Re: [Xen-devel] [PATCH] spinlock: improve spin_is_locked() for recursive locks

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Thu, Mar 24, 2016 at 4:19 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 24.03.16 at 16:55, <david.vrabel@xxxxxxxxxx> wrote:
>> On 24/03/16 11:30, Jan Beulich wrote:
>>> Recursive locks know their current owner, and since we use the function
>>> solely to determine whether a particular lock is being held by the
>>> current CPU (which so far has been an imprecise check), make actually
>>> check the owner for recusrively acquired locks.
>>
>> What's the expected behaviour of _spin_is_locked() if the lock is held
>> by another CPU?
>>
>> Before it may return true if it is held by another CPU, now it will
>> always return false in this case.
>
> Correct - hence the reference to this only being used for a limited
> set of cases (read: ASSERT()s and alike).

A bunch of the mm locks add "_by_me" at the end of the function.  Did
spin_is_locked() used to have that as well?

In any case I suppose "spin_is_locked_by_someone()" is really pretty
useless information.

 -George

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