linux-kernel - Re: [RFC PATCH v1] pin_on_cpu: Introduce thread CPU pinning system call

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Message-ID: <alpine.DEB.2.21.2001212141590.1231@www.lameter.com>
Date:   Tue, 21 Jan 2020 21:44:28 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
cc:     Jann Horn <jannh@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Watson <davejwatson@...com>,
        Will Deacon <will.deacon@....com>, shuah <shuah@...nel.org>,
        Andi Kleen <andi@...stfloor.org>,
        linux-kselftest <linux-kselftest@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Russell King <linux@....linux.org.uk>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Paul <paulmck@...ux.vnet.ibm.com>, Paul Turner <pjt@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        rostedt <rostedt@...dmis.org>, Ben Maurer <bmaurer@...com>,
        linux-api <linux-api@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [RFC PATCH v1] pin_on_cpu: Introduce thread CPU pinning system
 call


These scenarios are all pretty complex and will be difficult to understand
for the user of these APIs.

I think the easiest solution (and most comprehensible) is for the user
space process that does per cpu operations to get some sort of signal. If
its not able to handle that then terminate it. The code makes a basic
assumption after all that the process is running on a specific cpu. If
this is no longer the case then its better to abort if the process cannot
handle moving to a different processor.