On Thu, 2009-06-18 at 16:30 -0400, Geoff Thorpe wrote: > I've left the volatile qualifier in the generated API because I didn't > feel so comfortable changing APIs, but I also added the "memory" clobber > for all cases - whereas it seems the existing set_bits(), clear_bits(), > [...] functions didn't declare this... Do you see any issue with having > the 'volatile' in the prototype as well as the clobber in the asm? > > Actually, might as well just respond to the new patch instead... :-) Thx.
I think the story with the memory clobber is that it depends whether we consider the functions as ordering accesses or not (ie, can potentially be used with lock/unlock semantics). The general rule is that those who don't return anything don't need to have those semantics, and thus could only be advertised as clobbering p[word] -but- there are issues there. For example, despite the (relatively new) official _lock/_unlock variants, there's still code that abuses constructs like test_and_set_bit/clear_bit as locks and in that case, clear bits needs a clobber. So I would say at this stage better safe than having to track down incredibly hard to find bugs, and let's make them all take that clobber. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
