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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Will Deacon <will@kernel.org>
Cc:     Mel Gorman <mgorman@techsingularity.net>,
        Peter Zijlstra <peterz@infradead.org>, Jan Kara <jack@suse.cz>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Pierre Gondois <pierre.gondois@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-RT <linux-rt-users@vger.kernel.org>
Subject: Re: [PATCH] rtmutex: Add acquire semantics for rtmutex lock
 acquisition
Message-ID: <Y5yavm77lWLH+IWj@linutronix.de>
References: <20221202100223.6mevpbl7i6x5udfd@techsingularity.net>
 <Y4nfopZfBxR4lJ6G@linutronix.de>
 <20221202150158.xzgovoy7wuic6vvk@techsingularity.net>
 <20221216111412.GA8666@willie-the-truck>
 <20221216135548.itw2xrqbvuldk35y@techsingularity.net>
 <20221216155803.GB8949@willie-the-truck>
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On 2022-12-16 15:58:04 [+0000], Will Deacon wrote:
> I guess bigeasy can give the weaker barrier a try if he has the time, but
> otherwise we can leave the change as-is.

I can't give a try because I have no HW. All I contributed here so far
was based on what you wrote in the previous email and then I spotted the
lack of the barrier of any sorts and asked about it.
I _would_ assume that the cmpxchg_barrier() here would work but I'm far
from knowing.
If the explicit barrier after the cmpxchg_relaxed() is what you two
agree on and it is better/ cheaper/ more obvious then fine. Do it ;)

> Cheers,
> 
> Will

Sebastian