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

[Linus Torvalds <torvalds@linux-foundation.org>]

On Wed, 13 Aug 2008, Andrew Morton wrote:
> - * in interrupt context :)
> + * Return true if we acquired the lock
>   */
> -static int kexec_lock;
> +static inline bool kexec_trylock(void)
> +{
> +	return !test_and_set_bit(0, &kexec_bitlock);

Nope. That needs to be an "unsigned long".

But more importantl, why not just make it a lock in the first place?

	static DEFINE_SPINLOCK(kexec_lock);

	#define kexec_trylock() spin_trylock(&kexec_lock)
	#define kexec_unlock() spin_unlock(&kexec_lock)

and then you get it all right and clear and obvious.

Yeah, and I didn't check whether there is anything that is supposed to be 
able to sleep. If there is, use a mutex instead of a spinlock, of course.

		Linus