From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Ingo Molnar" <mingo@redhat.com>, "Will Deacon" <will@kernel.org>,
"Boqun Feng" <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org, john.p.donnelly@oracle.com,
"Hillf Danton" <hdanton@sina.com>,
"Mukesh Ojha" <quic_mojha@quicinc.com>,
"Ting11 Wang 王婷" <wangting11@xiaomi.com>
Subject: Re: [PATCH v3 2/5] locking/rwsem: Limit # of null owner retries for handoff writer
Date: Tue, 25 Oct 2022 15:55:09 -0400 [thread overview]
Message-ID: <d67740dc-d608-4b1a-0889-b9861153fdf3@redhat.com> (raw)
In-Reply-To: <Y1fNJZ9SALWlmoon@hirez.programming.kicks-ass.net>
On 10/25/22 07:48, Peter Zijlstra wrote:
> On Tue, Oct 25, 2022 at 01:22:22PM +0200, Peter Zijlstra wrote:
>
>> Funny, I find the former approach much saner. Disabling preemption
>> around the whole thing fixes the fundamental problem while spin-limiting
>> is a band-aid.
>>
>> Note how rwsem_write_trylock() already does preempt_disable(), having
>> the read-side do something similar only makes sense.
> Something like the completely untested below perhaps...
That is quite a number of changes spread over many different functions.
That is the kind of changes that may make it harder to backport to
stable releases.
This patch is just a stop-gap measure for stable releases which I
essentially revert in a later patch. I have no objection to disable
preemption in within the rwsem code exception to be backported to a
stable release. So I can add another patch on top of the series to
essentially do that.
Cheers,
Longman
next prev parent reply other threads:[~2022-10-25 19:55 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-17 21:13 [PATCH v3 0/5] lockinig/rwsem: Fix rwsem bugs & enable true lock handoff Waiman Long
2022-10-17 21:13 ` [PATCH v3 1/5] locking/rwsem: Prevent non-first waiter from spinning in down_write() slowpath Waiman Long
2022-10-24 13:17 ` Peter Zijlstra
2022-10-24 13:50 ` Waiman Long
2022-10-17 21:13 ` [PATCH v3 2/5] locking/rwsem: Limit # of null owner retries for handoff writer Waiman Long
2022-10-24 13:31 ` Peter Zijlstra
2022-10-24 15:55 ` Waiman Long
2022-10-25 11:22 ` Peter Zijlstra
2022-10-25 11:48 ` Peter Zijlstra
2022-10-25 19:55 ` Waiman Long [this message]
2022-10-25 20:14 ` Peter Zijlstra
2022-10-26 1:44 ` Waiman Long
[not found] ` <20221025145843.2953-1-hdanton@sina.com>
2022-10-25 19:00 ` Waiman Long
2022-10-17 21:13 ` [PATCH v3 3/5] locking/rwsem: Change waiter->hanodff_set to a handoff_state enum Waiman Long
2022-10-17 21:13 ` [PATCH v3 4/5] locking/rwsem: Enable direct rwsem lock handoff Waiman Long
2022-10-17 21:13 ` [PATCH v3 5/5] locking/rwsem: Update handoff lock events tracking Waiman Long
[not found] ` <20221018111424.1007-1-hdanton@sina.com>
2022-10-18 14:13 ` [PATCH v3 4/5] locking/rwsem: Enable direct rwsem lock handoff Mukesh Ojha
2022-10-18 17:37 ` Waiman Long
[not found] ` <20221018235138.1088-1-hdanton@sina.com>
2022-10-19 0:39 ` Waiman Long
[not found] ` <20221019022934.1166-1-hdanton@sina.com>
2022-10-19 2:49 ` Waiman Long
[not found] ` <20221019070559.1220-1-hdanton@sina.com>
2022-10-19 15:02 ` Waiman Long
2022-10-24 16:18 ` Waiman Long
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