On 30/03/2011 22:29, Christopher Faylor wrote:
> On Wed, Mar 30, 2011 at 11:15:56PM +0200, Corinna Vinschen wrote:
>> Chris, are you going to take a look into this patch?
>
> yep.
Attached is an updated version of the patch which fixes the warning identified
by Yaakov.
I've also attached a slightly cleaned up version of the additional fork
debugging output patch I was using.
2011-03-12 Jon TURNEY <jon.tur...@dronecode.org.uk>
* dll_init.cc (reserve_at, release_at): New functions.
(load_after_fork): Make a 3rd pass at trying to load the DLL in
the right place.
Index: cygwin/dll_init.cc
===================================================================
--- cygwin/dll_init.cc.orig 2011-03-27 18:19:06.000000000 +0100
+++ cygwin/dll_init.cc 2011-03-28 23:43:47.125000000 +0100
@@ -254,15 +254,47 @@
}
}
+/* Mark one page at "here" as reserved. This may force
+ Windows NT to load a DLL elsewhere. */
+static DWORD
+reserve_at (const PWCHAR name, DWORD here)
+{
+ DWORD size;
+ MEMORY_BASIC_INFORMATION mb;
+
+ if (!VirtualQuery ((void *) here, &mb, sizeof (mb)))
+ size = 64 * 1024;
+
+ if (mb.State != MEM_FREE)
+ return 0;
+
+ size = mb.RegionSize;
+ if (!VirtualAlloc ((void *) here, size, MEM_RESERVE, PAGE_NOACCESS))
+ api_fatal ("couldn't allocate memory %p(%d) for '%W' alignment, %E\n",
+ here, size, name);
+ return here;
+}
+
+/* Release the memory previously allocated by "reserve_at" above. */
+static void
+release_at (const PWCHAR name, DWORD here)
+{
+ if (!VirtualFree ((void *) here, 0, MEM_RELEASE))
+ api_fatal ("couldn't release memory %p for '%W' alignment, %E\n",
+ here, name);
+}
+
/* Reload DLLs after a fork. Iterates over the list of dynamically loaded
DLLs and attempts to load them in the same place as they were loaded in the
parent. */
void
dll_list::load_after_fork (HANDLE parent)
{
+ DWORD preferred_block = 0;
+
for (dll *d = &dlls.start; (d = d->next) != NULL; )
if (d->type == DLL_LOAD)
- for (int i = 0; i < 2; i++)
+ for (int i = 0; i < 3; i++)
{
/* See if DLL will load in proper place. If so, free it and reload
it the right way.
@@ -281,15 +313,26 @@
if (h == d->handle)
h = LoadLibraryW (d->name);
}
- /* If we reached here on the second iteration of the for loop
+
+ /* If we reached here on subsequent iterations of the for loop
then there is a lot of memory to release. */
if (i > 0)
release_upto (d->name, (DWORD) d->handle);
+
+ /* If we reached here on the last iteration of the for loop
+ then there's a bit of memory to release */
+ if (i > 1)
+ {
+ if (preferred_block)
+ release_at(d->name, preferred_block);
+ preferred_block = 0;
+ }
+
if (h == d->handle)
break; /* Success */
- if (i > 0)
- /* We tried once to relocate the dll and it failed. */
+ if (i > 1)
+ /* We tried to relocate the dll and it failed. */
api_fatal ("unable to remap %W to same address as parent: %p != %p",
d->name, d->handle, h);
@@ -299,6 +342,15 @@
second DLL always loads into a different location. So, block all
of the memory up to the new load address and try again. */
reserve_upto (d->name, (DWORD) d->handle);
+
+ /* Dll *still* loaded in the wrong place. This can happen if it
+ couldn't load at the preferred base in the parent, but can in
+ the child, due to ordering differences. Block memory at it's
+ preferred address and try again. */
+ if (i > 0)
+ {
+ preferred_block = reserve_at(d->name, (DWORD)h);
+ }
}
in_forkee = false;
}
2011-04-04 Jon TURNEY <jon.tur...@dronecode.org.uk>
* dll_init.cc (load_after_fork): Add some debug output...
* environ.cc (parse_thing): ... controlled by 'forkdebug' setting
Index: winsup/cygwin/dll_init.cc
===================================================================
--- winsup.orig/cygwin/dll_init.cc 2011-04-02 21:40:02.000000000 +0100
+++ winsup/cygwin/dll_init.cc 2011-04-03 18:47:09.781250000 +0100
@@ -29,6 +29,7 @@
dll_list dlls;
static bool dll_global_dtors_recorded;
+bool fork_debug = FALSE;
/* Run destructors for all DLLs on exit. */
void
@@ -307,6 +308,8 @@
above, the second LoadLibrary will not execute its startup code
unless it is first unloaded. */
HMODULE h = LoadLibraryExW (d->name, NULL,
DONT_RESOLVE_DLL_REFERENCES);
+ if (fork_debug)
+ system_printf("LoadLibrary %W @ %p (pass %d)", d->name, h, i);
if (!h)
system_printf ("can't reload %W, %E", d->name);
@@ -332,7 +335,11 @@
}
if (h == d->handle)
- break; /* Success */
+ {
+ if (fork_debug)
+ system_printf("successfully mapped %W @ %p", d->name,
d->handle);
+ break; /* Success */
+ }
if (i > 1)
/* We tried to relocate the dll and it failed. */
@@ -344,6 +351,8 @@
load into the same address space. In the "forked" process, the
second DLL always loads into a different location. So, block all
of the memory up to the new load address and try again. */
+ if (fork_debug)
+ system_printf("reserve_upto %p to try to force it to load there",
d->handle);
reserve_upto (d->name, (DWORD) d->handle);
/* Dll *still* loaded in the wrong place. This can happen if it
@@ -352,6 +361,8 @@
preferred address and try again. */
if (i > 0)
{
+ if (fork_debug)
+ system_printf("reserved_at %p to try to force it to load
elsewhere", h);
preferred_block = reserve_at(d->name, (DWORD)h);
}
}
Index: winsup/cygwin/environ.cc
===================================================================
--- winsup.orig/cygwin/environ.cc 2011-04-02 22:26:44.000000000 +0100
+++ winsup/cygwin/environ.cc 2011-04-02 22:28:10.937500000 +0100
@@ -37,6 +37,7 @@
bool reset_com = false;
static bool envcache = true;
static bool create_upcaseenv = false;
+extern bool fork_debug;
static char **lastenviron;
@@ -605,6 +606,7 @@
{"tty", {NULL}, set_process_state, NULL, {{0}, {PID_USETTY}}},
{"upcaseenv", {&create_upcaseenv}, justset, NULL, {{false}, {true}}},
{"winsymlinks", {&allow_winsymlinks}, justset, NULL, {{false}, {true}}},
+ {"forkdebug", {&fork_debug}, justset, NULL, {{false}, {true}}},
{NULL, {0}, justset, 0, {{0}, {0}}}
};
