Messages in this thread | | | Date | Thu, 24 May 2018 14:09:49 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH 6/9] asm-generic/bitops/atomic.h: Rewrite using atomic_fetch_* |
| |
On Thu, May 24, 2018 at 01:47:39PM +0100, Will Deacon wrote: > On Thu, May 24, 2018 at 02:44:10PM +0200, Peter Zijlstra wrote: > > On Thu, May 24, 2018 at 11:59:43AM +0100, Will Deacon wrote: > > > +static inline void set_bit(unsigned int nr, volatile unsigned long *p) > > > { > > > + p += BIT_WORD(nr); > > > + atomic_long_fetch_or_relaxed(BIT_MASK(nr), (atomic_long_t *)p); > > > } > > > > > > +static inline void clear_bit(unsigned int nr, volatile unsigned long *p) > > > { > > > + p += BIT_WORD(nr); > > > + atomic_long_fetch_andnot_relaxed(BIT_MASK(nr), (atomic_long_t *)p); > > > } > > > > > > +static inline void change_bit(unsigned int nr, volatile unsigned long *p) > > > { > > > + p += BIT_WORD(nr); > > > + atomic_long_fetch_xor_relaxed(BIT_MASK(nr), (atomic_long_t *)p); > > > } > > > > Why use the fetch variants here? > > I noticed the same thing just now; I'll drop that and just use the > non-value-returning variants. It's shame that I can't do the same for > the lock.h unlock code, but we don't have non-returning release variants.
As an aside, If I complete the autogeneration stuff, it'll be possible to generate those. I split out the necessary barriers in [1], but I still have a lot of other preparatory cleanup to do.
IIUC, the void-returning atomic ops are relaxed, so trying to unify that with the usual rule that no suffix means fence will slow things down unless we want to do a treewide substitition to fixup for that.
Thanks, Mark.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?h=atomics/api-unification&id=c6b9ff2627d06776e427a7f1a7f83caeff3db536
| |