DO NOT REPLY [Bug 48535] Potential data race on allocator->max_index in allocator_alloc()

[bu...@apache.org]

https://issues.apache.org/bugzilla/show_bug.cgi?id=48535

--- Comment #5 from sr-dev@gmx.net 2010-09-04 14:17:44 EDT ---
(In reply to comment #1)
> Isn't this an intentional race condition, following the usual pattern
> 
> make a very cheap but imperfect state check
> if it looks good so far:
>   get mutex
>   check state carefully this time, handle appropriately
>   release mutex

Thats true, but the current code does not do this (check again carefully).
Currently it does the following:

if index <= allocator->max_index
   get mutex
   do something1
   release mutex
else
   do something2

But it does not check the state carefully again... So I think it should do
this:

if index <= allocator->max_index
   get mutex
   // max_index could be changed in the mean while
   if index <= allocator->max_index
      do something1
      release mutex
   else
      release mutex
      do something2
else
   do something2

However, I do not know the allocator code at all. But without the second if it
is possible to execute do something1 even if index is greater than max_index!

Regards,
Stefan (reporter of the issue on the mailing list ;-)

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