From: Tiwei Bie <tiwei.bie@linux.dev>
To: johannes@sipsolutions.net
Cc: richard@nod.at, anton.ivanov@cambridgegreys.com,
benjamin@sipsolutions.net, arnd@arndb.de,
linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
tiwei.btw@antgroup.com, tiwei.bie@linux.dev
Subject: Re: [PATCH v2 05/10] um: Determine sleep based on need_resched()
Date: Thu, 11 Sep 2025 12:39:18 +0800 [thread overview]
Message-ID: <20250911043918.2950727-1-tiwei.bie@linux.dev> (raw)
In-Reply-To: <55cace5b8e1078bd04b4a1acb5df9faa6a83b6e8.camel@sipsolutions.net>
On Wed, 10 Sep 2025 14:10:37 +0200, Johannes Berg wrote:
> On Sun, 2025-08-10 at 13:51 +0800, Tiwei Bie wrote:
> > From: Tiwei Bie <tiwei.btw@antgroup.com>
> >
> > With SMP and NO_HZ enabled, the CPU may still need to sleep even
> > if the timer is disarmed. Switch to deciding whether to sleep based
> > on pending resched. This is a preparation for adding SMP support.
>
> What's the rationale for need_resched()? Is that somehow defined for
> this? Is it what other architectures use? I guess I'm just not entirely
> sure what it means.
Here is a relevant document:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/scheduler/sched-arch.rst?h=v6.17-rc5#n37
There is a similar check on x86:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/process.c?h=v6.17-rc5#n916
Regards,
Tiwei
next prev parent reply other threads:[~2025-09-11 4:39 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-10 5:51 [PATCH v2 00/10] um: Add SMP support Tiwei Bie
2025-08-10 5:51 ` [PATCH v2 01/10] um: Stop tracking virtual CPUs via mm_cpumask() Tiwei Bie
2025-08-10 5:51 ` [PATCH v2 02/10] um: Remove unused cpu_data and current_cpu_data macros Tiwei Bie
2025-08-10 5:51 ` [PATCH v2 03/10] um: vdso: Implement __vdso_getcpu() via syscall Tiwei Bie
2025-09-10 11:59 ` Johannes Berg
2025-09-11 4:29 ` Tiwei Bie
2025-09-21 20:00 ` Thomas Weißschuh
2025-09-22 4:50 ` Tiwei Bie
2025-09-22 12:05 ` Thomas Weißschuh
2025-09-22 12:12 ` Johannes Berg
2025-09-22 14:01 ` Thomas Weißschuh
2025-09-22 15:14 ` Johannes Berg
2025-09-22 16:04 ` Thomas Weißschuh
2025-09-22 17:07 ` Johannes Berg
2025-09-25 17:08 ` Thomas Weißschuh
2025-10-21 13:20 ` Johannes Berg
2025-08-10 5:51 ` [PATCH v2 04/10] um: Turn signals_* into thread-local variables Tiwei Bie
2025-09-10 12:15 ` Johannes Berg
2025-09-11 4:34 ` Tiwei Bie
2025-09-11 7:37 ` Benjamin Berg
2025-09-11 8:06 ` Benjamin Berg
2025-09-12 0:30 ` Tiwei Bie
2025-09-12 7:58 ` Benjamin Berg
2025-09-12 13:27 ` Tiwei Bie
2025-09-11 9:44 ` Johannes Berg
2025-09-11 10:35 ` Benjamin Berg
2025-08-10 5:51 ` [PATCH v2 05/10] um: Determine sleep based on need_resched() Tiwei Bie
2025-09-10 12:10 ` Johannes Berg
2025-09-11 4:39 ` Tiwei Bie [this message]
2025-09-11 6:59 ` Johannes Berg
2025-09-12 0:59 ` Tiwei Bie
2025-09-11 9:27 ` Johannes Berg
2025-09-12 0:54 ` Tiwei Bie
2025-08-10 5:51 ` [PATCH v2 06/10] um: Define timers on a per-CPU basis Tiwei Bie
2025-08-10 9:49 ` kernel test robot
2025-08-10 5:51 ` [PATCH v2 07/10] um: Remove unused ipi_pipe field from cpuinfo_um Tiwei Bie
2025-08-10 5:51 ` [PATCH v2 08/10] um: Add initial SMP support Tiwei Bie
2025-09-11 9:32 ` Johannes Berg
2025-09-12 0:45 ` Tiwei Bie
2025-09-12 7:58 ` Johannes Berg
2025-08-10 5:51 ` [PATCH v2 09/10] asm-generic: percpu: Add assembly guard Tiwei Bie
2025-09-10 12:12 ` Johannes Berg
2025-08-10 5:51 ` [PATCH v2 10/10] um: Enable SMP support on x86 Tiwei Bie
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