On Tue, Nov 05, 2013 at 11:13:11PM +0000, Kirill A. Shutemov wrote: > On Tue, Nov 05, 2013 at 03:56:19PM -0800, Andrew Morton wrote: > > On Wed, 6 Nov 2013 00:42:17 +0200 "Kirill A. Shutemov" > > <[email protected]> wrote: > > > > > > > #if USE_SPLIT_PTE_PTLOCKS > > > > > +struct kmem_cache *page_ptl_cachep; > > > > > +void __init ptlock_cache_init(void) > > > > > +{ > > > > > + if (sizeof(spinlock_t) > sizeof(long)) > > > > > + page_ptl_cachep = kmem_cache_create("page->ptl", > > > > > + sizeof(spinlock_t), 0, SLAB_PANIC, > > > > > NULL); > > > > > +} > > > > > > > > Confused. If (sizeof(spinlock_t) > sizeof(long)) happens to be false > > > > then the kernel will later crash. It would be better to use > > > > BUILD_BUG_ON() > > > > here, if that works. Otherwise BUG_ON. > > > > > > if (sizeof(spinlock_t) > sizeof(long)) is false, we don't need dynamicly > > > allocate page->ptl. It's embedded to struct page itself. __ptlock_alloc() > > > never called in this case. > > > > OK. Please add a comment explaining this so the next reader doesn't get > > tripped up like I was. > > Okay, I will tomorrow. > > > Really the function shouldn't exist in this case. It is __init so the > > sin is not terrible, but can this be arranged? > > I would like to get rid of __ptlock_alloc()/__ptlock_free() too, but I > don't see a way within C: we need to know sizeof(spinlock_t) on > preprocessor stage.
FWIW: if the architecture selects ARCH_USE_CMPXCHG_LOCKREF, then a spinlock_t is 32-bit (assuming that unsigned int is also 32-bit). Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
