linux-kernel - Re: [PATCH 1/2] hrtimer: Consider preemption when migrating hrtimer cpu

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: <51709FE1.20807@codeaurora.org>
Date:	Thu, 18 Apr 2013 18:37:37 -0700
From:	Michael Bohan <mbohan@...eaurora.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>, linux-arm-msm@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/2] hrtimer: Consider preemption when migrating hrtimer
 cpu_bases

On 4/18/2013 2:40 AM, Thomas Gleixner wrote:
> On Wed, 10 Apr 2013, Michael Bohan wrote:
>
>> When switching to a new cpu_base in switch_hrtimer_base(), we
>> briefly enable preemption by unlocking the cpu_base lock in two
>> places. During this interval it's possible for the running thread
>> to be swapped to a different CPU.
>>
>> Consider the following example:
>>
>> CPU #0                                 CPU #1
>> ----                                   ----
>> hrtimer_start()                        ...
>>   lock_hrtimer_base()
>>   switch_hrtimer_base()
>>    this_cpu = 0;
>>    target_cpu_base = 0;
>>    raw_spin_unlock(&cpu_base->lock)
>> <migrate to CPU 1>
>
> Errm. switch_hrtimer_base() is called with interrupts disabled and
> they stay disabled, so how exactly is the task going to be migrated?

My mistake - I missed that important fact. Please disregard this.

Thanks,
Mike

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
--
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/