X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/406f54970c00ca178fa918763d943027bd09e3ba..2d36dff11c16369d120b77eda54c35e77d1b8bbb:/src/xbt/mmalloc/mmorecore.c

diff --git a/src/xbt/mmalloc/mmorecore.c b/src/xbt/mmalloc/mmorecore.c
index e1175a7c3d..b99f32259e 100644
--- a/src/xbt/mmalloc/mmorecore.c
+++ b/src/xbt/mmalloc/mmorecore.c
@@ -1,16 +1,14 @@
-/* Support for an sbrk-like function that uses mmap.
-   Copyright 1992, 2000 Free Software Foundation, Inc.
+/* Support for an sbrk-like function that uses mmap. */
 
-   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com */
-
-/* Copyright (c) 2010-2012. The SimGrid Team. All rights reserved.          */
+/* Copyright (c) 2010-2014. The SimGrid Team.
+ * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
-#ifndef MAP_ANONYMOUS
-#define MAP_ANONYMOUS MAP_ANON
-#endif
+/* Copyright 1992, 2000 Free Software Foundation, Inc.
+
+   Contributed by Fred Fish at Cygnus Support.   fnf@cygnus.com */
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>             /* Prototypes for lseek */
@@ -18,18 +16,17 @@
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/mman.h>
+#include <sys/wait.h>
+#include <errno.h>
 
 #include "mmprivate.h"
 
-/* Cache the pagesize for the current host machine.  Note that if the host
-   does not readily provide a getpagesize() function, we need to emulate it
-   elsewhere, not clutter up this file with lots of kluges to try to figure
-   it out. */
-
-static size_t pagesize;
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
 
-#define PAGE_ALIGN(addr) (void*) (((long)(addr) + pagesize - 1) & \
-                                  ~(pagesize - 1))
+#define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) &   \
+                                  ~((long)xbt_pagesize - 1))
 
 /* Return MAP_PRIVATE if MDP represents /dev/zero.  Otherwise, return
    MAP_SHARED.  */
@@ -47,12 +44,17 @@ static size_t pagesize;
                              ? -1                                 \
                              : (MDP) -> fd)
 
-/*  Get core for the memory region specified by MDP, using SIZE as the
-    amount to either add to or subtract from the existing region.  Works
-    like sbrk(), but using mmap().
-
-    It never returns NULL. Instead, it dies verbosely on errors. */
-
+/** @brief Add memoty to this heap
+ *
+ *  Get core for the memory region specified by MDP, using SIZE as the
+ *  amount to either add to or subtract from the existing region.  Works
+ *  like sbrk(), but using mmap().
+ *
+ *  It never returns NULL. Instead, it dies verbosely on errors.
+ *
+ *  @param mdp  The heap
+ *  @param size Bytes to allocate for this heap (or <0 to free memory from this heap)
+ */
 void *mmorecore(struct mdesc *mdp, ssize_t size)
 {
   ssize_t test = 0;
@@ -63,10 +65,6 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
   void *mapto;                  /* Address we actually mapped to */
   char buf = 0;                 /* Single byte to write to extend mapped file */
 
-//  fprintf(stderr,"increase %p by %u\n",mdp,size);
-  if (pagesize == 0)
-    pagesize = getpagesize();
-
   if (size == 0) {
     /* Just return the current "break" value. */
     result = mdp->breakval;
@@ -114,12 +112,15 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
       }
 
       /* Let's call mmap. Note that it is possible that mdp->top
-         is 0. In this case mmap will choose the address for us */
+         is 0. In this case mmap will choose the address for us.
+         This call might very well overwrite an already existing memory mapping
+         (leading to weird bugs).
+       */
       mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
                    MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
                    MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
 
-      if (mapto == (void *) -1/* That's MAP_FAILED */) {
+      if (mapto == MAP_FAILED) {
         char buff[1024];
         fprintf(stderr,"Internal error: mmap returned MAP_FAILED! error: %s\n",strerror(errno));
         sprintf(buff,"cat /proc/%d/maps",getpid());
@@ -137,6 +138,7 @@ void *mmorecore(struct mdesc *mdp, ssize_t size)
       result = (void *) mdp->breakval;
       mdp->breakval = (char *) mdp->breakval + size;
     } else {
+      /* Memory is already mapped, we only need to increase the breakval: */
       result = (void *) mdp->breakval;
       mdp->breakval = (char *) mdp->breakval + size;
     }