linux-ext4 - Re: [PATCH 0/7 v2] jbd2: Bit spinlock conversions

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Message-ID: <20191011123105.s6qjwrlgugszk73j@linutronix.de>
Date:   Fri, 11 Oct 2019 14:31:07 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Julia Cartwright <julia@...com>
Subject: Re: [PATCH 0/7 v2] jbd2: Bit spinlock conversions

On 2019-08-09 14:42:26 [+0200], Jan Kara wrote:
> Hello,
Hi,

> This series is derived from Thomas' series to get rid of bit spinlocks in
> buffer head code. These patches convert BH_State bit spinlock to an ordinary
> spinlock inside struct journal_head and somewhat reduce the critical section
> under BH_JournalHead bit spinlock so that it is fine for RT. 
> 
> Motivation from original Thomas' series:
> 
> Bit spinlocks are problematic if PREEMPT_RT is enabled. They disable
> preemption, which is undesired for latency reasons and breaks when regular
> spinlocks are taken within the bit_spinlock locked region because regular
> spinlocks are converted to 'sleeping spinlocks' on RT.
> 
> Bit spinlocks are also not covered by lock debugging, e.g. lockdep. With
> the spinlock substitution in place, they can be exposed via a new config
> switch: CONFIG_DEBUG_BIT_SPINLOCKS.
> 
> Ted, can you pick up these patches? Thanks!

Has this series been postponed?

> Changes since v1:
> * Fixed up compilation breakage on UP due to missing linux/spinlock.h include
> 
> 								Honza

Sebastian