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From: Jason Gunthorpe <jgg@nvidia.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: alsa-devel@alsa-project.org, Kiran Patil <kiran.patil@intel.com>,
	tiwai@suse.de, ranjani.sridharan@intel.com,
	pierre-louis.bossart@linux.intel.com,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
	Fred Oh <fred.oh@linux.intel.com>,
	broonie@kernel.org, parav@nvidia.com,
	Dave Ertman <david.m.ertman@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Shiraz Saleem <shiraz.saleem@intel.com>,
	Parav Pandit <parav@mellanox.com>
Subject: Re: [PATCH 1/6] Add ancillary bus support
Date: Thu, 1 Oct 2020 11:33:34 -0300	[thread overview]
Message-ID: <20201001143334.GA1103926@nvidia.com> (raw)
In-Reply-To: <20201001121423.GA2375307@kroah.com>

On Thu, Oct 01, 2020 at 02:14:23PM +0200, Greg KH wrote:
> On Thu, Oct 01, 2020 at 08:58:47AM -0300, Jason Gunthorpe wrote:
> > On Thu, Oct 01, 2020 at 01:05:51PM +0200, Greg KH wrote:
> >  
> > > You have to be _VERY_ careful after calling
> > > ancillary_device_initialize(), as now you can not just free up the
> > > memory if something goes wrong before ancillary_device_add() is called,
> > > right?
> > 
> > I've looked at way too many versions of this patch and related. This
> > is the only one so far that I didn't find various bugs on the error
> > cases.
> 
> But you haven't seen the callers of this function.  Without this
> documented, you will have problems.

I've seen the Intel irdma, both versions of the SOF stuff and an
internal mlx5 patch..

Look at the SOF example, it has perfectly paired error unwinds. Each
function has unwind that cleans up exactly what it creates. Every
'free' unwind is paired with an 'alloc' in the same function. Simple.
Easy to audit. Easy to correctly enhance down the road. 

This is the common kernel goto error design pattern.

> Why is this two-step process even needed here?

Initializing the refcount close to the allocation is a common design
pattern as is initializing it close to registration. Both options are
tricky, both have various common subtle bugs, both have awkward
elements.

At the end of the day, after something like 20 iterations, this is the
first series that actually doesn't have error unwind bugs.

Can we empower Dave to make this choice? It is not like it is wild or
weird, the driver core already exposes _initialize and _add functions
that work in exactly the same way.

Jason

  reply	other threads:[~2020-10-01 14:34 UTC|newest]

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-30 22:50 [PATCH 0/6] Ancillary bus implementation and SOF multi-client support Dave Ertman
2020-09-30 22:50 ` [PATCH 1/6] Add ancillary bus support Dave Ertman
2020-09-30 23:05   ` Jason Gunthorpe
2020-10-01 11:01   ` Greg KH
2020-10-01 11:46     ` Jason Gunthorpe
2020-10-01 11:54       ` Greg KH
2020-10-01 12:02         ` Jason Gunthorpe
2020-10-01 12:15           ` Greg KH
2020-10-01 18:26             ` Ertman, David M
2020-10-01 11:02   ` Greg KH
2020-10-01 16:30     ` Ertman, David M
2020-10-01 11:05   ` Greg KH
2020-10-01 11:58     ` Jason Gunthorpe
2020-10-01 12:14       ` Greg KH
2020-10-01 14:33         ` Jason Gunthorpe [this message]
2020-10-01 14:38           ` Greg KH
2020-10-01 16:06             ` Pierre-Louis Bossart
2020-10-01 17:42             ` Jason Gunthorpe
2020-10-01 14:39           ` Parav Pandit
2020-10-01 14:43             ` Greg KH
2020-10-01 13:27   ` Mark Brown
2020-09-30 22:50 ` [PATCH 2/6] ASoC: SOF: Introduce descriptors for SOF client Dave Ertman
2020-10-01 13:02   ` Greg KH
2020-10-01 15:59     ` Sridharan, Ranjani
2020-10-01 22:16     ` Sridharan, Ranjani
2020-10-02  4:53       ` gregkh
2020-10-02 17:07         ` Sridharan, Ranjani
2020-10-03  9:02           ` gregkh
2020-10-05  2:35             ` Sridharan, Ranjani
2020-10-05 11:27               ` gregkh
2020-10-05 15:18                 ` Pierre-Louis Bossart
2020-10-05 15:32                   ` gregkh
2020-10-01 13:38   ` Mark Brown
2020-10-01 16:48     ` Sridharan, Ranjani
2020-09-30 22:50 ` [PATCH 3/6] ASoC: SOF: Create client driver for IPC test Dave Ertman
2020-10-01 13:04   ` Greg KH
2020-10-01 16:46     ` Sridharan, Ranjani
2020-10-01 13:09   ` Greg KH
2020-10-01 13:55     ` Pierre-Louis Bossart
2020-10-01 16:48       ` Ertman, David M
2020-10-01 13:59   ` Mark Brown
2020-09-30 22:50 ` [PATCH 4/6] ASoC: SOF: ops: Add ops for client registration Dave Ertman
2020-09-30 22:50 ` [PATCH 5/6] ASoC: SOF: Intel: Define " Dave Ertman
2020-09-30 22:50 ` [PATCH 6/6] ASoC: SOF: debug: Remove IPC flood test support in SOF core Dave Ertman
2020-10-01  5:58 ` [PATCH 0/6] Ancillary bus implementation and SOF multi-client support Greg KH
2020-10-01 15:54   ` Ertman, David M
2020-10-01  7:14 ` Greg KH
2020-10-01 15:55   ` Ertman, David M
2020-10-01 16:10     ` Greg KH
2020-10-01 17:13       ` Ertman, David M
2020-10-02 20:23   ` Ertman, David M
2020-10-03  9:08     ` Greg KH
2020-10-03  9:09       ` Greg KH
2020-10-04  2:26       ` Parav Pandit
2020-10-04 23:45       ` Williams, Dan J
2020-10-05  1:18         ` Ertman, David M
2020-10-05  2:39           ` Parav Pandit
2020-10-05 11:25         ` gregkh
2020-10-06 22:40           ` Dan Williams
2020-10-07  9:14             ` gregkh
2020-10-07 16:19               ` Dan Williams
2020-10-07 16:22                 ` Mark Brown
2020-10-07 16:41                   ` Dan Williams
2020-10-07 16:42                   ` Pierre-Louis Bossart
2020-10-07 16:56                     ` Parav Pandit
2020-10-01 10:05 ` Rojewski, Cezary
2020-10-01 10:59   ` gregkh
2020-10-01 12:49     ` Jason Gunthorpe
2020-10-01 12:55       ` gregkh
2020-10-01 13:26         ` Jason Gunthorpe
2020-10-01 14:17           ` gregkh
2020-10-01 15:08         ` Parav Pandit
2020-10-01 12:50 ` Mark Brown
2020-10-01 13:12   ` Greg KH
2020-10-01 13:42     ` Jason Gunthorpe
2020-10-01 14:40     ` Mark Brown
2020-10-01 15:32       ` Greg KH
2020-10-01 16:03         ` Mark Brown
2020-10-01 18:16           ` Greg KH
2020-10-01 18:29             ` Ertman, David M
2020-10-01 19:38               ` Mark Brown
2020-10-01 19:54                 ` Ertman, David M
2020-10-01 20:17                   ` Mark Brown
2020-10-02  0:47                     ` Jason Gunthorpe
2020-10-02 11:19                       ` Mark Brown
2020-10-02 17:23                         ` Ertman, David M
2020-10-02 17:25                           ` Jason Gunthorpe
2020-10-02 17:44                             ` Mark Brown
2020-10-01 14:07   ` Pierre-Louis Bossart
2020-10-01 15:24     ` Mark Brown
2020-10-01 16:20       ` Pierre-Louis Bossart
2020-10-01 16:51         ` Mark Brown
2020-10-01 18:04           ` Jason Gunthorpe
2020-10-01 18:13             ` Greg KH
2020-10-01 19:23             ` Mark Brown
2020-10-01 16:50     ` Ertman, David M
2020-10-01 17:10       ` Mark Brown
2020-10-01 17:16         ` Ertman, David M
2020-10-01 17:52 ` Ertman, David M

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