linux-kernel - Re: [PATCH 1/2] lockdep: add lockdep_assert_not

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Message-ID: <c9293180-3eba-a5f3-b34e-b44ebdd60077@linuxfoundation.org>
Date:   Mon, 22 Feb 2021 13:51:57 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Johannes Berg <johannes@...solutions.net>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, will@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 1/2] lockdep: add lockdep_assert_not_held()

On 2/15/21 9:10 AM, Johannes Berg wrote:
> On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote:
>> On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote:
>>> On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote:
>>>> I think something like so will work, but please double check.
>>>
>>> Yeah, that looks better.
>>>
>>>> +++ b/include/linux/lockdep.h
>>>> @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
>>>>   
>>>>   #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
>>>>   
>>>> -#define lockdep_assert_held(l)	do {				\
>>>> -		WARN_ON(debug_locks && !lockdep_is_held(l));	\
>>>> +#define lockdep_assert_held(l)	do {					\
>>>> +		WARN_ON(debug_locks && lockdep_is_held(l) == 0));	\
>>>>   	} while (0)
>>>
>>> That doesn't really need to change? It's the same.
>>
>> Correct, but I found it more symmetric vs the not implementation below.
> 
> Fair enough. One might argue that you should have an
> 
> enum lockdep_lock_state {
> 	LOCK_STATE_NOT_HELD, /* 0 now */
> 	LOCK_STATE_HELD, /* 1 now */
> 	LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */
> };
> 
> :)
> 


Thank you both. Picking this back up. Will send v2 incorporating
your comments and suggestions.

thanks,
-- Shuah