locking/rwsem: Clarify that RWSEM_READER_OWNED is just a hint
Clarify in the comments that the RWSEM_READER_OWNED bit in the owner field is just a hint, not an authoritative state of the rwsem. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Link: https://lore.kernel.org/r/20240222150540.79981-4-longman@redhat.com
This commit is contained in:
parent
d6cac0b6b0
commit
d566c78659
|
@ -35,7 +35,7 @@
|
||||||
/*
|
/*
|
||||||
* The least significant 2 bits of the owner value has the following
|
* The least significant 2 bits of the owner value has the following
|
||||||
* meanings when set.
|
* meanings when set.
|
||||||
* - Bit 0: RWSEM_READER_OWNED - The rwsem is owned by readers
|
* - Bit 0: RWSEM_READER_OWNED - rwsem may be owned by readers (just a hint)
|
||||||
* - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock
|
* - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock
|
||||||
*
|
*
|
||||||
* When the rwsem is reader-owned and a spinning writer has timed out,
|
* When the rwsem is reader-owned and a spinning writer has timed out,
|
||||||
|
@ -1002,8 +1002,8 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* To prevent a constant stream of readers from starving a sleeping
|
* To prevent a constant stream of readers from starving a sleeping
|
||||||
* waiter, don't attempt optimistic lock stealing if the lock is
|
* writer, don't attempt optimistic lock stealing if the lock is
|
||||||
* currently owned by readers.
|
* very likely owned by readers.
|
||||||
*/
|
*/
|
||||||
if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
|
if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
|
||||||
(rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))
|
(rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))
|
||||||
|
|
Loading…
Reference in New Issue