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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, "Sasha Levin" <sasha.levin@oracle.com>,
	"Brian Gerst" <brgerst@gmail.com>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Denys Vlasenko" <dvlasenk@redhat.com>,
	linux-kernel@vger.kernel.org, "Oleg Nesterov" <oleg@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: [PATCH] x86/traps: Weaken context tracking entry assertions
Date: Fri, 21 Aug 2015 08:23:28 +0200	[thread overview]
Message-ID: <20150821062328.GA32366@gmail.com> (raw)
In-Reply-To: <c81faf3916346c0e04346c441392974f49cd7184.1440133286.git.luto@kernel.org>


* Andy Lutomirski <luto@kernel.org> wrote:

> We were asserting that we were all the way in CONTEXT_KERNEL when exception 
> handlers were called.  While having this be true is, I think, a nice goal (or 
> maybe a variant in which we assert that we're in CONTEXT_KERNEL or some new IRQ 
> context), we're not quite there.
> 
> In particular, if an IRQ interrupts the SYSCALL prologue and the IRQ handler in 
> turn causes an exception, the exception entry will be called in RCU IRQ mode but 
> with CONTEXT_USER.

Hm, so what harm would there be in making IRQ handlers enter CONTEXT_KERNEL?
Would nohz-full break?

I'd rather have a bit more tracking overhead here than lose such useful sanity 
checks.

Thanks,

	Ingo

  reply	other threads:[~2015-08-21  6:23 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-08-21  5:03 Andy Lutomirski
2015-08-21  6:23 ` Ingo Molnar [this message]
2015-08-21 13:38   ` Frederic Weisbecker
2015-08-21 14:39   ` Andy Lutomirski
2015-08-21 13:24 ` Frederic Weisbecker
2015-08-22 13:57 ` [tip:core/core] " tip-bot for Andy Lutomirski

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