Re: [PATCH] kexec jump: fix compiling warning on xchg(&kexec_lock, 0) in kernel_kexec()

Eric W. Biederman
2008-08-13T18:23:48Z

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

> 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