Hello, Christoph. On Mon, Jan 30, 2012 at 11:52:23AM -0600, Christoph Lameter wrote: > We have two possibilities now: > > 1. We say that the value returned from the per cpu allocator is an opaque > value. > > This means that we have to remove the NULL check from the free > function. And audit the kernel code for all occurrences where > a per cpu pointer value of NULL is assumed to mean that no per > cpu allocation has occurred.
No, NULL is never gonna be a valid return from any allocator including percpu. Percpu allocator doesn't and will never do so. > 2. We say that there are special values for the per cpu pointers (NULL, > ZERO_SIZE_PTR) > > Then we would have to guarantee that the per cpu allocator never > returns those values. > > Plus then the ZERO_SIZE_PTR patch will be fine. > > The danger exist of these values being passed as > parameters to functions that do not support them (per_cpu_ptr > etc). Those would need VM_BUG_ONs or some other checks to detect > potential problems. I'm saying we don't have this for ZERO_SIZE_PTR in any meaningful way at this point. If somebody wants to implement it properly, please feel free to, but simply applying ZERO_SIZE_PTR without other changes doesn't make any sense. Thanks. -- tejun _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
