[PATCH 6/9] asm-generic/bitops/atomic.h: Rewrite using atomic_fetch_*

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:

quoted

+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.

Will