linux-kernel - RE: [PATCH v2] locking/rtmutex: Fix incorrect spinning condition

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Message-ID: <PH0PR11MB58807AA009DFAAC1789ACDEBDA7B9@PH0PR11MB5880.namprd11.prod.outlook.com>
Date:   Mon, 20 Dec 2021 01:54:19 +0000
From:   "Zhang, Qiang1" <qiang1.zhang@...el.com>
To:     Waiman Long <longman@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "will@...nel.org" <will@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] locking/rtmutex: Fix incorrect spinning condition



> When the lock owner is on CPU and not need resched, the current waiter 
> need to be checked, if it not longer top the waiter, stop spinning.
>
>Incorrect grammar, should be "if it is no longer the top waiter". There is a similar typo in the existing code comment too.
>
>You can modify the subject line to [PATCH-tip ...] to indicate that it is supposed to be apply on top of the tip tree. Other than that, the patch looks good.

Thanks, Longman. I will  modify it and resend.

Thanks,

Zqiang
>
>Cheers,
>Longman

>
> Fixes: c3123c431447 ("locking/rtmutex: Dont dereference waiter 
> lockless")
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> ---
>   v1->v2:
>   Modify description information.
>
>   kernel/locking/rtmutex.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 
> 0c1f2e3f019a..8555c4efe97c 100644
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -1383,7 +1383,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
>   		 *  - the VCPU on which owner runs is preempted
>   		 */
>   		if (!owner_on_cpu(owner) || need_resched() ||
> -		    rt_mutex_waiter_is_top_waiter(lock, waiter)) {
> +		    !rt_mutex_waiter_is_top_waiter(lock, waiter)) {
>   			res = false;
>   			break;
>   		}