From: Thomas Gleixner <tglx@linutronix.de>
To: Zqiang <qiang1.zhang@intel.com>,
peterz@infradead.org, mingo@redhat.com, will@kernel.org,
longman@redhat.com
Cc: linux-kernel@vger.kernel.org, qiang1.zhang@intel.com
Subject: Re: [PATCH v2] locking/rtmutex: Fix incorrect spinning condition
Date: Fri, 17 Dec 2021 21:53:04 +0100 [thread overview]
Message-ID: <87k0g3ar7z.ffs@tglx> (raw)
In-Reply-To: <20211217074207.77425-1-qiang1.zhang@intel.com>
Zqiang,
On Fri, Dec 17 2021 at 15:42, 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.
>
> 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;
good catch!
Though this does not apply because the condition is incomplete. You
somehow dropped this from the condition:
vcpu_is_preempted(task_cpu(owner)))
Please make always sure that your patches apply against Linus tree
before sending them out.
Thanks,
tglx
next prev parent reply other threads:[~2021-12-17 20:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 7:42 [PATCH v2] locking/rtmutex: Fix incorrect spinning condition Zqiang
2021-12-17 20:53 ` Thomas Gleixner [this message]
2021-12-18 7:24 ` Zhang, Qiang1
2021-12-18 9:34 ` Thomas Gleixner
2021-12-20 1:45 ` Zhang, Qiang1
2021-12-18 10:01 ` [tip: locking/core] locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() tip-bot2 for Zqiang
2021-12-19 21:09 ` [PATCH v2] locking/rtmutex: Fix incorrect spinning condition Waiman Long
2021-12-20 1:54 ` Zhang, Qiang1
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