From: Mark Rutland <mark.rutland@arm.com>
To: Valentin Schneider <vschneid@redhat.com>
Cc: Jinjie Ruan <ruanjinjie@huawei.com>,
catalin.marinas@arm.com, will@kernel.org, oleg@redhat.com,
sstabellini@kernel.org, tglx@linutronix.de, peterz@infradead.org,
luto@kernel.org, mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
kees@kernel.org, aliceryhl@google.com, ojeda@kernel.org,
samitolvanen@google.com, masahiroy@kernel.org, rppt@kernel.org,
xur@google.com, paulmck@kernel.org, arnd@arndb.de,
puranjay@kernel.org, broonie@kernel.org, mbenes@suse.cz,
sudeep.holla@arm.com, guohanjun@huawei.com, prarit@redhat.com,
liuwei09@cestc.cn, Jonathan.Cameron@huawei.com,
dwmw@amazon.co.uk, kristina.martsenko@arm.com,
liaochang1@huawei.com, ptosi@google.com,
thiago.bauermann@linaro.org, kevin.brodsky@arm.com,
Dave.Martin@arm.com, joey.gouly@arm.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH -next v6 8/8] arm64: entry: Switch to generic IRQ entry
Date: Thu, 27 Feb 2025 18:35:26 +0000 [thread overview]
Message-ID: <Z8CwbmCXguCEfJvx@J2N7QTR9R3> (raw)
In-Reply-To: <xhsmh4j0fl0p3.mognet@vschneid-thinkpadt14sgen2i.remote.csb>
On Thu, Feb 27, 2025 at 07:08:56PM +0100, Valentin Schneider wrote:
> On 13/02/25 21:00, Jinjie Ruan wrote:
> > Currently, x86, Riscv, Loongarch use the generic entry. Convert arm64
> > to use the generic entry infrastructure from kernel/entry/*.
> > The generic entry makes maintainers' work easier and codes
> > more elegant.
> >
> > Switch arm64 to generic IRQ entry first, which removed duplicate 100+
> > LOC and make Lazy preemption on arm64 available by adding a
> > _TIF_NEED_RESCHED_LAZY bit and enabling ARCH_HAS_PREEMPT_LAZY.
>
> Just a drive-by comment as I'm interested in lazy preemption for arm64;
> this series doesn't actually enable lazy preemption, is that for a
> follow-up with the rest of the generic entry stuff?
>
> From a quick glance, it looks like everything is in place for enabling it.
Sorry, there's been some fractured discussion on this on the
linux-rt-users list:
https://lore.kernel.org/linux-rt-users/20241216190451.1c61977c@mordecai.tesarici.cz/
The TL;DR is that lazy preemption doesn't actually depend on generic
entry, and we should be able to enable it on arm64 independently of this
series. I'd posted a quick hack which Mike Galbraith cleaned up:
https://lore.kernel.org/linux-rt-users/a198a7dd9076f97b89d8882bb249b3bf303564ef.camel@gmx.de/
... but that was never posted as a new thread to LAKML.
Would you be happy to take charge and take that patch, test it, and post
it here (or spin your own working version)? I was happy with the way it
looks but hadn't had the time for testing and so on.
I expect that we'll merge the generic entry code too, but having them
separate is a bit easier for bisection and backporting where people want
lazy preemption in downstream trees.
Mark.
next prev parent reply other threads:[~2025-02-27 19:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-13 12:59 [PATCH -next v6 0/8] arm64: entry: Convert to generic irq entry Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 1/8] entry: Split generic entry into generic exception and syscall entry Jinjie Ruan
2025-03-20 14:26 ` Linus Walleij
2025-04-28 14:46 ` Linus Walleij
2025-04-29 15:03 ` Will Deacon
2025-02-13 13:00 ` [PATCH -next v6 2/8] arm64: ptrace: Replace interrupts_enabled() with regs_irqs_disabled() Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 3/8] arm64: entry: Refactor the entry and exit for exceptions from EL1 Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 4/8] arm64: entry: Rework arm64_preempt_schedule_irq() Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 5/8] arm64: entry: Use preempt_count() and need_resched() helper Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 6/8] arm64: entry: Refactor preempt_schedule_irq() check code Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 7/8] arm64: entry: Move arm64_preempt_schedule_irq() into __exit_to_kernel_mode() Jinjie Ruan
2025-02-13 13:00 ` [PATCH -next v6 8/8] arm64: entry: Switch to generic IRQ entry Jinjie Ruan
2025-02-27 18:08 ` Valentin Schneider
2025-02-27 18:35 ` Mark Rutland [this message]
2025-02-27 21:29 ` Valentin Schneider
2025-04-14 9:13 ` [PATCH -next v6 0/8] arm64: entry: Convert to generic irq entry Jinjie Ruan
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