Messages in this thread Patch in this message |  | | Date | Mon, 3 Feb 2020 16:09:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH -v2 5/7] locking/percpu-rwsem: Remove the embedded rwsem |
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On Mon, Feb 03, 2020 at 06:20:50AM -0800, Christoph Hellwig wrote: > On Fri, Jan 31, 2020 at 04:07:08PM +0100, Peter Zijlstra wrote: > > @@ -53,12 +53,6 @@ struct rw_semaphore { > > #endif > > }; > > > > -/* > > - * Setting all bits of the owner field except bit 0 will indicate > > - * that the rwsem is writer-owned with an unknown owner. > > - */ > > -#define RWSEM_OWNER_UNKNOWN (-2L) > > Can you split the removal of the non-owned resem support into a separate > patch? I still think keeping this one and moving aio to that scheme is > a better idea than the current ad-hoc locking scheme that has all kinds > of issues.
That's basically 2 lines of code and a comment, surely we can ressurect that if/when it's needed again?
--- diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 00d6054687dd..8a418d9eeb7a 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -53,12 +53,6 @@ struct rw_semaphore { #endif }; -/* - * Setting all bits of the owner field except bit 0 will indicate - * that the rwsem is writer-owned with an unknown owner. - */ -#define RWSEM_OWNER_UNKNOWN (-2L) - /* In all implementations count != 0 means locked */ static inline int rwsem_is_locked(struct rw_semaphore *sem) { diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 44e68761f432..5449ab33f89e 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -660,8 +659,6 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem, unsigned long flags; bool ret = true; - BUILD_BUG_ON(!(RWSEM_OWNER_UNKNOWN & RWSEM_NONSPINNABLE)); - if (need_resched()) { lockevent_inc(rwsem_opt_fail); return false;
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