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From: Andy Lutomirski <luto@kernel.org>
To: LKML <linux-kernel@vger.kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Sasha Levin <sashal@kernel.org>
Cc: linux-tip-commits@vger.kernel.org,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	stable <stable@vger.kernel.org>, X86 ML <x86@kernel.org>
Subject: Re: [tip: x86/urgent] membarrier: Add an actual barrier before rseq_preempt()
Date: Mon, 14 Dec 2020 10:05:18 -0800	[thread overview]
Message-ID: <CALCETrW4KAbvAE45T4N0CMdR7XQyrRQTEAq5fX=xVpGAEb3KwA@mail.gmail.com> (raw)
In-Reply-To: <160750336770.3364.7388742360472960633.tip-bot2@tip-bot2>

On Wed, Dec 9, 2020 at 12:42 AM tip-bot2 for Andy Lutomirski
<tip-bot2@linutronix.de> wrote:
>
> The following commit has been merged into the x86/urgent branch of tip:
>
> Commit-ID:     2ecedd7569080fd05c1a457e8af2165afecfa29f
> Gitweb:        https://git.kernel.org/tip/2ecedd7569080fd05c1a457e8af2165afecfa29f
> Author:        Andy Lutomirski <luto@kernel.org>
> AuthorDate:    Thu, 03 Dec 2020 21:07:04 -08:00
> Committer:     Thomas Gleixner <tglx@linutronix.de>
> CommitterDate: Wed, 09 Dec 2020 09:37:43 +01:00
>
> membarrier: Add an actual barrier before rseq_preempt()
>
> It seems that most RSEQ membarrier users will expect any stores done before
> the membarrier() syscall to be visible to the target task(s).  While this
> is extremely likely to be true in practice, nothing actually guarantees it
> by a strict reading of the x86 manuals.  Rather than providing this
> guarantee by accident and potentially causing a problem down the road, just
> add an explicit barrier.
>
> Fixes: 70216e18e519 ("membarrier: Provide core serializing command, *_SYNC_CORE")

Whoops, this got mangled on its way to tip.  This should be:

Fixes: 2a36ab717e8f ("rseq/membarrier: Add
MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ")

and this patch does not need to be backported.

  reply	other threads:[~2020-12-14 18:06 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-04  5:07 [PATCH v3 0/4] membarrier fixes Andy Lutomirski
2020-12-04  5:07 ` [PATCH v3 1/4] x86/membarrier: Get rid of a dubious optimization Andy Lutomirski
2020-12-09  4:10   ` Andy Lutomirski
2020-12-09  8:42   ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-12-04  5:07 ` [PATCH v3 2/4] membarrier: Add an actual barrier before rseq_preempt() Andy Lutomirski
2020-12-09  4:12   ` Andy Lutomirski
2020-12-09  8:42   ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-12-14 18:05     ` Andy Lutomirski [this message]
2020-12-04  5:07 ` [PATCH v3 3/4] membarrier: Explicitly sync remote cores when SYNC_CORE is requested Andy Lutomirski
2020-12-09  4:13   ` Andy Lutomirski
2020-12-09  8:42   ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski
2020-12-04  5:07 ` [PATCH v3 4/4] membarrier: Execute SYNC_CORE on the calling thread Andy Lutomirski
2020-12-04 19:35   ` Mathieu Desnoyers
2020-12-09  4:15   ` Andy Lutomirski
2020-12-09  8:42   ` [tip: x86/urgent] " tip-bot2 for Andy Lutomirski

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