From: Peter Zijlstra <peterz@infradead.org>
To: Lyude Paul <lyude@redhat.com>
Cc: rust-for-linux@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Boqun Feng <boqun.feng@gmail.com>, Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
"open list:SCHEDULER" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v9 1/9] preempt: Introduce HARDIRQ_DISABLE_BITS
Date: Fri, 28 Feb 2025 08:57:55 +0100 [thread overview]
Message-ID: <20250228075755.GC5880@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250227221924.265259-2-lyude@redhat.com>
On Thu, Feb 27, 2025 at 05:10:12PM -0500, Lyude Paul wrote:
> @@ -26,29 +27,34 @@
> *
> * PREEMPT_MASK: 0x000000ff
> * SOFTIRQ_MASK: 0x0000ff00
> - * HARDIRQ_MASK: 0x000f0000
> - * NMI_MASK: 0x00f00000
> + * HARDIRQ_DISABLE_MASK: 0x00ff0000
> + * HARDIRQ_MASK: 0x07000000
> + * NMI_MASK: 0x38000000
> * PREEMPT_NEED_RESCHED: 0x80000000
> */
> #define PREEMPT_BITS 8
> #define SOFTIRQ_BITS 8
> -#define HARDIRQ_BITS 4
> -#define NMI_BITS 4
> +#define HARDIRQ_DISABLE_BITS 8
> +#define HARDIRQ_BITS 3
> +#define NMI_BITS 3
I'm a bit scared here. This reduces the number of NMI levels from 16 to
8, and we have 5 IST gates that can nest in wonderful ways. This might
just be achievable.
Also, you should probably double check the HARDIRQ bits against all
architectures that have interrupt priority support -- Linux doesn't
really do that, local_irq_disable() is typically disable-all, but things
like PowerPC play funny games -- ideally those games are all played
before entering the common code that has the accounting on.
And I don't think we have overflow detection on the NMI/IRQ bits.
The comment with __nmi_enter() is now wrong.
Anyway, like I said before, I like the general idea, but I hate we're
growing a 3rd form.
next prev parent reply other threads:[~2025-02-28 7:58 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-27 22:10 [PATCH v9 0/9] Refcounted interrupts, SpinLockIrq for rust Lyude Paul
2025-02-27 22:10 ` [PATCH v9 1/9] preempt: Introduce HARDIRQ_DISABLE_BITS Lyude Paul
2025-02-27 23:09 ` Steven Rostedt
2025-02-28 1:33 ` Boqun Feng
2025-03-03 21:55 ` Lyude Paul
2025-02-28 7:57 ` Peter Zijlstra [this message]
2025-02-27 22:10 ` [PATCH v9 2/9] preempt: Introduce __preempt_count_{sub, add}_return() Lyude Paul
2025-02-28 1:49 ` Boqun Feng
2025-02-28 9:15 ` Heiko Carstens
2025-02-28 9:24 ` Peter Zijlstra
2025-04-30 21:38 ` Lyude Paul
2025-05-05 9:56 ` Heiko Carstens
2025-03-01 18:49 ` kernel test robot
2025-03-01 19:00 ` kernel test robot
2025-02-27 22:10 ` [PATCH v9 3/9] irq & spin_lock: Add counted interrupt disabling/enabling Lyude Paul
2025-03-01 20:19 ` kernel test robot
2025-02-27 22:10 ` [PATCH v9 4/9] rust: Introduce interrupt module Lyude Paul
2025-03-02 16:56 ` Dirk Behme
2025-02-27 22:10 ` [PATCH v9 5/9] rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers Lyude Paul
2025-02-27 22:10 ` [PATCH v9 6/9] rust: sync: Add SpinLockIrq Lyude Paul
2025-03-02 11:51 ` Guangbo Cui
2025-03-03 22:15 ` Lyude Paul
2025-03-02 17:07 ` Dirk Behme
2025-04-04 21:56 ` Lyude Paul
2025-02-27 22:10 ` [PATCH v9 7/9] rust: sync: Introduce lock::Backend::Context Lyude Paul
2025-03-03 14:22 ` Dirk Behme
2025-02-27 22:10 ` [PATCH v9 8/9] rust: sync: lock: Add `Backend::BackendInContext` Lyude Paul
2025-03-03 14:23 ` Dirk Behme
2025-02-27 22:10 ` [PATCH v9 9/9] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Lyude Paul
2025-04-05 8:25 ` Guangbo Cui
2025-04-05 8:55 ` Guangbo Cui
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