Messages in this thread Patch in this message | | | From | Andrea Parri <> | Subject | [PATCH] Documentation/locking: Document the semantics of spin_is_locked() | Date | Wed, 28 Feb 2018 11:39:32 +0100 |
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There appeared to be a certain, recurrent uncertainty concerning the semantics of spin_is_locked(), likely a consequence of the fact that this semantics remains undocumented or that it has been historically linked to the (likewise unclear) semantics of spin_unlock_wait().
Document this semantics.
Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Will Deacon <will.deacon@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Akira Yokosawa <akiyks@gmail.com> --- include/linux/spinlock.h | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 4894d322d2584..2639fdc9a916c 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -380,6 +380,17 @@ static __always_inline int spin_trylock_irq(spinlock_t *lock) raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ }) +/** + * spin_is_locked() - Check whether a spinlock is locked. + * @lock: Pointer to the spinlock. + * + * This function is NOT required to provide any memory ordering + * guarantees; it could be used for debugging purposes or, when + * additional synchronization is needed, accompanied with other + * constructs (memory barriers) enforcing the synchronization. + * + * Return: 1, if @lock is (found to be) locked; 0, otherwise. + */ static __always_inline int spin_is_locked(spinlock_t *lock) { return raw_spin_is_locked(&lock->rlock); -- 2.7.4
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