linux-kernel - Re: [RFC PATCH v11 for 4.15 01/24] Restartable sequences system call

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Message-ID: <20171116161815.dg4hi2z35rkh4u4s@hirez.programming.kicks-ass.net>
Date:   Thu, 16 Nov 2017 17:18:15 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Watson <davejwatson@...com>, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, Andrew Hunter <ahh@...gle.com>,
        Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
        Ben Maurer <bmaurer@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        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>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC PATCH v11 for 4.15 01/24] Restartable sequences system call

On Tue, Nov 14, 2017 at 03:03:51PM -0500, Mathieu Desnoyers wrote:
> @@ -977,6 +978,13 @@ struct task_struct {
>  	unsigned long			numa_pages_migrated;
>  #endif /* CONFIG_NUMA_BALANCING */
>  
> +#ifdef CONFIG_RSEQ
> +	struct rseq __user *rseq;
> +	u32 rseq_len;
> +	u32 rseq_sig;
> +	bool rseq_preempt, rseq_signal, rseq_migrate;

No bool please. Use something that has a defined size in ILP32/LP64.
_Bool makes it absolutely impossible to speculate on structure layout
across architectures.

> +#endif
> +
>  	struct tlbflush_unmap_batch	tlb_ubc;
>  
>  	struct rcu_head			rcu;