From: Boqun Feng <boqun@kernel.org>
To: Shrikanth Hegde <sshegde@linux.ibm.com>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
"Ingo Molnar" <mingo@kernel.org>, "Will Deacon" <will@kernel.org>,
"Waiman Long" <longman@redhat.com>, "Gary Guo" <gary@garyguo.net>,
"Alice Ryhl" <aliceryhl@google.com>,
"Lyude Paul" <lyude@redhat.com>,
"Daniel Almeida" <daniel.almeida@collabora.com>,
"Onur Özkan" <work@onurozkan.dev>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Danilo Krummrich" <dakr@kernel.org>,
linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org
Subject: Re: [PATCH v4 10/17] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS
Date: Wed, 5 Aug 2026 00:27:01 -0700 [thread overview]
Message-ID: <anLlxZ0Qwh6PKzz_@tardis.local> (raw)
In-Reply-To: <9c59f7d4-03f3-4d7f-b77a-fdbab9a82ce7@linux.ibm.com>
On Wed, Aug 05, 2026 at 12:45:04PM +0530, Shrikanth Hegde wrote:
>
> Hi Boqun.
>
> > > nit: This limit is because to have the same behavior as other case when
> > > NMI_BITS=4 right?
> > > It is not easy to infer that from comment.
> > >
> >
> > It's sort of design by implementation IIUC, previously because of
> > NMI_BITS=4, we could only support nesting level being 15. And here we
> > just want to keep the same behavior here.
>
> That I understood.
>
> >
> > If your question is why 15 was a good number before this change, I guess
> > would be it's just a number that is neither too big or too small.
>
> Its more about below comment. Something like below is better?
>
> /* NMI nesting is represented in 4 bits. */
>
Sounds good, I will apply this, thank you!
Regards,
Boqun
> >
> > > > + /* Maximum NMI nesting is 15. */ \
> > > > + BUG_ON(__this_cpu_read(nmi_nesting) >= 15); \
> > > > + __this_cpu_inc(nmi_nesting); \
> > > > + preempt_count_set(preempt_count() | NMI_MASK); \
next prev parent reply other threads:[~2026-08-05 7:27 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-04 16:14 [PATCH v4 00/17] Refcounted interrupt disable and SpinLockIrq for Rust Boqun Feng
2026-08-04 16:14 ` [PATCH v4 01/17] preempt: Track NMI nesting to separate per-CPU counter Boqun Feng
2026-08-04 16:14 ` [PATCH v4 02/17] preempt: Introduce HARDIRQ_DISABLE_BITS Boqun Feng
2026-08-05 6:31 ` Peter Zijlstra
2026-08-05 6:59 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 03/17] preempt: Introduce __preempt_count_{sub,add}_return() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 04/17] openrisc: Include <linux/cpumask.h> in smp.h Boqun Feng
2026-08-04 16:14 ` [PATCH v4 05/17] irq & spin_lock: Add counted interrupt disabling/enabling Boqun Feng
2026-08-04 18:20 ` Boqun Feng
2026-08-04 18:26 ` [PATCH v4.1 " Boqun Feng
2026-08-04 20:51 ` [PATCH v4 " Shrikanth Hegde
2026-08-04 21:08 ` Boqun Feng
2026-08-05 6:36 ` Peter Zijlstra
2026-08-05 7:07 ` Boqun Feng
2026-08-05 7:09 ` Shrikanth Hegde
2026-08-05 7:19 ` Boqun Feng
2026-08-05 13:53 ` Boqun Feng
2026-08-05 14:10 ` Shrikanth Hegde
2026-08-05 14:20 ` Boqun Feng
2026-08-05 14:56 ` Shrikanth Hegde
2026-08-05 15:11 ` Boqun Feng
2026-08-05 16:53 ` Shrikanth Hegde
2026-08-05 17:38 ` Boqun Feng
2026-08-05 18:07 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 06/17] irq: Add KUnit test for refcounted interrupt enable/disable Boqun Feng
2026-08-04 16:14 ` [PATCH v4 07/17] locking: Switch to _irq_{disable,enable}() variants in cleanup guards Boqun Feng
2026-08-04 16:14 ` [PATCH v4 08/17] sched: Remove the unused preempt_offset parameter of __cant_sleep() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 09/17] sched: Avoid signed comparison of preempt_count() in __cant_migrate() Boqun Feng
2026-08-04 16:14 ` [PATCH v4 10/17] preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-04 20:11 ` Shrikanth Hegde
2026-08-05 6:54 ` Boqun Feng
2026-08-05 7:15 ` Shrikanth Hegde
2026-08-05 7:27 ` Boqun Feng [this message]
2026-08-06 0:58 ` Boqun Feng
2026-08-04 21:09 ` Shrikanth Hegde
2026-08-04 23:14 ` Boqun Feng
2026-08-04 16:14 ` [PATCH v4 11/17] arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS Boqun Feng
2026-08-04 16:14 ` [PATCH v4 12/17] s390/preempt: " Boqun Feng
2026-08-04 20:27 ` Shrikanth Hegde
2026-08-05 9:42 ` Peter Zijlstra
2026-08-05 12:37 ` Shrikanth Hegde
2026-08-04 16:14 ` [PATCH v4 13/17] rust: Introduce interrupt module Boqun Feng
2026-08-04 16:14 ` [PATCH v4 14/17] rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers Boqun Feng
2026-08-04 16:14 ` [PATCH v4 15/17] rust: sync: Use super::* in spinlock.rs Boqun Feng
2026-08-04 16:14 ` [PATCH v4 16/17] rust: sync: Add SpinLockIrq Boqun Feng
2026-08-04 16:14 ` [PATCH v4 17/17] rust: sync: Introduce SpinLockIrq::lock_with() and friends Boqun Feng
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