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atomics/treewide: Make atomic_fetch_add_unless() optional

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Several architectures these have a near-identical implementation based
on atomic_read() and atomic_cmpxchg() which we can instead define in
<linux/atomic.h>, so let's do so, using something close to the existing
x86 implementation with try_cmpxchg().

Where an architecture provides its own atomic_fetch_add_unless(), it
must define a preprocessor symbol for it. The instrumented atomics are
updated accordingly.

Note that arch/arc's existing atomic_fetch_add_unless() had redundant
barriers, as these are already present in its atomic_cmpxchg()
implementation.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Palmer Dabbelt <palmer@sifive.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Link: https://lore.kernel.org/lkml/20180621121321.4761-7-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mark Rutland
2018-06-21 13:13:09 +01:00
committed by Ingo Molnar
parent bef828204a
commit eccc2da8c0
21 changed files with 34 additions and 231 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/sparc/include/asm/atomic_32.h
View File

@@ -30,6 +30,8 @@ int atomic_xchg(atomic_t *, int);
int atomic_fetch_add_unless(atomic_t *, int, int);
void atomic_set(atomic_t *, int);
#define atomic_fetch_add_unless atomic_fetch_add_unless
#define atomic_set_release(v, i) atomic_set((v), (i))
#define atomic_read(v) READ_ONCE((v)->counter)

15
arch/sparc/include/asm/atomic_64.h
View File

@@ -89,21 +89,6 @@ static inline int atomic_xchg(atomic_t *v, int new)
return xchg(&v->counter, new);
}
static inline int atomic_fetch_add_unless(atomic_t *v, int a, int u)
{
int c, old;
c = atomic_read(v);
for (;;) {
if (unlikely(c == (u)))
break;
old = atomic_cmpxchg((v), c, c + (a));
if (likely(old == c))
break;
c = old;
}
return c;
}
#define atomic64_cmpxchg(v, o, n) \
((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))