linux-kernel - Re: [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers

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]

Message-ID: <20150824012849.GB20044@lerouge>
Date:	Mon, 24 Aug 2015 03:28:51 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Vatika Harlalka <vatikaharlalka@...il.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH RESEND] sched/nohz: Affine unpinned timers to housekeepers

On Sun, Aug 23, 2015 at 09:01:01AM -0700, Paul E. McKenney wrote:
> The boot CPU is excluded from tick_nohz_full_mask in tick_nohz_init(),
> which is called from tick_init() which is called from start_kernel()
> shortly after rcu_init():
> 
> 	cpu = smp_processor_id();
> 
> 	if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
> 		pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
> 		cpumask_clear_cpu(cpu, tick_nohz_full_mask);
> 	}
> 
> This happens after the call to tick_nohz_init_all() that does the
> cpumask_setall() that you called out above.
> 
> Or is a recent patch that I missed changing this?

Exactly, this happens right after tick_nohz_full_mask is filled and
makes sure that at least the boot CPU runs as a housekeeper. We
also make sure that it can't become offline later.

Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/