On 10/05/2017 11:49 AM, Kees Cook wrote: > On Thu, Oct 5, 2017 at 7:56 AM, Jens Axboe <[email protected]> wrote: >> On 10/04/2017 06:49 PM, Kees Cook wrote: >>> In preparation for unconditionally passing the struct timer_list pointer to >>> all timer callbacks, switch to using the new timer_setup() and from_timer() >>> to pass the timer pointer explicitly. >>> >>> Cc: Jens Axboe <[email protected]> >>> Cc: Michal Hocko <[email protected]> >>> Cc: Andrew Morton <[email protected]> >>> Cc: Jan Kara <[email protected]> >>> Cc: Johannes Weiner <[email protected]> >>> Cc: Nicholas Piggin <[email protected]> >>> Cc: Vladimir Davydov <[email protected]> >>> Cc: Matthew Wilcox <[email protected]> >>> Cc: Jeff Layton <[email protected]> >>> Cc: [email protected] >>> Cc: [email protected] >>> Cc: Thomas Gleixner <[email protected]> >>> Signed-off-by: Kees Cook <[email protected]> >>> --- >>> This requires commit 686fef928bba ("timer: Prepare to change timer >>> callback argument type") in v4.14-rc3, but should be otherwise >>> stand-alone. >> >> My only complaint about this is the use of a from_timer() macro instead >> of just using container_of() at the call sites to actually show that is >> happening. I'm generally opposed to obfuscation like that. It just means >> you have to look up what is going on, instead of it being readily >> apparent to the reader/reviewer. > > Yeah, this got discussed a bit with tglx and hch. Ultimately, this > seems to be the least bad of several options. Specifically with regard > to container_of(), it just gets to be huge, and makes things harder to > read (almost always requires a line break, needlessly repeats the > variable type definition, etc). Since there is precedent of both using > wrappers on container_of() and for adding from_foo() helpers, I chose > the resulting from_timer().
It might make for a longer line, but at least it's a readable line. What does from_timer() do? Nobody knows, you have to find it and check. So I'd still argue that it's a hell of a lot more readable than some random function name. >> I guess I do have a a second complaint as well - that it landed in -rc3, >> which is rather late considering subsystem trees are usually forked >> earlier than that. Had this been in -rc1, I would have had an easier >> time applying the block bits for 4.15. > > Yes, totally true. tglx and I ended up meeting face-to-face at the > Kernel Recipes conference and we solved some outstanding design issues > with the conversion. The timing meant the new API went into -rc3, > which seemed better than missing an entire release cycle, or carrying > deltas against maintainer trees that would drift. (This is actually my > second massive refactoring of these changes...) Honestly, I think the change should have waited for 4.15 in that case. Why the rush? It wasn't ready for the merge window. > If you don't want to deal with the -rc3 issue, would you want these > changes to get carried in the timer tree instead? I can carry them, not a problem. Just a bit grumpy as this seems poorly handled. -- Jens Axboe
