From: Greg KH <gregkh@linuxfoundation.org>
To: Zheng Yejian <zhengyejian1@huawei.com>
Cc: lee.jones@linaro.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
cj.chengjian@huawei.com, judy.chenhui@huawei.com,
zhangjinhao2@huawei.com, nixiaoming@huawei.com
Subject: Re: [PATCH 4.4 1/3] futex: Change locking rules
Date: Tue, 9 Mar 2021 11:40:16 +0100 [thread overview]
Message-ID: <YEdQkLfQR9HRobUA@kroah.com> (raw)
In-Reply-To: <20210309030605.3295183-2-zhengyejian1@huawei.com>
On Tue, Mar 09, 2021 at 11:06:03AM +0800, Zheng Yejian wrote:
> From: Peter Zijlstra <peterz@infradead.org>
>
> Currently futex-pi relies on hb->lock to serialize everything. But hb->lock
> creates another set of problems, especially priority inversions on RT where
> hb->lock becomes a rt_mutex itself.
>
> The rt_mutex::wait_lock is the most obvious protection for keeping the
> futex user space value and the kernel internal pi_state in sync.
>
> Rework and document the locking so rt_mutex::wait_lock is held accross all
> operations which modify the user space value and the pi state.
>
> This allows to invoke rt_mutex_unlock() (including deboost) without holding
> hb->lock as a next step.
>
> Nothing yet relies on the new locking rules.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: juri.lelli@arm.com
> Cc: bigeasy@linutronix.de
> Cc: xlpang@redhat.com
> Cc: rostedt@goodmis.org
> Cc: mathieu.desnoyers@efficios.com
> Cc: jdesfossez@efficios.com
> Cc: dvhart@infradead.org
> Cc: bristot@redhat.com
> Link: http://lkml.kernel.org/r/20170322104151.751993333@infradead.org
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> [Lee: Back-ported in support of a previous futex back-port attempt]
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
> ---
> kernel/futex.c | 138 +++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 112 insertions(+), 26 deletions(-)
What is the git commit id of this patch in Linus's tree?
thanks,
greg k-h
next prev parent reply other threads:[~2021-03-09 10:40 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 3:06 [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Zheng Yejian
2021-03-09 3:06 ` [PATCH 4.4 1/3] futex: Change locking rules Zheng Yejian
2021-03-09 10:40 ` Greg KH [this message]
2021-03-09 3:06 ` [PATCH 4.4 2/3] futex: Cure exit race Zheng Yejian
2021-03-09 3:06 ` [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner() Zheng Yejian
2021-03-09 10:40 ` Greg KH
2021-03-09 18:14 ` Lee Jones
2021-03-10 12:00 ` Greg KH
2021-03-10 13:28 ` Lee Jones
2021-03-10 14:10 ` Greg KH
2021-03-11 1:39 ` Zhengyejian (Zetta)
2021-03-09 10:41 ` [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Greg KH
2021-03-11 3:48 ` Zhengyejian (Zetta)
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