Re: [PATCH v3 2/2] locking/percpu-rwsem: Annotate rwsem ownership transfer by setting RWSEM_OWNER_UNKNOWN

From: Waiman Long
Date: Tue May 15 2018 - 14:02:08 EST

On 05/15/2018 01:58 PM, Peter Zijlstra wrote:
> On Tue, May 15, 2018 at 01:38:04PM -0400, Waiman Long wrote:
>> +/*
>> + * Owner value to indicate the rwsem's owner is not currently known.
>> + */
>> +#define RWSEM_OWNER_UNKNOWN ((struct task_struct *)-1)
> It might be nice to comment that this works and relies on having that
> ANON_OWNER bit set.

I am just trying not to expose internal working of rwsem, but I can
document that one of the bits is the real deal without specifying which one.