linux-kernel - Re: [patch V4 part 1 05/36] x86/entry: Flip _TIF_SIGPENDING and _TIF_NOTIFY

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Message-ID: <20200514091940.GS2978@hirez.programming.kicks-ass.net>
Date:   Thu, 14 May 2020 11:19:40 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        rostedt <rostedt@...dmis.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, paulmck <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        "Joel Fernandes, Google" <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 1 05/36] x86/entry: Flip _TIF_SIGPENDING and
 _TIF_NOTIFY_RESUME handling

On Wed, May 13, 2020 at 10:51:53PM -0400, Mathieu Desnoyers wrote:

> Yes, I'm very well aware of this. But the patch commit message states:
> 
> "Make sure task_work runs before any kind of userspace -- very much
> including signals -- is invoked."
> 
> which seems to imply that "userspace" can be "invoked" before the task_work
> runs. Which makes no sense whatsoever. Hence my confused state.

I initially missed the run_task_work in the signal handling maze. Then
later figured this order still made more sense, but apparently there's
an actual problem.

I've no problem with the patch getting dropped.