linux-kernel - Re: [PATCH 08/14] hrtimer: Allow hrtimer::function() to free the timer

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: <20150607225638.GA9329@redhat.com>
Date:	Mon, 8 Jun 2015 00:56:38 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	umgwanakikbuti@...il.com, mingo@...e.hu, ktkhai@...allels.com,
	rostedt@...dmis.org, tglx@...utronix.de, juri.lelli@...il.com,
	pang.xunlei@...aro.org, wanpeng.li@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/14] hrtimer: Allow hrtimer::function() to free the
	timer

On 06/08, Oleg Nesterov wrote:
>
> And I simply can not understand the complication in hrtimer_active(),
> please help!

Sorry for another off-topic email, but I don't even understand the
usage of hrtimer_active().

Say, do_nanosleep()

		hrtimer_start_expires(&t->timer, mode);
		if (!hrtimer_active(&t->timer))
			t->task = NULL;

why? Assuming that hrtimer_active() is correct, it can only return
false if t->task was already cleared by hrtimer_wakeup().


OTOH. perf_cpu_hrtimer_restart() does

	if (hrtimer_active(hr))
		return;

	if (!hrtimer_callback_running(hr))
		__hrtimer_start_range_ns(...);

why it can't simply do

	if (!hrtimer_active(hr)) // implies !hrtimer_callback_running()
		__hrtimer_start_range_ns(...);


Confused.

Oleg.

--
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/