Linus Torvalds <torvalds@linux-foundation.org> writes:

quoted text
> On Wed, 13 Aug 2008, Huang Ying wrote:
>>
>> -	xchg(&kexec_lock, 0);
>> +	locked = xchg(&kexec_lock, 0);
>> +	BUG_ON(!locked);
>
> Why do you want to do this at all? 
>
> And why do you implement your locks with xchg() in the first place? That's 
> total and utter crap.
>
> Hint: we have _real_ locking primitives in the kernel.

This part certainly.

The way the code should work, and the way it has in the past is:
image = xchg(&kexec_image, NULL)
if (!image)
   return -EINVAL;

Very simple and very obvious and very easy to get right, and it has
been that way for years.

Eric
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