linux-kernel - Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard code value

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Date:   Tue, 30 Jul 2019 18:10:49 +0530
From:   Mukesh Ojha <mojha@...eaurora.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, will@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] locking/mutex: Use mutex flags macro instead of hard
 code value


On 7/30/2019 1:33 PM, Peter Zijlstra wrote:
> On Tue, Jul 30, 2019 at 01:23:13PM +0530, Mukesh Ojha wrote:
>> On 7/29/2019 4:37 PM, Peter Zijlstra wrote:
>>> On Mon, Jul 29, 2019 at 04:22:58PM +0530, Mukesh Ojha wrote:
>>>> Let's use the mutex flag macro(which got moved from mutex.c
>>>> to linux/mutex.h in the last patch) instead of hard code
>>>> value which was used in __mutex_owner().
>>>>
>>>> Signed-off-by: Mukesh Ojha <mojha@...eaurora.org>
>>>> ---
>>>>    include/linux/mutex.h | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
>>>> index 79b28be..c3833ba 100644
>>>> --- a/include/linux/mutex.h
>>>> +++ b/include/linux/mutex.h
>>>> @@ -87,7 +87,7 @@ struct mutex {
>>>>     */
>>>>    static inline struct task_struct *__mutex_owner(struct mutex *lock)
>>>>    {
>>>> -	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);
>>>> +	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
>>>>    }
>>> I would _much_ rather move __mutex_owner() out of line, you're exposing
>>> far too much stuff.
>> if i understand you correctly, you want me to move __mutex_owner() to
>> mutex.c
>> __mutex_owner() is used in mutex_is_locked() and mutex_trylock_recursive
>> inside linux/mutex.h.
>>
>> Shall i move them as well ?
> Yes, then you can make __mutex_owner() static.

To make it static , i have to export mutex_is_locked() after moving it 
inside mutex.c, so that other module can use it.

Also are we thinking of removing
static inline /* __deprecated */ __must_check enum 
mutex_trylock_recursive_enum
mutex_trylock_recursive(struct mutex *lock)

inside linux/mutex.h in future ?

As i see it is used at one or two places and there is a check inside 
checkpatch guarding its further use .

Thanks,
Mukesh


>
> Thanks!