Re: [patch 1/3] spinlock fix #1, *_can_lock() primitives

* Linus Torvalds <torvalds@osdl.org> wrote:

> On Thu, 20 Jan 2005, Ingo Molnar wrote:
> > 
> > You are right about UP, and the patch below adds the UP variants. It's
> > analogous to the existing wrapping concept that UP 'spinlocks' are
> > always unlocked on UP. (spin_can_lock() is already properly defined on
> > UP too.)
> 
> Looking closer, it _looks_ like the spinlock debug case never had a
> "spin_is_locked()" define at all. Or am I blind? Maybe UP doesn't
> want/need it after all?

i remember frequently breaking the UP build wrt. spin_is_locked() when
redoing all the spinlock primitives for PREEMPT_RT.

looking closer, here's the debug variant it appears:

 /* without debugging, spin_is_locked on UP always says
  * FALSE. --> printk if already locked. */
 #define spin_is_locked(x) \
	({ \
	 	CHECK_LOCK(x); \
		if ((x)->lock&&(x)->babble) { \
			(x)->babble--; \
			printk("%s:%d: spin_is_locked(%s:%p) already locked by %s/%d\n", \
					__FILE__,__LINE__, (x)->module, \
					(x), (x)->owner, (x)->oline); \
		} \
		0; \
	})

(the comment is misleading a bit, this _is_ the debug branch. The
nondebug branch has a spin_is_locked() definition too.)

	Ingo
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