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From "Brad Nicholes" <BNICHO...@novell.com>
Subject RE: cvs commit: apr/atomic/netware apr_atomic.c
Date Thu, 28 Mar 2002 15:26:38 GMT
Thanks for the catch on the _inc instead of _dec.  I copied and pasted
the wrong function.  Actually the only reason why I had to implement
apr_atomic_dec was because of the return value.  The NetWare
implementation returns a void where apr_atomic_dec returns an int. 
Since atomic_dec() is a NetWare native function there should be no
problem with a race condition.  The locking is all handled by the OS. 
As far as the _cas goes, this was taken straight from the Unix
implementation.  If it is wrong for NetWare then it is probably wrong
for Unix also.

Brad

Brad Nicholes
Senior Software Engineer
Novell, Inc., a leading provider of Net business solutions
http://www.novell.com 

>>> Ian.Holsman@cnet.com Wednesday, March 27, 2002 5:46:37 PM >>>
 
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hi.

this wont work as you still have race conditions
in the 2 functions you implented (the _dec and _cas)
oh.. and the _dec looks like it is adding instead of subtracting

is novell x86 only ?
I'm thinking of just grabbing freeBSD's atomic implementation
and using that as the default x86 implementation.

> -----Original Message-----
> From: bnicholes@apache.org [mailto:bnicholes@apache.org] 
> Sent: Wednesday, March 27, 2002 3:52 PM
> To: apr-cvs@apache.org 
> Subject: cvs commit: apr/atomic/netware apr_atomic.c
> 
> 
> bnicholes    02/03/27 15:51:51
> 
>   Modified:    .        NWGNUmakefile
>                build    nw_export.inc
>                include  apr_atomic.h
>   Added:       atomic/netware apr_atomic.c
>   Log:
>   Added the NetWare version of atomic.c to the build
>   
>   Revision  Changes    Path
>   1.2       +5 -0      apr/NWGNUmakefile
>   
>   Index: NWGNUmakefile
>  
> ===================================================================
>   RCS file: /home/cvs/apr/NWGNUmakefile,v
>   retrieving revision 1.1
>   retrieving revision 1.2
>   diff -u -r1.1 -r1.2
>   --- NWGNUmakefile	1 Mar 2002 22:25:26 -0000	1.1
>   +++ NWGNUmakefile	27 Mar 2002 23:51:50 -0000	1.2
>   @@ -238,6 +238,7 @@
>    # Paths must all use the '/' character
>    #
>    FILES_lib_objs = \
>   +	$(OBJDIR)/apr_atomic.o \
>    	$(OBJDIR)/apr_cpystrn.o \
>    	$(OBJDIR)/apr_fnmatch.o \
>    	$(OBJDIR)/apr_getpass.o \
>   @@ -317,6 +318,10 @@
>    #
>    # Any specialized rules here
>    #
>   +
>   +$(OBJDIR)/%.o: atomic/netware/%.c $(OBJDIR)\cc.opt
>   +	@echo Compiling $<
>   +	$(CC) atomic\netware\$(<F) -o=$(OBJDIR)\$(@F) @$(OBJDIR)\cc.opt
>    
>    $(OBJDIR)/%.o: strings/%.c $(OBJDIR)\cc.opt
>    	@echo Compiling $<
>   
>   
>   
>   1.4       +1 -0      apr/build/nw_export.inc
>   
>   Index: nw_export.inc
>  
> ===================================================================
>   RCS file: /home/cvs/apr/build/nw_export.inc,v
>   retrieving revision 1.3
>   retrieving revision 1.4
>   diff -u -r1.3 -r1.4
>   --- nw_export.inc	20 Feb 2002 19:58:57 -0000	1.3
>   +++ nw_export.inc	27 Mar 2002 23:51:50 -0000	1.4
>   @@ -10,6 +10,7 @@
>    #undef APR_DECLARE_DATA
>    
>    /* Preprocess all of the standard APR headers. */
>   +#include "apr_atomic.h"
>    #include "apr_compat.h"
>    #include "apr_dso.h"
>    #include "apr_errno.h"
>   
>   
>   
>   1.21      +1 -1      apr/include/apr_atomic.h
>   
>   Index: apr_atomic.h
>  
> ===================================================================
>   RCS file: /home/cvs/apr/include/apr_atomic.h,v
>   retrieving revision 1.20
>   retrieving revision 1.21
>   diff -u -r1.20 -r1.21
>   --- apr_atomic.h	22 Mar 2002 18:51:07 -0000	1.20
>   +++ apr_atomic.h	27 Mar 2002 23:51:51 -0000	1.21
>   @@ -176,7 +176,7 @@
>    #define apr_atomic_t unsigned long
>    
>    #define apr_atomic_add(mem, val)     atomic_add(mem,val)
>   -#define apr_atomic_dec(mem)          atomic_dec(mem)
>   +APR_DECLARE(int) apr_atomic_dec(apr_atomic_t *mem);
>    #define apr_atomic_inc(mem)          atomic_inc(mem)
>    #define apr_atomic_set(mem, val)     (*mem = val)
>    #define apr_atomic_read(mem)         (*mem)
>   
>   
>   
>   1.1                  apr/atomic/netware/apr_atomic.c
>   
>   Index: apr_atomic.c
>  
> ===================================================================
>   /* 
> ====================================================================
>    * The Apache Software License, Version 1.1
>    *
>    * Copyright (c) 2000-2002 The Apache Software Foundation.  
> All rights
>    * reserved.
>    *
>    * Redistribution and use in source and binary forms, with 
> or without
>    * modification, are permitted provided that the following 
> conditions
>    * are met:
>    *
>    * 1. Redistributions of source code must retain the above
> copyright 
>    *    notice, this list of conditions and the following
> disclaimer. 
>    *
>    * 2. Redistributions in binary form must reproduce the 
> above copyright
>    *    notice, this list of conditions and the following 
> disclaimer in
>    *    the documentation and/or other materials provided with the
>    *    distribution.
>    *
>    * 3. The end-user documentation included with the
> redistribution, 
>    *    if any, must include the following acknowledgment:
>    *       "This product includes software developed by the
>    *        Apache Software Foundation (http://www.apache.org/)."
>    *    Alternately, this acknowledgment may appear in the 
> software itself,
>    *    if and wherever such third-party acknowledgments 
> normally appear.
>    *
>    * 4. The names "Apache" and "Apache Software Foundation" must
>    *    not be used to endorse or promote products derived from
> this 
>    *    software without prior written permission. For written
>    *    permission, please contact apache@apache.org.
>    *
>    * 5. Products derived from this software may not be called 
> "Apache",
>    *    nor may "Apache" appear in their name, without prior
> written 
>    *    permission of the Apache Software Foundation.
>    *
>    * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR
> IMPLIED 
>    * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
> WARRANTIES 
>    * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
>    * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION
> OR 
>    * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
> INCIDENTAL, 
>    * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
> NOT 
>    * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
> OF 
>    * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
> CAUSED AND
>    * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
> LIABILITY,
>    * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
> ANY WAY OUT
>    * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
> POSSIBILITY OF
>    * SUCH DAMAGE.
>    * 
> ====================================================================
>    *
>    * This software consists of voluntary contributions made by many
>    * individuals on behalf of the Apache Software Foundation. 
>  For more
>    * information on the Apache Software Foundation, please see
>    * <http://www.apache.org/>.
>    */
>   
>   
>   #include "apr.h"
>   #include "apr_lock.h"
>   #include "apr_thread_mutex.h"
>   #include "apr_atomic.h"
>   
>   #if APR_HAS_THREADS
>   
>   #if defined(APR_ATOMIC_NEED_DEFAULT)  || 
> defined(APR_ATOMIC_NEED_CAS_DEFAULT)
>   
>   #define NUM_ATOMIC_HASH 7
>   /* shift by 2 to get rid of alignment issues */
>   #define ATOMIC_HASH(x) (int)(((long)x>>2)%NUM_ATOMIC_HASH)
>   static apr_thread_mutex_t **hash_mutex;
>   
>   apr_status_t apr_atomic_init(apr_pool_t *p )
>   {
>       int i;
>       apr_status_t rv;
>       hash_mutex =apr_palloc(p,sizeof(apr_thread_mutex_t*) * 
> NUM_ATOMIC_HASH);
>       for (i=0;i<NUM_ATOMIC_HASH;i++) {
>           rv = apr_thread_mutex_create(&(hash_mutex[i]), 
> APR_THREAD_MUTEX_DEFAULT, p);
>           if (rv != APR_SUCCESS)
>              return rv;
>       }
>       return APR_SUCCESS;
>   }
>   #endif /* APR_ATOMIC_NEED_DEFAULT || APR_ATOMIC_NEED_CAS_DEFAULT
> */ 
>   
>   int apr_atomic_dec(apr_atomic_t *mem) 
>   {
>       atomic_inc(mem);
>       return *mem; 
>   }
>   
>   #if defined(APR_ATOMIC_NEED_CAS_DEFAULT)
>   
>   apr_uint32_t apr_atomic_cas(volatile apr_uint32_t *mem,long 
> with, long cmp)
>   {
>       apr_thread_mutex_t *lock = hash_mutex[ATOMIC_HASH(mem)];
>       long prev;
>   
>       if (apr_thread_mutex_lock(lock) == APR_SUCCESS) {
>           prev = *(long*)mem;
>           if ( prev == cmp) {
>               *(long*)mem = with;
>           }
>           apr_thread_mutex_unlock(lock);
>           return prev;
>       }
>       return *(long*)mem;
>   }
>   #endif /* APR_ATOMIC_NEED_CAS_DEFAULT */
>   
>   
>   #endif /* APR_HAS_THREADS */
>   
>   
>   
> 

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