From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Ingo Molnar" <mingo@kernel.org>,
"Waiman Long" <longman@redhat.com>,
"Arnd Bergmann" <arnd@arndb.de>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
"Guo Ren" <guoren@kernel.org>,
"Palmer Dabbelt" <palmerdabbelt@google.com>,
"Anup Patel" <anup@brainfault.org>,
linux-riscv <linux-riscv@lists.infradead.org>,
"Christoph Müllner" <christophm30@gmail.com>,
"Stafford Horne" <shorne@gmail.com>
Subject: Re: [PATCH] locking: Generic ticket lock
Date: Fri, 22 Oct 2021 14:31:00 +0200 [thread overview]
Message-ID: <20211022123100.GZ174703@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <YXKC9qh+evVmUuLI@FVFF77S0Q05N>
On Fri, Oct 22, 2021 at 10:23:02AM +0100, Mark Rutland wrote:
> Hi Peter,
>
> On Thu, Oct 21, 2021 at 03:05:15PM +0200, Peter Zijlstra wrote:
> > +static __always_inline void ticket_lock(arch_spinlock_t *lock)
> > +{
> > + u32 val = atomic_fetch_add_acquire(ONE_TICKET, lock);
>
> I wonder, should these atomics be arch_atomic_*(), in case an arch_ or raw_
> lock is used in noinstr code? The plain atomic_*() forms can have explicit
> inline instrumentation.
>
> I haven't seen any issues with qspinlock so far, and that also uses the
> (instrumented) atomics, so maybe that's not actually a problem, but I'm not
> sure what we intend here w.r.t. instrumentability.
So far it's not been a problem, and as you say, if we want to change
this, we need a larger audit/cleanup.
IIRC there's a potential problem in the arm idle code (noinstr'ing the
idle code is still on the TODO list somewhre, hampered by the need to
create more tooling).
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next prev parent reply other threads:[~2021-10-22 12:32 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 13:05 [PATCH] locking: Generic ticket lock Peter Zijlstra
2021-10-21 13:12 ` Peter Zijlstra
2021-10-21 13:50 ` Stafford Horne
2021-10-21 13:49 ` Arnd Bergmann
2021-10-21 15:14 ` Peter Zijlstra
2021-10-21 15:31 ` Arnd Bergmann
2021-10-21 16:28 ` Peter Zijlstra
2021-10-21 18:04 ` Waiman Long
2021-10-22 15:19 ` Boqun Feng
2021-10-22 2:04 ` Guo Ren
2021-10-22 9:23 ` Mark Rutland
2021-10-22 12:31 ` Peter Zijlstra [this message]
2021-12-14 15:40 ` Will Deacon
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