Messages in this thread |  | | | Date | Fri, 1 Jul 2005 08:57:21 +0200 | | From | Ingo Molnar <> | | Subject | Re: 2.6.13-rc1 CONFIG_DEBUG_SPINLOCK is useless on SMP |
* Keith Owens <kaos@ocs.com.au> wrote:
> 2.6.13-rc1 built with SMP=Y and DEBUG_SPINLOCK=y. That uses > kernel/spinlock.c instead of the inline definitions of the spinlock > functions. Alas only the inline definitions test for > DEBUG_SPINLOCK=y, none of the code in in spinlock.c has any debug > facilities.
the spinlock cleanups in -mm (not yet in -git) obsolete most of the debugging approach of the current kernel.
but even in terms of 2.6.13-rc1, i'm not completely sure what you mean. Yes, there's no debugging code in kernel/spinlock.c because much of the DEBUG_SPINLOCK code (under the old method) is located in the arch spinlock.h files. I.e. on x86 you'll get SMP spinlock debugging from asm-i386/spinlock.h:
static inline void _raw_spin_lock(spinlock_t *lock) { #ifdef CONFIG_DEBUG_SPINLOCK if (unlikely(lock->magic != SPINLOCK_MAGIC)) { printk("eip: %p\n", __builtin_return_address(0)); BUG(); } #endif the only practical exception is when CONFIG_PREEMPT is enabled: the arch level trylock, upon which the PREEMPT spinlocks rely on heavily, has no meaningful DEBUG_SPINLOCK checks. (but PREEMPT has other checks which partly offset this.) In any case, this too is fixed by my spinlock cleanups - there all debugging is done centrally in lib/spinlock_debug.c.
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