andre@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
andre@0: /* This Source Code Form is subject to the terms of the Mozilla Public
andre@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
andre@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
andre@0: 
andre@0: #include "primpl.h"
andre@0: 
andre@0: #include <string.h>
andre@0: 
andre@0: /*****************************************************************************/
andre@0: /*****************************************************************************/
andre@0: /************************** File descriptor caching **************************/
andre@0: /*****************************************************************************/
andre@0: /*****************************************************************************/
andre@0: 
andre@0: /*
andre@0: ** This code is built into debuggable versions of NSPR to assist in
andre@0: ** finding misused file descriptors. Since file descritors (PRFileDesc)
andre@0: ** are identified by a pointer to their structure, they can be the
andre@0: ** target of dangling references. Furthermore, NSPR caches and tries
andre@0: ** to aggressively reuse file descriptors, leading to more ambiguity.
andre@0: ** The following code will allow a debugging client to set environment
andre@0: ** variables and control the number of file descriptors that will be
andre@0: ** preserved before they are recycled. The environment variables are
andre@0: ** NSPR_FD_CACHE_SIZE_LOW and NSPR_FD_CACHE_SIZE_HIGH. The former sets
andre@0: ** the number of descriptors NSPR will allocate before beginning to
andre@0: ** recycle. The latter is the maximum number permitted in the cache
andre@0: ** (exclusive of those in use) at a time.
andre@0: */
andre@0: typedef struct _PR_Fd_Cache
andre@0: {
andre@0:     PRLock *ml;
andre@0:     PRIntn count;
andre@0:     PRStack *stack;
andre@0:     PRFileDesc *head, *tail;
andre@0:     PRIntn limit_low, limit_high;
andre@0: } _PR_Fd_Cache;
andre@0: 
andre@0: static _PR_Fd_Cache _pr_fd_cache;
andre@0: static PRFileDesc **stack2fd = &(((PRFileDesc*)NULL)->higher);
andre@0: 
andre@0: 
andre@0: /*
andre@0: ** Get a FileDescriptor from the cache if one exists. If not allocate
andre@0: ** a new one from the heap.
andre@0: */
andre@0: PRFileDesc *_PR_Getfd(void)
andre@0: {
andre@0:     PRFileDesc *fd;
andre@0:     /*
andre@0:     ** $$$
andre@0:     ** This may look a little wasteful. We'll see. Right now I want to
andre@0:     ** be able to toggle between caching and not at runtime to measure
andre@0:     ** the differences. If it isn't too annoying, I'll leave it in.
andre@0:     ** $$$$
andre@0:     **
andre@0:     ** The test is against _pr_fd_cache.limit_high. If that's zero,
andre@0:     ** we're not doing the extended cache but going for performance.
andre@0:     */
andre@0:     if (0 == _pr_fd_cache.limit_high)
andre@0:     {
andre@0:         PRStackElem *pop;
andre@0:         PR_ASSERT(NULL != _pr_fd_cache.stack);
andre@0:         pop = PR_StackPop(_pr_fd_cache.stack);
andre@0:         if (NULL == pop) goto allocate;
andre@0:         fd = (PRFileDesc*)((PRPtrdiff)pop - (PRPtrdiff)stack2fd);
andre@0:     }
andre@0:     else
andre@0:     {
andre@0:         do
andre@0:         {
andre@0:             if (NULL == _pr_fd_cache.head) goto allocate;  /* nothing there */
andre@0:             if (_pr_fd_cache.count < _pr_fd_cache.limit_low) goto allocate;
andre@0: 
andre@0:             /* we "should" be able to extract an fd from the cache */
andre@0:             PR_Lock(_pr_fd_cache.ml);  /* need the lock to do this safely */
andre@0:             fd = _pr_fd_cache.head;  /* protected extraction */
andre@0:             if (NULL == fd)  /* unexpected, but not fatal */
andre@0:             {
andre@0:                 PR_ASSERT(0 == _pr_fd_cache.count);
andre@0:                 PR_ASSERT(NULL == _pr_fd_cache.tail);
andre@0:             }
andre@0:             else
andre@0:             {
andre@0:                 _pr_fd_cache.count -= 1;
andre@0:                 _pr_fd_cache.head = fd->higher;
andre@0:                 if (NULL == _pr_fd_cache.head)
andre@0:                 {
andre@0:                     PR_ASSERT(0 == _pr_fd_cache.count);
andre@0:                     _pr_fd_cache.tail = NULL;
andre@0:                 }
andre@0:                 PR_ASSERT(&_pr_faulty_methods == fd->methods);
andre@0:                 PR_ASSERT(PR_INVALID_IO_LAYER == fd->identity);
andre@0:                 PR_ASSERT(_PR_FILEDESC_FREED == fd->secret->state);
andre@0:             }
andre@0:             PR_Unlock(_pr_fd_cache.ml);
andre@0: 
andre@0:         } while (NULL == fd);  /* then go around and allocate a new one */
andre@0:     }
andre@0: 
andre@0: finished:
andre@0:     fd->dtor = NULL;
andre@0:     fd->lower = fd->higher = NULL;
andre@0:     fd->identity = PR_NSPR_IO_LAYER;
andre@0:     memset(fd->secret, 0, sizeof(PRFilePrivate));
andre@0:     return fd;
andre@0: 
andre@0: allocate:
andre@0:     fd = PR_NEW(PRFileDesc);
andre@0:     if (NULL != fd)
andre@0:     {
andre@0:         fd->secret = PR_NEW(PRFilePrivate);
andre@0:         if (NULL == fd->secret) PR_DELETE(fd);
andre@0:     }
andre@0:     if (NULL != fd) goto finished;
andre@0:     else return NULL;
andre@0: 
andre@0: }  /* _PR_Getfd */
andre@0: 
andre@0: /*
andre@0: ** Return a file descriptor to the cache unless there are too many in
andre@0: ** there already. If put in cache, clear the fields first.
andre@0: */
andre@0: void _PR_Putfd(PRFileDesc *fd)
andre@0: {
andre@0:     PR_ASSERT(PR_NSPR_IO_LAYER == fd->identity);
andre@0:     fd->methods = &_pr_faulty_methods;
andre@0:     fd->identity = PR_INVALID_IO_LAYER;
andre@0:     fd->secret->state = _PR_FILEDESC_FREED;
andre@0: 
andre@0:     if (0 == _pr_fd_cache.limit_high)
andre@0:     {
andre@0:         PR_StackPush(_pr_fd_cache.stack, (PRStackElem*)(&fd->higher));
andre@0:     }
andre@0:     else
andre@0:     {
andre@0:         if (_pr_fd_cache.count > _pr_fd_cache.limit_high)
andre@0:         {
andre@0:             PR_Free(fd->secret);
andre@0:             PR_Free(fd);
andre@0:         }
andre@0:         else
andre@0:         {
andre@0:             PR_Lock(_pr_fd_cache.ml);
andre@0:             if (NULL == _pr_fd_cache.tail)
andre@0:             {
andre@0:                 PR_ASSERT(0 == _pr_fd_cache.count);
andre@0:                 PR_ASSERT(NULL == _pr_fd_cache.head);
andre@0:                 _pr_fd_cache.head = _pr_fd_cache.tail = fd;
andre@0:             }
andre@0:             else
andre@0:             {
andre@0:                 PR_ASSERT(NULL == _pr_fd_cache.tail->higher);
andre@0:                 _pr_fd_cache.tail->higher = fd;
andre@0:                 _pr_fd_cache.tail = fd;  /* new value */
andre@0:             }
andre@0:             fd->higher = NULL;  /* always so */
andre@0:             _pr_fd_cache.count += 1;  /* count the new entry */
andre@0:             PR_Unlock(_pr_fd_cache.ml);
andre@0:         }
andre@0:     }
andre@0: }  /* _PR_Putfd */
andre@0: 
andre@0: PR_IMPLEMENT(PRStatus) PR_SetFDCacheSize(PRIntn low, PRIntn high)
andre@0: {
andre@0:     /*
andre@0:     ** This can be called at any time, may adjust the cache sizes,
andre@0:     ** turn the caches off, or turn them on. It is not dependent
andre@0:     ** on the compilation setting of DEBUG.
andre@0:     */
andre@0:     if (!_pr_initialized) _PR_ImplicitInitialization();
andre@0: 
andre@0:     if (low > high) low = high;  /* sanity check the params */
andre@0:     
andre@0:     PR_Lock(_pr_fd_cache.ml);
andre@0:     if (0 == high)  /* shutting down or staying down */
andre@0:     {
andre@0:         if (0 != _pr_fd_cache.limit_high)  /* shutting down */
andre@0:         {
andre@0:             _pr_fd_cache.limit_high = 0;  /* stop use */
andre@0:             /*
andre@0:             ** Hold the lock throughout - nobody's going to want it
andre@0:             ** other than another caller to this routine. Just don't
andre@0:             ** let that happen.
andre@0:             **
andre@0:             ** Put all the cached fds onto the new cache.
andre@0:             */
andre@0:             while (NULL != _pr_fd_cache.head)
andre@0:             {
andre@0:                 PRFileDesc *fd = _pr_fd_cache.head;
andre@0:                 _pr_fd_cache.head = fd->higher;
andre@0:                 PR_StackPush(_pr_fd_cache.stack, (PRStackElem*)(&fd->higher));
andre@0:             }
andre@0:             _pr_fd_cache.limit_low = 0;
andre@0:             _pr_fd_cache.tail = NULL;
andre@0:             _pr_fd_cache.count = 0;
andre@0:         }
andre@0:     }
andre@0:     else  /* starting up or just adjusting parameters */
andre@0:     {
andre@0:         PRBool was_using_stack = (0 == _pr_fd_cache.limit_high);
andre@0:         _pr_fd_cache.limit_low = low;
andre@0:         _pr_fd_cache.limit_high = high;
andre@0:         if (was_using_stack)  /* was using stack - feed into cache */
andre@0:         {
andre@0:             PRStackElem *pop;
andre@0:             while (NULL != (pop = PR_StackPop(_pr_fd_cache.stack)))
andre@0:             {
andre@0:                 PRFileDesc *fd = (PRFileDesc*)
andre@0:                     ((PRPtrdiff)pop - (PRPtrdiff)stack2fd);
andre@0:                 if (NULL == _pr_fd_cache.tail) _pr_fd_cache.tail = fd;
andre@0:                 fd->higher = _pr_fd_cache.head;
andre@0:                 _pr_fd_cache.head = fd;
andre@0:                 _pr_fd_cache.count += 1;
andre@0:             }
andre@0:         }
andre@0:     }
andre@0:     PR_Unlock(_pr_fd_cache.ml);
andre@0:     return PR_SUCCESS;
andre@0: }  /* PR_SetFDCacheSize */
andre@0: 
andre@0: void _PR_InitFdCache(void)
andre@0: {
andre@0:     /*
andre@0:     ** The fd caching is enabled by default for DEBUG builds,
andre@0:     ** disabled by default for OPT builds. That default can
andre@0:     ** be overridden at runtime using environment variables
andre@0:     ** or a super-wiz-bang API.
andre@0:     */
andre@0:     const char *low = PR_GetEnv("NSPR_FD_CACHE_SIZE_LOW");
andre@0:     const char *high = PR_GetEnv("NSPR_FD_CACHE_SIZE_HIGH");
andre@0: 
andre@0:     /* 
andre@0:     ** _low is allowed to be zero, _high is not.
andre@0:     ** If _high is zero, we're not doing the caching.
andre@0:     */
andre@0: 
andre@0:     _pr_fd_cache.limit_low = 0;
andre@0: #if defined(DEBUG)
andre@0:     _pr_fd_cache.limit_high = FD_SETSIZE;
andre@0: #else
andre@0:     _pr_fd_cache.limit_high = 0;
andre@0: #endif  /* defined(DEBUG) */
andre@0: 
andre@0:     if (NULL != low) _pr_fd_cache.limit_low = atoi(low);
andre@0:     if (NULL != high) _pr_fd_cache.limit_high = atoi(high);
andre@0: 
andre@0:     if (_pr_fd_cache.limit_low < 0)
andre@0:         _pr_fd_cache.limit_low = 0;
andre@0:     if (_pr_fd_cache.limit_low > FD_SETSIZE)
andre@0:         _pr_fd_cache.limit_low = FD_SETSIZE;
andre@0: 
andre@0:     if (_pr_fd_cache.limit_high > FD_SETSIZE)
andre@0:         _pr_fd_cache.limit_high = FD_SETSIZE;
andre@0: 
andre@0:     if (_pr_fd_cache.limit_high < _pr_fd_cache.limit_low)
andre@0:         _pr_fd_cache.limit_high = _pr_fd_cache.limit_low;
andre@0: 
andre@0:     _pr_fd_cache.ml = PR_NewLock();
andre@0:     PR_ASSERT(NULL != _pr_fd_cache.ml);
andre@0:     _pr_fd_cache.stack = PR_CreateStack("FD");
andre@0:     PR_ASSERT(NULL != _pr_fd_cache.stack);
andre@0: 
andre@0: }  /* _PR_InitFdCache */
andre@0: 
andre@0: void _PR_CleanupFdCache(void)
andre@0: {
andre@0:     PRFileDesc *fd, *next;
andre@0:     PRStackElem *pop;
andre@0: 
andre@0:     for (fd = _pr_fd_cache.head; fd != NULL; fd = next)
andre@0:     {
andre@0:         next = fd->higher;
andre@0:         PR_DELETE(fd->secret);
andre@0:         PR_DELETE(fd);
andre@0:     }
andre@0:     _pr_fd_cache.head = NULL;
andre@0:     _pr_fd_cache.tail = NULL;
andre@0:     _pr_fd_cache.count = 0;
andre@0:     PR_DestroyLock(_pr_fd_cache.ml);
andre@0:     _pr_fd_cache.ml = NULL;
andre@0:     while ((pop = PR_StackPop(_pr_fd_cache.stack)) != NULL)
andre@0:     {
andre@0:         fd = (PRFileDesc*)((PRPtrdiff)pop - (PRPtrdiff)stack2fd);
andre@0:         PR_DELETE(fd->secret);
andre@0:         PR_DELETE(fd);
andre@0:     }
andre@0:     PR_DestroyStack(_pr_fd_cache.stack);
andre@0:     _pr_fd_cache.stack = NULL;
andre@0: }  /* _PR_CleanupFdCache */
andre@0: 
andre@0: /* prfdcach.c */