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From: Greg KH <gregkh@linuxfoundation.org>
To: David Howells <dhowells@redhat.com>
Cc: viro@zeniv.linux.org.uk, raven@themaw.net,
	linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-block@vger.kernel.org, keyrings@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] General notification queue with user mmap()'able ring buffer
Date: Wed, 29 May 2019 16:11:12 -0700	[thread overview]
Message-ID: <20190529231112.GB3164@kroah.com> (raw)
In-Reply-To: <31936.1559146000@warthog.procyon.org.uk>

On Wed, May 29, 2019 at 05:06:40PM +0100, David Howells wrote:
> Greg KH <gregkh@linuxfoundation.org> wrote:
> > And how does the tracing and perf ring buffers do this without needing
> > volatile?  Why not use the same type of interface they provide, as it's
> > always good to share code that has already had all of the nasty corner
> > cases worked out.
> 
> I've no idea how trace does it - or even where - or even if.  As far as I can
> see, grepping for mmap in kernel/trace/*, there's no mmap support.
> 
> Reading Documentation/trace/ring-buffer-design.txt the trace subsystem has
> some sort of transient page fifo which is a lot more complicated than what I
> want and doesn't look like it'll be mmap'able.
> 
> Looking at the perf ring buffer, there appears to be a missing barrier in
> perf_aux_output_end():
> 
> 	rb->user_page->aux_head = rb->aux_head;
> 
> should be:
> 
> 	smp_store_release(&rb->user_page->aux_head, rb->aux_head);
> 
> It should also be using smp_load_acquire().  See
> Documentation/core-api/circular-buffers.rst
> 
> And a (partial) patch has been proposed: https://lkml.org/lkml/2018/5/10/249

So, if that's all that needs to be fixed, can you use the same
buffer/code if that patch is merged?

thanks,

greg k-h

  parent reply	other threads:[~2019-05-29 23:11 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-28 16:01 [RFC][PATCH 0/7] Mount, FS, Block and Keyrings notifications David Howells
2019-05-28 16:01 ` [PATCH 1/7] General notification queue with user mmap()'able ring buffer David Howells
2019-05-28 16:26   ` Greg KH
2019-05-28 17:30   ` David Howells
2019-05-28 23:12     ` Greg KH
2019-05-29 16:06     ` David Howells
2019-05-29 17:46       ` Jann Horn
2019-05-29 21:02       ` David Howells
2019-05-31 11:14         ` Peter Zijlstra
2019-05-31 12:02         ` David Howells
2019-05-31 13:26           ` Peter Zijlstra
2019-05-31 14:20           ` David Howells
2019-05-31 16:44             ` Peter Zijlstra
2019-05-31 17:12             ` David Howells
2019-06-17 16:24               ` Peter Zijlstra
2019-05-29 23:09       ` Greg KH
2019-05-29 23:11       ` Greg KH [this message]
2019-05-30  9:50         ` Andrea Parri
2019-05-31  8:35           ` Peter Zijlstra
2019-05-31  8:47       ` Peter Zijlstra
2019-05-31 12:42       ` David Howells
2019-05-31 14:55       ` David Howells
2019-05-28 19:14   ` Jann Horn
2019-05-28 22:28   ` David Howells
2019-05-28 23:16     ` Jann Horn
2019-05-28 16:02 ` [PATCH 2/7] keys: Add a notification facility David Howells
2019-05-28 16:02 ` [PATCH 3/7] vfs: Add a mount-notification facility David Howells
2019-05-28 20:06   ` Jann Horn
2019-05-28 23:04   ` David Howells
2019-05-28 23:23     ` Jann Horn
2019-05-29 11:16     ` David Howells
2019-05-28 23:08   ` David Howells
2019-05-29 10:55   ` David Howells
2019-05-29 11:00   ` David Howells
2019-05-29 15:53     ` Casey Schaufler
2019-05-29 16:12       ` Jann Horn
2019-05-29 17:04         ` Casey Schaufler
2019-06-03 16:30         ` David Howells
2019-05-29 17:13       ` Andy Lutomirski
2019-05-29 17:46         ` Casey Schaufler
2019-05-29 18:11           ` Jann Horn
2019-05-29 19:28             ` Casey Schaufler
2019-05-29 19:47               ` Jann Horn
2019-05-29 20:50                 ` Casey Schaufler
2019-05-29 23:12           ` Andy Lutomirski
2019-05-29 23:56             ` Casey Schaufler
2019-05-28 16:02 ` [PATCH 4/7] vfs: Add superblock notifications David Howells
2019-05-28 20:27   ` Jann Horn
2019-05-29 12:58   ` David Howells
2019-05-29 14:16     ` Jann Horn
2019-05-28 16:02 ` [PATCH 5/7] fsinfo: Export superblock notification counter David Howells
2019-05-28 16:02 ` [PATCH 6/7] block: Add block layer notifications David Howells
2019-05-28 20:37   ` Jann Horn
2019-05-28 16:02 ` [PATCH 7/7] Add sample notification program David Howells
2019-05-28 23:58 ` [RFC][PATCH 0/7] Mount, FS, Block and Keyrings notifications Greg KH
2019-05-29  6:33 ` Amir Goldstein
2019-05-29 14:25   ` Jan Kara
2019-05-29 15:10     ` Greg KH
2019-05-29 15:53     ` Amir Goldstein
2019-05-30 11:00       ` Jan Kara
2019-06-04 12:33     ` David Howells
2019-05-29  6:45 ` David Howells
2019-05-29  7:40   ` Amir Goldstein
2019-05-29  9:09 ` David Howells
2019-05-29 15:41   ` Casey Schaufler

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