linux-kernel - Re: [PATCH v2 5/5] freezer,sched: Rewrite core freezer logic

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Message-ID: <20220421175746.GB20402@redhat.com>
Date:   Thu, 21 Apr 2022 19:57:47 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, rjw@...ysocki.net,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        bigeasy@...utronix.de, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, tj@...nel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 5/5] freezer,sched: Rewrite core freezer logic

On 04/21, Eric W. Biederman wrote:
>
> I would like to say that we can do without the wait_task_inactive,
> but it looks like it is necessary to ensure that all of the userspace
> registers are saved where the tracer can get at them.

Yes, for example, fpu regs.

But there are more problems. For example, if debugger changes TIF_BLOCKSTEP
we need to ensure the child is already inactive and it will do another
switch_to() after that.

Oleg.