On Mon, 21 Jun 2010, Christoph Lameter wrote: > > > You cannot do that here because this function is also used later when the > > > slab is up. There is more in the percpu allocator which we are also trying > > > to use to avoid having static kmem_cache_cpu declarations. GFP_KERNEL > > > needs to be usable during early boot otherwise functions will have to add > > > special casing for boot situations. > > > > > > > The gfp_allowed_mask only changes once irqs are enabled, so either the > > gfpflags need to be passed into init_kmem_cache_nodes again or we need to > > do something like > > > > gfp_t gfpflags = irqs_disabled() ? GFP_NOWAIT : GFP_KERNEL; > > > > locally. > > What a mess.... > > > The cleanest solution would probably be to extend slab_state to be set in > > kmem_cache_init_late() to determine when we're fully initialized, though. > > Not sure what the point would be. Changing slab_state does not change the > interrupt enabled/disabled state of the processor. > If you added an even higher slab_state level than UP and set it in kmem_cache_init_late(), then you could check for it to determine GFP_NOWAIT or GFP_KERNEL in init_kmem_cache_nodes() rather than irqs_disabled() because that's the only real event that requires kmem_cache_init_late() to need to exist in the first place. I'm not sure if you'd ever use that state again, but it's robust if anything is ever added in the space between kmem_cache_init() and kmem_cache_init_late() for a reason. slab_is_available() certainly doesn't need it because we don't kmem_cache_create() in between the two. When you consider those solutions, it doesn't appear as though removing the gfp_t formal in init_kmem_cache_nodes() is really that much of a cleanup. > Is gfp_allowed_mask properly updated during boot? Then we could just use > > GFP_KERNEL & gfp_allowed_mask > > in these locations? Still bad since we are wasting code on correctness > checks. > That certainly does get us GFP_NOWAIT (same as GFP_BOOT_MASK) before irqs are enabled and GFP_KERNEL afterwards since gfp_allowed_mask is updated at the same time. If it's worth getting of the gfp_t formal in init_kmem_cache_nodes() so much, then that masking would deserve a big fat comment :) > Noone thought about this when designing these checks? The checks cannot be > fixed up to consider boot time so that we do not have to do artistics in > the code? > I think gfp_allowed_mask is the intended solution since it simply masks off GFP_KERNEL and turns those allocations into GFP_BOOT_MASK before it gets updated. -- 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>