **
 ** PR_SetThreadPriority works in a best-effort manner. On some platforms a
 ** special privilege, such as root access, is required to change thread
 ** priorities, especially to raise thread priorities. If the caller doesn't
 ** have enough privileges to change thread priorites, the function has no
 ** effect except causing a future PR_GetThreadPriority call to return
 ** |priority|.
 */
 NSPR_API(void) PR_SetThreadPriority(PRThread *thread, PRThreadPriority priority);
 /*
 ** Set the name of the current thread, which will be visible in a debugger
 ** and accessible via a call to PR_GetThreadName().
 */
 NSPR_API(PRStatus) PR_SetCurrentThreadName(const char *name);
 /*
 ** Return the name of "thread", if set.  Otherwise return NULL.
 */
 NSPR_API(const char *) PR_GetThreadName(const PRThread *thread);
 /*
 ** This routine returns a new index for per-thread-private data table.
 ** The index is visible to all threads within a process. This index can
 ** be used with the PR_SetThreadPrivate() and PR_GetThreadPrivate() routines
 ** to save and retrieve data associated with the index for a thread.
 **
 ** Each index is associationed with a destructor function ('dtor'). The function
 ** may be specified as NULL when the index is created. If it is not NULL, the
 ** function will be called when:
 **      - the thread exits and the private data for the associated index
 **        is not NULL,
 **      - new thread private data is set and the current private data is
 **        not NULL.
 **
 ** The index independently maintains specific values for each binding thread.
 ** A thread can only get access to its own thread-specific-data.
 **
 ** Upon a new index return the value associated with the index for all threads
 ** is NULL, and upon thread creation the value associated with all indices for
 ** that thread is NULL.
 **
 ** Returns PR_FAILURE if the total number of indices will exceed the maximun
 ** allowed.
 */
 typedef void (PR_CALLBACK *PRThreadPrivateDTOR)(void *priv);
 NSPR_API(PRStatus) PR_NewThreadPrivateIndex(
     PRUintn *newIndex, PRThreadPrivateDTOR destructor);
 /*
 ** Define some per-thread-private data.
 **     "tpdIndex" is an index into the per-thread private data table
 **     "priv" is the per-thread-private data
 **
 ** If the per-thread private data table has a previously registered
 ** destructor function and a non-NULL per-thread-private data value,
 ** the destructor function is invoked.
 **
 ** This can return PR_FAILURE if the index is invalid.
 */
 NSPR_API(PRStatus) PR_SetThreadPrivate(PRUintn tpdIndex, void *priv);
 /*
 ** Recover the per-thread-private data for the current thread. "tpdIndex" is
 ** the index into the per-thread private data table.
 **
 ** The returned value may be NULL which is indistinguishable from an error
 ** condition.
 **
 ** A thread can only get access to its own thread-specific-data.
 */
 NSPR_API(void*) PR_GetThreadPrivate(PRUintn tpdIndex);
 /*
 ** This routine sets the interrupt request for a target thread. The interrupt
 ** request remains in the thread's state until it is delivered exactly once
 ** or explicitly canceled.
 **
 ** A thread that has been interrupted will fail all NSPR blocking operations
 ** that return a PRStatus (I/O, waiting on a condition, etc).
 **
 ** PR_Interrupt may itself fail if the target thread is invalid.
 */
 NSPR_API(PRStatus) PR_Interrupt(PRThread *thread);
 /*
 ** Clear the interrupt request for the calling thread. If no such request
 ** is pending, this operation is a noop.
 */
 NSPR_API(void) PR_ClearInterrupt(void);
 /*
 ** Block the interrupt for the calling thread.
 */
 NSPR_API(void) PR_BlockInterrupt(void);
 /*
 ** Unblock the interrupt for the calling thread.
 */
 NSPR_API(void) PR_UnblockInterrupt(void);
 /*
 ** Make the current thread sleep until "ticks" time amount of time
 ** has expired. If "ticks" is PR_INTERVAL_NO_WAIT then the call is
 ** equivalent to calling PR_Yield. Calling PR_Sleep with an argument
 ** equivalent to PR_INTERVAL_NO_TIMEOUT is an error and will result
 ** in a PR_FAILURE error return.
 */
 NSPR_API(PRStatus) PR_Sleep(PRIntervalTime ticks);
 /*
 ** Get the scoping of this thread.
 */
 NSPR_API(PRThreadScope) PR_GetThreadScope(const PRThread *thread);
 /*
 ** Get the type of this thread.
 */
 NSPR_API(PRThreadType) PR_GetThreadType(const PRThread *thread);
 /*
 ** Get the join state of this thread.
 */
 NSPR_API(PRThreadState) PR_GetThreadState(const PRThread *thread);
 PR_END_EXTERN_C
 #endif /* prthread_h___ */

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nsprpub/pr/include/prthread.h@44a2da4a2ab2 (annotated)

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