Mail Archives: cygwin/2012/02/07/17:49:07
On 2012-02-07 17:47, Ryan Johnson wrote:
> On 07/02/2012 11:14 AM, Corinna Vinschen wrote:
>> On Feb 7 16:43, Denis Excoffier wrote:
>>> I've also instrumented cygwin1.dll as suggested recently to Heiko Elger
>>> in http://cygwin.com/ml/cygwin/2012-02/msg00092.html
>>> [...]
>>> - the /proc/<pid>/maps of the processes involved in the fork failure look normal:
>>> ...
>>> 61262000-61470000 rw-p 00262000 C095:C492 13792273859134500 /usr/bin/cygwin1.dll
>>> 674C0000-674C1000 r--p 00000000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 674C1000-674D8000 r-xp 00001000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 674D8000-675B8000 rw-p 00018000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 675B8000-675B9000 r--p 000F8000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 675B9000-675BB000 rw-p 000F9000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 675BB000-675BC000 r--p 000FB000 C095:C492 2251799814315820 /usr/bin/cygiconv-2.dll
>>> 6AFC0000-6AFC1000 r--p 00000000 C095:C492 1407374884189126 /usr/bin/cygreadline7.dll
>>> ...
>> If this is the map of the forked child, then it's not exactly normal.
>> Consider that dll_list::reserve_space tries to reserve the memory which
>> is later supposed to be used for cygiconv-2.dll, but apparently
>> cygiconv-2.dll is already loaded.
>>
>> What your report is missing is a bit more information. We external
>> observes don't know if the error message in reserve_space actually
>> reported the address 0x674C0000, and we also don't know if the parent
>> process has the same layout as the child, or if it's different. The
>> above information alone is not enough to evaluate the situation around
>> cygiconv-2.dll in your scenario.
>>
>>> Now looking into dll_init.cc, i'm probably going to try the following: if
>>> VirtualAlloc (line 429, just before 'already occupied') fails, try it
>>> once more after waiting, say 100ms. Any comments?
>> Don't, it won't help. Assuming my above assumptions are correct (but we
>> need proof), we seem to have a situation like this:
>>
>> - cygiconv-2.dll has been loaded before cygwin1.dll
>>
>> - cygwin1.dll tries to reserve space for later loading of cygiconv-2.dll
>> but cygiconv-2.dll is already where it belongs.
>>
>> - Since rsync is linked against cygiconv-2.dll, I'm wondering
>> why it's in the list of runtime loaded DLLs.
> Denis, could you recompile cygwin1.dll to print out the list of dlls, and their types, on fork failure? IIRC, the list is pretty easy to traverse (singly-linked list rooted in a global variable or something similar). That might confirm or rule out Corinna's hypothesis.
You mean, something like this:
void
dll_list::reserve_space ()
{
for (dll* d = dlls.istart (DLL_LOAD); d; d = dlls.inext ())
#ifdef PRISTINE
if (!VirtualAlloc (d->handle, d->image_size, MEM_RESERVE, PAGE_NOACCESS))
fabort ("address space needed by '%W' (%p) is already occupied",
d->modname, d->handle);
#else
#define TYPE_SHOW(x) ((x) == DLL_NONE) ? "DLL_NONE" : ((x) == DLL_LINK) ? "DLL_LINK" : ((x) == DLL_LOAD) ? "DLL_LOAD" : ((x) == DLL_ANY) ? "DLL_ANY" : "DLL_(unknown)"
if (!VirtualAlloc (d->handle, d->image_size, MEM_RESERVE, PAGE_NOACCESS)) {
#if 0
for (dll* d_alt = dlls.istart (DLL_ANY); d_alt; d_alt = dlls.inext ()) {
system_printf ("address space needed by '%W' (%p with type %d=%s) is perhaps already occupied",
d_alt->modname, d_alt->handle, d_alt->type, TYPE_SHOW(d_alt->type));
};
#else
for (dll* d_alt = dlls.start.next; d_alt; d_alt = d_alt.next ()) {
system_printf ("address space needed by '%W' (%p with type %d=%s) is perhaps already occupied",
d_alt->modname, d_alt->handle, d_alt->type, TYPE_SHOW(d_alt->type));
};
#endif
fabort ("address space needed by '%W' (%p) is already occupied",
d->modname, d->handle);
};
#endif
}
By the way, if someone can explain why in dll_init.h we have
dll *istart (dll_type t)
{
hold_type = t;
hold = &start;
return inext ();
}
and not
dll *istart (dll_type t)
{
hold_type = t;
hold = &start;
return hold;
}
Regards,
Denis Excoffier.
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