Re: [PATCH v2] locking/rwsem: Avoid double checking before try acquiring write lock

On Tue, 2014-09-16 at 16:08 -0400, Peter Hurley wrote: > Hi Jason, > > On 09/16/2014 03:01 PM, Jason Low wrote: > > Commit 9b0fc9c09f1b checks for if there are known active lockers in > > order to avoid write trylocking using expensive cmpxchg() when it > > likely wouldn't get the lock. > > > > H

Re: [PATCH v2] locking/rwsem: Avoid double checking before try acquiring write lock

On Tue, 2014-09-16 at 16:08 -0400, Peter Hurley wrote: > Hi Jason, > > On 09/16/2014 03:01 PM, Jason Low wrote: > > Commit 9b0fc9c09f1b checks for if there are known active lockers in > > order to avoid write trylocking using expensive cmpxchg() when it > > likely wouldn't get the lock. > > > > H

Re: [PATCH v2] locking/rwsem: Avoid double checking before try acquiring write lock

Hi Jason, On 09/16/2014 03:01 PM, Jason Low wrote: > Commit 9b0fc9c09f1b checks for if there are known active lockers in > order to avoid write trylocking using expensive cmpxchg() when it > likely wouldn't get the lock. > > However, a subsequent patch was added such that we directly check for >

[PATCH v2] locking/rwsem: Avoid double checking before try acquiring write lock

Commit 9b0fc9c09f1b checks for if there are known active lockers in order to avoid write trylocking using expensive cmpxchg() when it likely wouldn't get the lock. However, a subsequent patch was added such that we directly check for sem->count == RWSEM_WAITING_BIAS right before trying that cmpxch