Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 75a7ea0c authored by Will Deacon's avatar Will Deacon Committed by Gerrit - the friendly Code Review server
Browse files

locking/atomic: Add atomic_cond_read_acquire() 



smp_cond_load_acquire() provides a way to spin on a variable with acquire
semantics until some conditional expression involving the variable is
satisfied. Architectures such as arm64 can potentially enter a low-power
state, waking up only when the value of the variable changes, which
reduces the system impact of tight polling loops.

This patch makes the same interface available to users of atomic_t,
atomic64_t and atomic_long_t, rather than require messy accesses to the
structure internals.

Change-Id: I5ef2f84dfe810b4e4d26bbb0617c2070f4ccb678
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Jeremy.Linton@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1507810851-306-3-git-send-email-will.deacon@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Git-commit: 4df714be4dcf40bfb0d4af0f851a6e1977afa02e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: default avatarPrasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: default avatarMukesh Ojha <mojha@codeaurora.org>
parent 22a84c5b

include/asm-generic/atomic-long.h

+3 −0
Original line number Diff line number Diff line
@@ -243,4 +243,7 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u) 
#define atomic_long_inc_not_zero(l) \

	ATOMIC_LONG_PFX(_inc_not_zero)((ATOMIC_LONG_PFX(_t) *)(l))



#define atomic_long_cond_read_acquire(v, c) \

	ATOMIC_LONG_PFX(_cond_read_acquire)((ATOMIC_LONG_PFX(_t) *)(v), (c))



#endif  /*  _ASM_GENERIC_ATOMIC_LONG_H  */

include/linux/atomic.h

+4 −0
Original line number Diff line number Diff line
@@ -627,6 +627,8 @@ static inline int atomic_dec_if_positive(atomic_t *v) 
}

#endif



#define atomic_cond_read_acquire(v, c)	smp_cond_load_acquire(&(v)->counter, (c))



#ifdef CONFIG_GENERIC_ATOMIC64

#include <asm-generic/atomic64.h>

#endif
@@ -1023,6 +1025,8 @@ static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v 
}

#endif



#define atomic64_cond_read_acquire(v, c)	smp_cond_load_acquire(&(v)->counter, (c))



#include <asm-generic/atomic-long.h>



#endif /* _LINUX_ATOMIC_H */