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From: Peter Oskolkov <posk@google.com>
To: Jann Horn <jannh@google.com>
Cc: Peter Oskolkov <posk@posk.io>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	Paul Turner <pjt@google.com>, Ben Segall <bsegall@google.com>,
	Andrei Vagin <avagin@google.com>,
	Thierry Delisle <tdelisle@uwaterloo.ca>
Subject: Re: [PATCH 3/4 v0.5] sched/umcg: RFC: implement UMCG syscalls
Date: Tue, 14 Sep 2021 09:51:28 -0700	[thread overview]
Message-ID: <CAPNVh5f6iaiYP8E2jKioirjJdwJDoJT-KHQLKjtgbr68H8-HxQ@mail.gmail.com> (raw)
In-Reply-To: <CAG48ez3Kd0sfKBi9CUSYDSd+ydkQ6H=zm2-iSB3jXHCyFvuWHw@mail.gmail.com>

On Wed, Sep 8, 2021 at 6:40 PM Jann Horn <jannh@google.com> wrote:

[...]

> I think umcg_idle_loop() should never be called from scheduler
> callbacks (meaning umcg_wq_worker_running()), only from UMCG syscalls.

I'm moving umcg_wq_worker_running() out of
core.c/sched_update_worker() and into
/kernel/entry/common.c/exit_to_user_mode_loop()
(and will rename the function appropriately).
It seems rescheduling/sleeping there is fine.

I'm not yet sure if this is all that is needed to deal with
UMCG_TF_PREEMPTED flag; but I don't expect to see
any locks held when the task truly returns to the userspace.

Maybe I'll need to set TIF_NOTIFY_RESUME in sched_update_worker()...

[...]

  reply	other threads:[~2021-09-14 16:51 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08 18:49 [PATCH 0/4 v0.5] sched/umcg: RFC UMCG patchset Peter Oskolkov
2021-09-08 18:49 ` [PATCH 1/4 v0.5] sched/umcg: add WF_CURRENT_CPU and externise ttwu Peter Oskolkov
2021-09-08 18:49 ` [PATCH 2/4 v0.5] sched/umcg: RFC: add userspace atomic helpers Peter Oskolkov
2021-09-08 23:38   ` Jann Horn
2021-09-09  1:16     ` Jann Horn
2021-09-09 19:06     ` Peter Oskolkov
2021-09-09 21:20       ` Jann Horn
2021-09-09 22:09         ` Peter Oskolkov
2021-09-09 23:13           ` Jann Horn
2021-09-14 16:52         ` Andy Lutomirski
2021-09-14 18:11           ` Peter Zijlstra
2021-09-14 18:40             ` Andy Lutomirski
2021-09-15 15:42               ` Peter Zijlstra
2021-09-15 16:50                 ` Andy Lutomirski
2021-09-15 19:10                   ` Peter Zijlstra
2021-09-14  8:07       ` Peter Zijlstra
2021-09-14 16:29         ` Peter Oskolkov
2021-09-14 18:04           ` Peter Zijlstra
2021-09-14 18:15             ` Peter Zijlstra
2021-09-14 18:29             ` Peter Oskolkov
2021-09-14 18:48               ` Peter Oskolkov
2021-09-08 18:49 ` [PATCH 3/4 v0.5] sched/umcg: RFC: implement UMCG syscalls Peter Oskolkov
2021-09-09  1:39   ` Jann Horn
2021-09-14 16:51     ` Peter Oskolkov [this message]
2021-09-08 18:49 ` [PATCH 4/4 v0.5] sched/umcg: add Documentation/userspace-api/umcg.rst Peter Oskolkov
2021-09-14 16:35   ` Tao Zhou
2021-09-14 16:57     ` Peter Oskolkov

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