From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Zhipeng Shi <zhipeng.shi0@gmail.com>
Cc: peterz@infradead.org, mingo@redhat.comb, will@kernel.org,
longman@redhat.com, boqun.feng@gmail.com, tglx@linutronix.de,
schspa@gmail.com, shengjian.xu@horizon.ai,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] locking/rtmutex: Provide proper spin_is_contended
Date: Tue, 7 Jun 2022 11:24:56 +0200 [thread overview]
Message-ID: <Yp8ZaHHBrHzg+o49@linutronix.de> (raw)
In-Reply-To: <20220607091514.897833-1-zhipeng.shi0@gmail.com>
On 2022-06-07 17:15:14 [+0800], Zhipeng Shi wrote:
> Commit d89c70356acf ("locking/core: Remove break_lock field when
> CONFIG_GENERIC_LOCKBREAK=y") removed GENERIC_LOCKBREAK, which caused
> spin_is_contended depend on the implementation of arch_spin_is_contended.
> But now in rt-spinlock, spin_is_contended returns 0 directly.
>
> This causes cond_resched_lock to fail to correctly detect lock contention
> in RT-linux. In some scenarios (such as __purge_vmap_area_lazy in vmalloc),
> this will cause a large latency.
>
> This patch provides the implementation of spin_is_contended for
> rt-spinlock.
Do you have a test-case or an example?
The thing if _this_ task has higher priority than other tasks waiting on
this lock then a simple unlock+lock won't do a thing. That is why I
ripped it all out while it was half way done.
> Signed-off-by: Zhipeng Shi <zhipeng.shi0@gmail.com>
Sebastian
next prev parent reply other threads:[~2022-06-07 9:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-07 9:15 [PATCH] locking/rtmutex: Provide proper spin_is_contended Zhipeng Shi
2022-06-07 9:24 ` Sebastian Andrzej Siewior [this message]
2022-06-08 14:24 ` Zhipeng Shi
-- strict thread matches above, loose matches on Subject: below --
2022-06-07 9:24 Zhipeng Shi
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