linux-kernel - Re: [PATCH V3 4/5] cpufreq: governor: Quit work-handlers early if governor is stopped

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] [day] [month] [year] [list]

Message-ID: <20151028144655.GC3716@ubuntu>
Date:	Wed, 28 Oct 2015 20:16:55 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 4/5] cpufreq: governor: Quit work-handlers early if
 governor is stopped

On 28-10-15, 16:12, Rafael J. Wysocki wrote:
> So this is a changelog matching your patch:
> 
> "gov_queue_work() acquires cpufreq_governor_lock to allow cpufreq_governor_stop()
> to drain delayed work items possibly scheduled on CPUs that share the policy with
> a CPU being taken offline.
> 
> However, the same goal may be achieved in a more straightforward way if the
> policy pointer in the struct cpu_dbs_info matching the policy CPU is reset
> upfront by cpufreq_governor_stop() under the timer_mutex belonging to it and
> checked against NULL, under the same lock, at the beginning of dbs_timer().
> 
> In that case every instance of dbs_timer() run for a struct cpu_dbs_info
> sharing the policy pointer in question after cpufreq_governor_stop() has started
> will notice that that pointer is NULL and bail out immediately without queuing up
> any new work items.  In turn, gov_cancel_work() called by cpufreq_governor_stop()
> before destroying timer_mutex will wait for all of the delayed work items
> currently running on the CPUs sharing the policy to drop the mutex, so it may
> be destroyed safely.
> 
> Make cpufreq_governor_stop() and dbs_timer() work as described and modify
> gov_queue_work() so it does not acquire cpufreq_governor_lock any more."

Looks far better, thanks :)

-- 
viresh
--
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/