linux-kernel - Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread

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Message-ID: <alpine.DEB.2.11.1602241206020.3670@nanos>
Date:	Wed, 24 Feb 2016 12:11:15 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <linux@....linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Andrew Hunter <ahh@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Watson <davejwatson@...com>, Chris Lameter <cl@...ux.com>,
	Ben Maurer <bmaurer@...com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of
 running thread

On Tue, 23 Feb 2016, Mathieu Desnoyers wrote:
> +/*
> + * If parent process has a thread-local ABI, the child inherits. Only applies
> + * when forking a process, not a thread.
> + */
> +void getcpu_cache_fork(struct task_struct *t)
> +{
> +	t->cpu_cache = current->cpu_cache;
> +}
> +
> +void getcpu_cache_execve(struct task_struct *t)
> +{
> +	t->cpu_cache = NULL;
> +}
> +
> +void getcpu_cache_exit(struct task_struct *t)
> +{
> +	t->cpu_cache = NULL;
> +}

That's hardly worth a function call. Please inline.

> +/*
> + * sys_getcpu_cache - setup getcpu cache for caller thread
> + */
> +SYSCALL_DEFINE3(getcpu_cache, int, cmd, int32_t __user * __user *, cpu_cachep,
> +		int, flags)
> +{
> +	if (unlikely(flags))
> +		return -EINVAL;

New line for readability sake.

> +	switch (cmd) {
> +	case GETCPU_CACHE_GET:

Other than that: Reviewed-by: Thomas Gleixner <tglx@...utronix.de>