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From: Thomas Gleixner <tglx@linutronix.de>
To: Wander Lairson Costa <wander@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"open list:LOCKING PRIMITIVES" <linux-kernel@vger.kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH] rtmutex: ensure we wake up the top waiter
Date: Thu, 02 Feb 2023 08:48:48 +0100	[thread overview]
Message-ID: <87k010zevz.ffs@tglx> (raw)
In-Reply-To: <20230131175350.s7eiz55fozlhaegh@fedora>

On Tue, Jan 31 2023 at 14:53, Wander Lairson Costa wrote:
> On Tue, Jan 31, 2023 at 02:46:19PM -0300, Wander Lairson Costa wrote:
>> > If you have traces which show the sequence of lock events leading to
>> > this problem, then you should be able to decode the scenario. If you
>> > fail to extract the information, then please provide the traces so we
>> > can stare at them.
>> >
>> 
>> Here we go:
>> 
>> Let L1 and L2 be two spinlocks.
>> 
>> Let T1 be a task holding L1 and blocked on L2. T1, currently, is the top
>> waiter of L2.
>> 
>> Let T2 be the task holding L2.
>> 
>> Let T3 be a task trying to acquire L1.
>> 
>> The following events will lead to a state in which the wait queue of L2
>> isn't empty but nobody holds it.

That explains it nicely. Care to resend with proper explanations in the
changelog?

Thanks,

        tglx

  reply	other threads:[~2023-02-02  8:07 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-17 17:26 [PATCH] rtmutex: ensure we wake up the top waiter Wander Lairson Costa
2023-01-17 19:32 ` Waiman Long
2023-01-17 19:40   ` Waiman Long
2023-01-17 20:01     ` Wander Lairson Costa
2023-01-17 20:00   ` Wander Lairson Costa
2023-01-18  0:05 ` Thomas Gleixner
2023-01-18 18:49   ` Wander Lairson Costa
2023-01-19 20:53     ` Thomas Gleixner
2023-01-31 17:46       ` Wander Lairson Costa
2023-01-31 17:53         ` Wander Lairson Costa
2023-02-02  7:48           ` Thomas Gleixner [this message]
2023-02-02 11:20             ` Wander Lairson Costa
2023-02-06 14:12 ` [tip: locking/urgent] rtmutex: Ensure that the top waiter is always woken up tip-bot2 for Wander Lairson Costa

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