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).
next prev parent reply other threads:[~2021-10-22 12:33 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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