From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
Nilay Shroff <nilay@linux.ibm.com>,
linux-block@vger.kernel.org, dlemoal@kernel.org, axboe@kernel.dk,
gjoyce@ibm.com
Subject: Re: [PATCHv2 1/6] blk-sysfs: remove q->sysfs_lock for attributes which don't need it
Date: Wed, 19 Feb 2025 06:42:02 +0100 [thread overview]
Message-ID: <20250219054202.GA10395@lst.de> (raw)
In-Reply-To: <Z7VO-z1cZfFLYaMt@fedora>
On Wed, Feb 19, 2025 at 11:24:43AM +0800, Ming Lei wrote:
> On Tue, Feb 18, 2025 at 05:29:53PM +0100, Christoph Hellwig wrote:
> > On Tue, Feb 18, 2025 at 09:45:02PM +0800, Ming Lei wrote:
> > > IMO, this RO attributes needn't protection from q->limits_lock:
> > >
> > > - no lifetime issue
> > >
> > > - in-tree code needn't limits_lock.
> > >
> > > - all are scalar variable, so the attribute itself is updated atomically
> >
> > Except in the memory model they aren't without READ_ONCE/WRITE_ONCE.
>
> RW_ONCE is supposed for avoiding compiler optimization, and scalar
> variable atomic update should be decided by hardware.
Nothing force the compiler to update atomically without that. Yes,
it is very unlikely to get thing wrong, but I'd rather be explicit.
And make sure static and dynamic analysis knows what we are doing here.
next prev parent reply other threads:[~2025-02-19 5:42 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-18 8:28 [PATCHv2 0/6] block: fix lock order and remove redundant locking Nilay Shroff
2025-02-18 8:28 ` [PATCHv2 1/6] blk-sysfs: remove q->sysfs_lock for attributes which don't need it Nilay Shroff
2025-02-18 8:46 ` Christoph Hellwig
2025-02-18 11:26 ` Nilay Shroff
2025-02-21 14:02 ` Nilay Shroff
2025-02-22 12:44 ` Ming Lei
2025-02-24 13:09 ` Nilay Shroff
2025-02-24 14:49 ` Christoph Hellwig
2025-02-26 12:09 ` Nilay Shroff
2025-02-24 8:41 ` Hannes Reinecke
2025-02-24 13:12 ` Nilay Shroff
2025-02-18 12:10 ` Ming Lei
2025-02-18 13:11 ` Nilay Shroff
2025-02-18 13:45 ` Ming Lei
2025-02-18 16:29 ` Christoph Hellwig
2025-02-19 3:24 ` Ming Lei
2025-02-19 5:42 ` Christoph Hellwig [this message]
2025-02-19 8:34 ` Nilay Shroff
2025-02-19 8:56 ` Nilay Shroff
2025-02-19 9:20 ` Ming Lei
2025-02-18 8:28 ` [PATCHv2 2/6] blk-sysfs: acquire q->limits_lock while reading attributes Nilay Shroff
2025-02-18 8:46 ` Christoph Hellwig
2025-02-18 8:28 ` [PATCHv2 3/6] block: Introduce a dedicated lock for protecting queue elevator updates Nilay Shroff
2025-02-18 9:05 ` Christoph Hellwig
2025-02-18 11:14 ` Nilay Shroff
2025-02-18 16:32 ` Christoph Hellwig
2025-02-19 8:41 ` Nilay Shroff
2025-02-18 8:28 ` [PATCHv2 4/6] blk-sysfs: protect nr_requests update using q->elevator_lock Nilay Shroff
2025-02-18 8:28 ` [PATCHv2 5/6] blk-sysfs: protect wbt_lat_usec " Nilay Shroff
2025-02-18 8:28 ` [PATCHv2 6/6] blk-sysfs: protect read_ahead_kb using q->limits_lock Nilay Shroff
2025-02-18 9:12 ` Christoph Hellwig
2025-02-18 11:27 ` Nilay Shroff
2025-02-18 9:21 ` [PATCHv2 0/6] block: fix lock order and remove redundant locking Christoph Hellwig
2025-02-18 12:09 ` Nilay Shroff
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