[PATCH 1/3] msvcrt: Lock the heap in _callnewh
piotr.caban at gmail.com
Fri Nov 6 05:11:20 CST 2015
On 11/06/15 11:53, Martin Storsjö wrote:
> On Fri, 6 Nov 2015, Piotr Caban wrote:
>> On 11/06/15 11:28, Martin Storsjo wrote:
>>> int CDECL _callnewh(MSVCRT_size_t size)
>>> + int ret = 0;
>>> + LOCK_HEAP;
>>> - (*MSVCRT_new_handler)(size);
>>> - return 0;
>>> + ret = (*MSVCRT_new_handler)(size);
>>> + UNLOCK_HEAP;
>>> + return ret;
>> It doesn't make sense to lock heap cs in this case. Native is not
>> doing it (at least in case of msvcp90.dll).
> Hmm, but wouldn't it risk a race with another thread doing
> set_new_handler then? OTOH I guess that's ok/expected?
Yes, there's a possibility of race in wine code. It can be easily
avoided by storing new_handler in local variable in callnewh. Then it
will be possible to call old handler while new handler was set. I think
that it's better then possible crash if new_handler is set to NULL.
> But there's a similar lock in MSVCRT_operator_new; should we do the same
> locking on the msvcp side instead then, or just skip it altogether?
I guess that operator_new should use callnewh without locking the heap
section. It can be easily tested by setting new_handler that takes lots
of time to finish and trying to allocate big memory chunks in 2 threads.
If second new_handler is called while first is still executed than
there's no lock in native library (it's not a test that can go into wine
because it depends on allocation failure).
>> The return value change looks almost correct - the function only
>> returns 0 or 1.
> Ok, so should I force the return value to 0 or 1 regardless of what the
> function returns? I.e.
> ret = (*MSVCRT_new_handler)(size) ? 1 : 0;
Yes, this is what native does.
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