Re: [PATCH 01/17] locking/lockdep: Add lock type enum to explicitly specify read or write locks
From: Yuyang Du
Date: Mon May 13 2019 - 21:34:06 EST
Thanks for review.
On Mon, 13 May 2019 at 19:45, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, May 13, 2019 at 05:11:47PM +0800, Yuyang Du wrote:
> > + * Note that we have an assumption that a lock class cannot ever be both
> > + * read and recursive-read.
> We have such locks in the kernel... see:
> And yes, that is somewhat unfortunate, but hard to get rid of due to
> hysterical raisins.
That is ok, then LOCK_TYPE_RECURSIVE has to be 3 such that
LOCK_TYPE_RECURSIVE & LOCK_TYPE_READ != 0. I thought to do this in the
first place without assuming. Anyway, it is better to know.
And I guess in a task:
recursive_read(x); /* this is ok ? */
read(x) /* not ok ? */
Either way, very small change may need to be made.