Messages in this thread | | | Date | Sun, 22 May 2016 21:50:40 +0300 | From | Alexey Dobriyan <> | Subject | Re: [PATCH] seqlock: fix raw_read_seqcount_latch() |
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On Sun, May 22, 2016 at 12:48:27PM +0200, Peter Zijlstra wrote: > On Sat, May 21, 2016 at 11:14:49PM +0300, Alexey Dobriyan wrote: > > lockless_dereference() is supposed to take pointer not integer. > > Urgh :/ > > Is there any way we can make lockless_dereference() issue a warning if > we don't feed it a pointer? > > Would something like so work? All pointer types should silently cast to > void * while integer (and others) should refuse to.
This works (and spammy enough in case of seqlock, which is good) but not for "unsigned long":
include/linux/percpu-refcount.h:146:36: warning: initialization makes pointer from integer without a cast [-Wint-conversion] percpu_ptr = lockless_dereference(ref->percpu_count_ptr);
> --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -544,6 +544,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > */ > #define lockless_dereference(p) \ > ({ \ > + __maybe_unused void * _________p2 = p; \ > typeof(p) _________p1 = READ_ONCE(p); \ > smp_read_barrier_depends(); /* Dependency order vs. p above. */ \ > (_________p1); \
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