The Tor Browser: nsprpub/pr/src/threads/combined/prustack.c@6474c204b198

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

     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/. */

     6 #include "primpl.h"

     8 /* List of free stack virtual memory chunks */

     9 PRLock *_pr_stackLock;

    10 PRCList _pr_freeStacks = PR_INIT_STATIC_CLIST(&_pr_freeStacks);

    11 PRIntn _pr_numFreeStacks;

    12 PRIntn _pr_maxFreeStacks = 4;

    14 #ifdef DEBUG

    15 /*

    16 ** A variable that can be set via the debugger...

    17 */

    18 PRBool _pr_debugStacks = PR_FALSE;

    19 #endif

    21 /* How much space to leave between the stacks, at each end */

    22 #define REDZONE		(2 << _pr_pageShift)

    24 #define _PR_THREAD_STACK_PTR(_qp) \

    25     ((PRThreadStack*) ((char*) (_qp) - offsetof(PRThreadStack,links)))

    27 void _PR_InitStacks(void)

    28 {

    29     _pr_stackLock = PR_NewLock();

    30 }

    32 void _PR_CleanupStacks(void)

    33 {

    34     if (_pr_stackLock) {

    35         PR_DestroyLock(_pr_stackLock);

    36         _pr_stackLock = NULL;

    37     }

    38 }

    40 /*

    41 ** Allocate a stack for a thread.

    42 */

    43 PRThreadStack *_PR_NewStack(PRUint32 stackSize)

    44 {

    45     PRCList *qp;

    46     PRThreadStack *ts;

    47     PRThread *thr;

    49     /*

    50     ** Trim the list of free stacks. Trim it backwards, tossing out the

    51     ** oldest stack found first (this way more recent stacks have a

    52     ** chance of being present in the data cache).

    53     */

    54     PR_Lock(_pr_stackLock);

    55     qp = _pr_freeStacks.prev;

    56     while ((_pr_numFreeStacks > _pr_maxFreeStacks) && (qp != &_pr_freeStacks)) {

    57 	ts = _PR_THREAD_STACK_PTR(qp);

    58 	thr = _PR_THREAD_STACK_TO_PTR(ts);

    59 	qp = qp->prev;

    60 	/*

    61 	 * skip stacks which are still being used

    62 	 */

    63 	if (thr->no_sched)

    64 		continue;

    65 	PR_REMOVE_LINK(&ts->links);

    67 	/* Give platform OS to clear out the stack for debugging */

    68 	_PR_MD_CLEAR_STACK(ts);

    70 	_pr_numFreeStacks--;

    71 	_PR_DestroySegment(ts->seg);

    72 	PR_DELETE(ts);

    73     }

    75     /*

    76     ** Find a free thread stack. This searches the list of free'd up

    77     ** virtually mapped thread stacks.

    78     */

    79     qp = _pr_freeStacks.next;

    80     ts = 0;

    81     while (qp != &_pr_freeStacks) {

    82 	ts = _PR_THREAD_STACK_PTR(qp);

    83 	thr = _PR_THREAD_STACK_TO_PTR(ts);

    84 	qp = qp->next;

    85 	/*

    86 	 * skip stacks which are still being used

    87 	 */

    88 	if ((!(thr->no_sched)) && ((ts->allocSize - 2*REDZONE) >= stackSize)) {

    89 	    /*

    90 	    ** Found a stack that is not in use and is big enough. Change

    91 	    ** stackSize to fit it.

    92 	    */

    93 	    stackSize = ts->allocSize - 2*REDZONE;

    94 	    PR_REMOVE_LINK(&ts->links);

    95 	    _pr_numFreeStacks--;

    96 	    ts->links.next = 0;

    97 	    ts->links.prev = 0;

    98 	    PR_Unlock(_pr_stackLock);

    99 	    goto done;

   100 	}

   101 	ts = 0;

   102     }

   103     PR_Unlock(_pr_stackLock);

   105     if (!ts) {

   106 	/* Make a new thread stack object. */

   107 	ts = PR_NEWZAP(PRThreadStack);

   108 	if (!ts) {

   109 	    return NULL;

   110 	}

   112 	/*

   113 	** Assign some of the virtual space to the new stack object. We

   114 	** may not get that piece of VM, but if nothing else we will

   115 	** advance the pointer so we don't collide (unless the OS screws

   116 	** up).

   117 	*/

   118 	ts->allocSize = stackSize + 2*REDZONE;

   119 	ts->seg = _PR_NewSegment(ts->allocSize, 0);

   120 	if (!ts->seg) {

   121 	    PR_DELETE(ts);

   122 	    return NULL;

   123 	}

   124 	}

   126   done:

   127     ts->allocBase = (char*)ts->seg->vaddr;

   128     ts->flags = _PR_STACK_MAPPED;

   129     ts->stackSize = stackSize;

   131 #ifdef HAVE_STACK_GROWING_UP

   132     ts->stackTop = ts->allocBase + REDZONE;

   133     ts->stackBottom = ts->stackTop + stackSize;

   134 #else

   135     ts->stackBottom = ts->allocBase + REDZONE;

   136     ts->stackTop = ts->stackBottom + stackSize;

   137 #endif

   139     PR_LOG(_pr_thread_lm, PR_LOG_NOTICE,

   140 	   ("thread stack: base=0x%x limit=0x%x bottom=0x%x top=0x%x\n",

   141 	    ts->allocBase, ts->allocBase + ts->allocSize - 1,

   142 	    ts->allocBase + REDZONE,

   143 	    ts->allocBase + REDZONE + stackSize - 1));

   145     _PR_MD_INIT_STACK(ts,REDZONE);

   147     return ts;

   148 }

   150 /*

   151 ** Free the stack for the current thread

   152 */

   153 void _PR_FreeStack(PRThreadStack *ts)

   154 {

   155     if (!ts) {

   156 	return;

   157     }

   158     if (ts->flags & _PR_STACK_PRIMORDIAL) {

   159 	PR_DELETE(ts);

   160 	return;

   161     }

   163     /*

   164     ** Put the stack on the free list. This is done because we are still

   165     ** using the stack. Next time a thread is created we will trim the

   166     ** list down; it's safe to do it then because we will have had to

   167     ** context switch to a live stack before another thread can be

   168     ** created.

   169     */

   170     PR_Lock(_pr_stackLock);

   171     PR_APPEND_LINK(&ts->links, _pr_freeStacks.prev);

   172     _pr_numFreeStacks++;

   173     PR_Unlock(_pr_stackLock);

   174 }

The Tor Browser / file revision