linux-kernel - Re: [PATCH v2 4/5] riscv: add lazy preempt support

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Message-ID: <YxW3cZEhEideZon2@linutronix.de>
Date:   Mon, 5 Sep 2022 10:46:41 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Guo Ren <guoren@...nel.org>
Cc:     Jisheng Zhang <jszhang@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 4/5] riscv: add lazy preempt support

On 2022-09-05 16:33:54 [+0800], Guo Ren wrote:
> > There is "generic" code in the PREEMPT_RT patch doing that. The counter
> > is incremented/ decremented via preempt_lazy_enable()/disable() and one
> > of the user is migrate_disable()/enable().
> > Basically if a task is task_is_realtime() then NEED_RESCHED is set for
> > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY
> > is set for the wakeup. This can be delayed if the task is in a "preempt
> > disable lazy" section (similar to a preempt_disable() section) but a
> > task_is_realtime() can still be scheduled if needed.
> Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY
> [1], so above assembly code would be replaced by generic one, right?

correct.

Sebastian