Message-ID: <71c5ca50-1bf9-4ef7-eea0-634f66838d4a@redhat.com>
Date:   Sun, 19 Dec 2021 16:09:20 -0500
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Subject: Re: [PATCH v2] locking/rtmutex: Fix incorrect spinning condition
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To:     Zqiang <qiang1.zhang@intel.com>, peterz@infradead.org,
        mingo@redhat.com, will@kernel.org
Cc:     linux-kernel@vger.kernel.org
References: <20211217074207.77425-1-qiang1.zhang@intel.com>
From:   Waiman Long <longman@redhat.com>
In-Reply-To: <20211217074207.77425-1-qiang1.zhang@intel.com>
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Precedence: bulk

On 12/17/21 02:42, Zqiang wrote:
> 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.

Cheers,
Longman

>
> Fixes: c3123c431447 ("locking/rtmutex: Dont dereference waiter lockless")
> Signed-off-by: Zqiang <qiang1.zhang@intel.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;
>   		}