From: Ard Biesheuvel <ardb@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, James Morse <james.morse@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2] arm64: implement support for static call trampolines
Date: Thu, 29 Oct 2020 12:49:52 +0100 [thread overview]
Message-ID: <CAMj1kXFCjuDtJHj7DcQcfTmQVqN14pzYb=YGe70giwLgWJNXbQ@mail.gmail.com> (raw)
In-Reply-To: <20201029114605.GM2628@hirez.programming.kicks-ass.net>
On Thu, 29 Oct 2020 at 12:46, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Thu, Oct 29, 2020 at 11:58:52AM +0100, Ard Biesheuvel wrote:
> > On Thu, 29 Oct 2020 at 11:40, Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > Would it make things easier if your trampoline consisted of two complete
> > > slots, between which you can flip?
> > >
> > > Something like:
> > >
> > > 0x00 B 0x24 / NOP
> > > 0x04 < slot 1 >
> > > ....
> > > 0x20
> > > 0x24 < slot 2 >
> > > ....
> > > 0x40
> > >
> > > Then each (20 byte) slot can contain any of the variants above and you
> > > can write the unused slot without stop-machine. Then, when the unused
> > > slot is populated, flip the initial instruction (like a static-branch),
> > > issue synchronize_rcu_tasks() and flip to using the other slot for next
> > > time.
> > >
> >
> > Once we've populated a slot and activated it, we have to assume that
> > it is live and we can no longer modify it freely.
>
> Urhm how so? Once you pass through synchronize_rcu_tasks() nobody should
> still be using the old one.
But doesn't that require some RCU foo in the static call wrapper itself?
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next prev parent reply other threads:[~2020-10-29 11:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 18:41 [PATCH v2] arm64: implement support for static call trampolines Ard Biesheuvel
2020-10-29 10:28 ` Peter Zijlstra
2020-10-29 10:40 ` Peter Zijlstra
2020-10-29 10:58 ` Ard Biesheuvel
2020-10-29 11:46 ` Peter Zijlstra
2020-10-29 11:49 ` Ard Biesheuvel [this message]
2020-10-29 11:54 ` Peter Zijlstra
2020-10-29 12:14 ` Ard Biesheuvel
2020-10-29 11:27 ` Quentin Perret
2020-10-29 11:32 ` Ard Biesheuvel
2020-10-29 11:44 ` Peter Zijlstra
2020-10-29 14:10 ` Steven Rostedt
2020-10-29 11:54 ` Quentin Perret
2020-10-29 13:22 ` Ard Biesheuvel
2020-11-16 10:18 ` Quentin Perret
2020-11-16 10:31 ` Ard Biesheuvel
2020-11-16 12:05 ` Quentin Perret
2020-10-29 11:50 ` Mark Rutland
2020-10-29 11:58 ` Peter Zijlstra
2020-10-29 13:30 ` Mark Rutland
2020-10-29 11:59 ` Ard Biesheuvel
2020-10-29 13:21 ` Mark Rutland
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