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From: Andy Lutomirski <luto@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, Anton Blanchard <anton@ozlabs.org>,
	stable <stable@vger.kernel.org>
Subject: Re: [PATCH v3 1/4] x86/membarrier: Get rid of a dubious optimization
Date: Tue, 8 Dec 2020 20:10:17 -0800	[thread overview]
Message-ID: <CALCETrULOhzyTjd+K5ByeRZ2Sn2-EjpaMJd2DosZ-V1X5DUojA@mail.gmail.com> (raw)
In-Reply-To: <5afc7632be1422f91eaf7611aaaa1b5b8580a086.1607058304.git.luto@kernel.org>

On Thu, Dec 3, 2020 at 9:07 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> sync_core_before_usermode() had an incorrect optimization.  If we're
> in an IRQ, we can get to usermode without IRET -- we just have to
> schedule to a different task in the same mm and do SYSRET.
> Fortunately, there were no callers of sync_core_before_usermode()
> that could have had in_irq() or in_nmi() equal to true, because it's
> only ever called from the scheduler.
>
> While we're at it, clarify a related comment.
>

Fixes: ac1ab12a3e6e ("lockin/x86: Implement sync_core_before_usermode()")

> Cc: stable@vger.kernel.org
> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

  reply	other threads:[~2020-12-09  4:11 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 [this message]
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
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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