From: Peter Zijlstra <peterz@infradead.org>
To: "Xu, Yanfei" <yanfei.xu@windriver.com>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will@kernel.org>, Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] locking/mutex: Reduce chance of setting HANDOFF bit on unlocked mutex
Date: Wed, 30 Jun 2021 16:50:15 +0200 [thread overview]
Message-ID: <YNyEpy+IUtJbWOZS@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <dbd002b9-d266-0f69-1c55-eb4e5d4d6a57@windriver.com>
On Wed, Jun 30, 2021 at 10:43:37PM +0800, Xu, Yanfei wrote:
> > +static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock, bool handoff)
> > {
> > unsigned long owner, curr = (unsigned long)current;
> >
> > owner = atomic_long_read(&lock->owner);
> > for (;;) { /* must loop, can race against a flag */
> > + unsigned long flags = __owner_flags(owner);
> > unsigned long task = owner & ~MUTEX_FLAGS;
> >
> > if (task) {
> > + if (flags & MUTEX_FLAG_PICKUP) {
> >
> > + if (task != curr)
> > + break;
> > +
> > + flags &= ~MUTEX_FLAG_PICKUP;
> > +
>
> Hmm.. Should we also clear HANDOFF bit here? I don't find where it is
> cleared.
Should already be gone; see __mutex_handoff().
prev parent reply other threads:[~2021-06-30 14:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-29 20:11 [PATCH] locking/mutex: Reduce chance of setting HANDOFF bit on unlocked mutex Waiman Long
2021-06-30 10:21 ` Peter Zijlstra
2021-06-30 13:50 ` Waiman Long
2021-06-30 13:56 ` Peter Zijlstra
2021-06-30 14:13 ` Waiman Long
2021-06-30 14:46 ` Peter Zijlstra
2021-06-30 14:43 ` Xu, Yanfei
2021-06-30 14:50 ` Peter Zijlstra [this message]
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