[PATCHv4] powerpc: Fix write-after-destroy in lock elision

[Andreas Schwab]

On Jan 11 2017, "Ulrich Weigand" <uweigand@de.ibm.com> wrote:

> Tulio Magno Quites Machado Filho wrote:
>
>> +      /* Update adapt_count in the critical section to prevent a
>> +	 write-after-destroy error as mentioned in BZ 20822.  The
>> +	 following update of adapt_count has to be contained within
>> +	 the critical region of the fall-back lock in order to not violate
>> +	 the mutex destruction requirements.  */
>> +      short __tmp = atomic_load_relaxed (adapt_count);
>> +      if (__tmp > 0)
>> +        atomic_store_relaxed (adapt_count, __tmp--);
>
> Doesn't this have to be --__tmp to have any effect?

It should be just __tmp - 1.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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