[patch mingw]: Correct page-size granularity and retry for address-mapping on mingw-hosts.

[Kai Tietz]

Hi,

this patch fixes a latent issue about page-size granularity for
Windows OSes - like Vista, Win7, etc. -
and avoid a race happening for mapping of memory for multiple
instances of compiler.

ChangeLog

2012-11-29  Kai Tietz

	* host-mingw32.c (va_granularity): Make none-const.
	(mingw32_gt_pch_alloc_granularity): Return OS' allocation
	granularity.
	(mingw32_gt_pch_use_address): Retry mapping of used address
	as multiple instances might interfer.

Tested for i686-w64-mingw32, and x86_64-w64-mingw32.  Will apply
tomorrow if there aren't any objections.

Regards,
Kai

Index: host-mingw32.c
===================================================================
--- host-mingw32.c	(Revision 193925)
+++ host-mingw32.c	(Arbeitskopie)
@@ -27,6 +27,7 @@

 #define WIN32_LEAN_AND_MEAN  /* Not so important if we have windows.h.gch.  */
 #include <windows.h>
+#include <stdlib.h>

 static void * mingw32_gt_pch_get_address (size_t, int);
 static int mingw32_gt_pch_use_address (void *, size_t, int, size_t);
@@ -45,7 +46,7 @@
 static const size_t pch_VA_max_size  = 128 * 1024 * 1024;

 /* Granularity for reserving address space.  */
-static const size_t va_granularity = 0x10000;
+static size_t va_granularity = 0x10000;

 /* Print out the GetLastError() translation.  */
 static inline void
@@ -66,8 +67,14 @@
 }

 /* Granularity for reserving address space.  */
-static size_t mingw32_gt_pch_alloc_granularity (void)
+static size_t
+mingw32_gt_pch_alloc_granularity (void)
 {
+  SYSTEM_INFO si;
+
+  GetSystemInfo (&si);
+  va_granularity = (size_t) si.dwAllocationGranularity;
+
   return va_granularity;
 }

@@ -132,6 +139,8 @@
      and earlier, backslashes are invalid in object name.  So, we need
      to check if we are on Windows2000 or higher.  */
   OSVERSIONINFO version_info;
+  int r;
+
   version_info.dwOSVersionInfoSize = sizeof (version_info);

   if (size == 0)
@@ -154,7 +163,6 @@
 		OBJECT_NAME_FMT "%lx", GetCurrentProcessId());
       object_name = local_object_name;
     }
-
   mmap_handle = CreateFileMappingA ((HANDLE) _get_osfhandle (fd), NULL,
 				    PAGE_WRITECOPY | SEC_COMMIT, 0, 0,
 				    object_name);
@@ -164,8 +172,19 @@
       w32_error (__FUNCTION__,  __FILE__, __LINE__, "CreateFileMapping");
       return -1;
     }
-  mmap_addr = MapViewOfFileEx (mmap_handle, FILE_MAP_COPY, 0, offset,
-			       size, addr);
+
+  /* Retry five times, as here might occure a race with multiple gcc's
+     instances at same time.  */
+  for (r = 0; r < 5; r++)
+   {
+      mmap_addr = MapViewOfFileEx (mmap_handle, FILE_MAP_COPY, 0, offset,
+				   size, addr);
+      if (mmap_addr == addr)
+	break;
+      if (r != 4)
+        Sleep (500);
+   }
+
   if (mmap_addr != addr)
     {
       w32_error (__FUNCTION__, __FILE__, __LINE__, "MapViewOfFileEx");