On Tue, 2014-09-16 at 17:16 -0700, 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.
Ah, I remember you had this one in your queue for some time :) > However, a subsequent patch was added such that we directly > check for sem->count == RWSEM_WAITING_BIAS right before trying > that cmpxchg(). Thus, commit 9b0fc9c09f1b now just adds overhead. > This patch modifies it so that we only do a check for if > count == RWSEM_WAITING_BIAS. > > Also, add a comment on why we do an "extra check" of count > before the cmpxchg(). heh, so people don't try to remove the "redundant" check! > Cc: Peter Hurley <[email protected]> > Cc: Tim Chen <[email protected]> Acked-by: Davidlohr Bueso <[email protected]> > Signed-off-by: Jason Low <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
