On Mon, 2010-06-28 at 02:03 -0700, David Rientjes wrote: > On Mon, 28 Jun 2010, Benjamin Herrenschmidt wrote: > > > Hi folks ! > > > > Internally, I'm hitting a little "nit"... > > > > sysfs_slab_add() has this check: > > > > if (slab_state < SYSFS) > > /* Defer until later */ > > return 0; > > > > But sysfs_slab_remove() doesn't. > > > > So if the slab is created -and- destroyed at, for example, arch_initcall > > time, then we hit a WARN in the kobject code, trying to dispose of a > > non-existing kobject. > > > Indeed, but shouldn't we be appropriately handling the return value of > sysfs_slab_add() so that it fails cache creation? We wouldn't be calling > sysfs_slab_remove() on a cache that was never created. It's eventually created, but yes, we should probably store a state, unless we have a clean way to know the kobject in there is uninitialized and test for that. > > Now, at first sight, just adding the same test to sysfs_slab_remove() > > would do the job... but it all seems very racy to me. > > > > I don't understand in fact how this slab_state deals with races at all. > > > All modifiers of slab_state are intended to be run only on the boot cpu so > the only concern is the ordering. We need slab_state to indicate how far > slab has been initialized since we can't otherwise enforce how code uses > slab in between things like kmem_cache_init(), kmem_cache_init_late(), and > initcalls on the boot cpu. But initcalls aren't pinned to the boot CPU... IE. I don't see how the sysfs creation avoids racing with SLAB creation, or am I missing something ? Cheers, Ben. > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxxx For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>