linux-kernel - Re: [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 23 Jan 2020 09:15:55 -0500
From:   Waiman Long <longman@...hat.com>
To:     Alex Kogan <alex.kogan@...cle.com>, linux@...linux.org.uk,
        peterz@...radead.org, mingo@...hat.com, will.deacon@....com,
        arnd@...db.de, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, bp@...en8.de, hpa@...or.com, x86@...nel.org,
        guohanjun@...wei.com, jglauber@...vell.com
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        dave.dice@...cle.com
Subject: Re: [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow
 path of qspinlock

On 1/14/20 10:59 PM, Alex Kogan wrote:
> +static int __init cna_init_nodes(void)
> +{
> +	unsigned int cpu;
> +
> +	/*
> +	 * this will break on 32bit architectures, so we restrict
> +	 * the use of CNA to 64bit only (see arch/x86/Kconfig)
> +	 */
> +	BUILD_BUG_ON(sizeof(struct cna_node) > sizeof(struct qnode));
> +	/* we store an ecoded tail word in the node's @locked field */
> +	BUILD_BUG_ON(sizeof(u32) > sizeof(unsigned int));
> +
> +	for_each_possible_cpu(cpu)
> +		cna_init_nodes_per_cpu(cpu);
> +
> +	return 0;
> +}
> +early_initcall(cna_init_nodes);
> +

I just realized that you shouldn't call cna_init_nodes as an
early_initcall. Instead,

> +/*
> + * Switch to the NUMA-friendly slow path for spinlocks when we have
> + * multiple NUMA nodes in native environment, unless the user has
> + * overridden this default behavior by setting the numa_spinlock flag.
> + */
> +void __init cna_configure_spin_lock_slowpath(void)
> +{
> +	if ((numa_spinlock_flag == 1) ||
> +	    (numa_spinlock_flag == 0 && nr_node_ids > 1 &&
> +		    pv_ops.lock.queued_spin_lock_slowpath ==
> +			native_queued_spin_lock_slowpath)) {
> +		pv_ops.lock.queued_spin_lock_slowpath =
> +		    __cna_queued_spin_lock_slowpath;
> +
> +		pr_info("Enabling CNA spinlock\n");
> +	}
> +}

call it when it is sure that CNA spinlock is going to be used. At this
point, the system is still in UP mode and the slowpath will not be called.

Cheers,
Longman