From: Byungchul Park <max.byungchul.park@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>,
Tejun Heo <tj@kernel.org>,
johannes.berg@intel.com, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
oleg@redhat.com, david@fromorbit.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
kernel-team@lge.com
Subject: Re: [PATCH] lockdep: Remove unnecessary acquisitions wrt workqueue flush
Date: Fri, 8 Sep 2017 06:19:57 +0900 [thread overview]
Message-ID: <CANrsvRNtVV25do-hdXEf6K5iHMrPoerdvHCpY=Wj8pvhr3ayhA@mail.gmail.com> (raw)
In-Reply-To: <20170907152107.v4wbvzi2zxlaelms@hirez.programming.kicks-ass.net>
On Fri, Sep 8, 2017 at 12:21 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Sep 07, 2017 at 08:37:08PM +0900, Byungchul Park wrote:
>> On Thu, Sep 7, 2017 at 6:41 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>> > On Thu, Sep 07, 2017 at 09:33:16AM +0900, Byungchul Park wrote:
>> >> Workqueue added manual acquisitions to catch deadlock cases. Now
>> >> crossrelease was introduced, some of those are redundant because
>> >> crossrelease-enabled wait_for_completeion() also does it. Removed it.
>> >
>> > This does not explain how it doesn't become the regular timing dependent
>> > stuff cross-release normally is.
>>
>> Yes, I will add more explanation for it at the next spin.
>>
>> But, let me explain it a bit here to help you get it, since it's very
>> simple. This has nothing to do with 'might' thing I introduced
>> previously. For 'might' thing, I will start it after getting your response.
>>
>> Here, I just removed acquire() because wait_for_completion()
>> already includes the acquire() by LOCKDEP_COMPLETIONS.
>> That's all.
>
> Ah I see, but it does so using some fairly nasty completion init stuff.
> The old code was far easier to read.
Agree.
But, old code has redundant acquisitions, moreover uses sub-class
to avoid false detection, even though they are the same class.
I will try to enhance readability of completion init, and fix the incorrect
use at the next spin.
--
Thanks,
Byungchul
prev parent reply other threads:[~2017-09-07 21:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 0:33 [PATCH] lockdep: Remove unnecessary acquisitions wrt workqueue flush Byungchul Park
2017-09-07 9:41 ` Peter Zijlstra
2017-09-07 11:37 ` Byungchul Park
2017-09-07 15:21 ` Peter Zijlstra
2017-09-07 21:19 ` Byungchul Park [this message]
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