DPDK-dev Archive on lore.kernel.org
 help / color / Atom feed
From: Neil Horman <nhorman@tuxdriver.com>
To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
Cc: Bruce Richardson <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [EXT] [RFC PATCH 0/2] introduce __rte_internal tag
Date: Thu, 6 Jun 2019 09:35:03 -0400
Message-ID: <20190606133503.GB29521@hmswarspite.think-freely.org> (raw)
In-Reply-To: <BYAPR18MB242407B0A2A21E187843917FC8170@BYAPR18MB2424.namprd18.prod.outlook.com>

On Thu, Jun 06, 2019 at 12:04:57PM +0000, Jerin Jacob Kollanukkaran wrote:
> > -----Original Message-----
> > From: Neil Horman <nhorman@tuxdriver.com>
> > Sent: Thursday, June 6, 2019 5:04 PM
> > To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
> > Cc: Bruce Richardson <bruce.richardson@intel.com>; dev@dpdk.org;
> > Thomas Monjalon <thomas@monjalon.net>
> > Subject: Re: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag
> > 
> > On Thu, Jun 06, 2019 at 09:44:52AM +0000, Jerin Jacob Kollanukkaran wrote:
> > > > -----Original Message-----
> > > > From: Neil Horman <nhorman@tuxdriver.com>
> > > > Sent: Wednesday, June 5, 2019 11:41 PM
> > > > To: Bruce Richardson <bruce.richardson@intel.com>
> > > > Cc: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; dev@dpdk.org;
> > > > Thomas Monjalon <thomas@monjalon.net>
> > > > Subject: Re: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag
> > > >
> > > > On Wed, Jun 05, 2019 at 05:45:41PM +0100, Bruce Richardson wrote:
> > > > > On Wed, Jun 05, 2019 at 04:24:09PM +0000, Jerin Jacob
> > > > > Kollanukkaran
> > > > wrote:
> > > > > > > -----Original Message-----
> > > > > > > From: Neil Horman <nhorman@tuxdriver.com>
> > > > > > > Sent: Sunday, May 26, 2019 12:14 AM
> > > > > > > To: dev@dpdk.org
> > > > > > > Cc: Neil Horman <nhorman@tuxdriver.com>; Jerin Jacob
> > > > > > > Kollanukkaran <jerinj@marvell.com>; Bruce Richardson
> > > > > > > <bruce.richardson@intel.com>; Thomas Monjalon
> > > > > > > <thomas@monjalon.net>
> > > > > > > Subject: [EXT] [RFC PATCH 0/2] introduce __rte_internal tag
> > > > > > >
> > > > > > > Hey-
> > > > > > > 	Based on our recent conversations regarding the use of
> > > > > > > symbols only meant for internal dpdk consumption (between dpdk
> > > > > > > libraries), this is an idea that I've come up with that I'd
> > > > > > > like to get some feedback on
> > > > > > >
> > > > > > > Summary:
> > > > > > > 1) We have symbols in the DPDK that are meant to be used
> > > > > > > between DPDK libraries, but not by applications linking to
> > > > > > > them
> > > > > > > 2) We would like to document those symbols in the code, so as
> > > > > > > to note them clearly as for being meant for internal use only
> > > > > > > 3) Linker symbol visibility is a very coarse grained tool, and
> > > > > > > so there is no good way in a single library to mark items as
> > > > > > > being meant for use only by other DPDK libraries, at least not
> > > > > > > without some extensive runtime checking
> > > > > > >
> > > > > > >
> > > > > > > Proposal:
> > > > > > > I'm proposing that we introduce the __rte_internal tag.  From
> > > > > > > a coding standpoint it works a great deal like the
> > > > > > > __rte_experimental tag in that it expempts the tagged symbol
> > > > > > > from ABI constraints (as the only users should be represented
> > > > > > > in the DPDK build environment).  Additionally, the
> > > > > > > __rte_internal macro resolves differently based on the
> > > > > > > definition of the BUILDING_RTE_SDK flag (working under the
> > > > > > > assumption that said flag should only ever be set if we are
> > > > > > > actually building DPDK libraries which will make use of
> > > > > > > internal calls).  If the BUILDING_RTE_SDK flag is set
> > > > > > > __rte_internal resolves to __attribute__((section
> > > > > > > "text.internal)), placing it in a special text section which
> > > > > > > is then used to validate that the the symbol appears in the
> > > > > > > INTERNAL section of the corresponding library version map).
> > > > > > > If BUILDING_RTE_SDK is not set, then __rte_internal resolves
> > > > > > > to
> > > > __attribute__((error("..."))), which causes any caller of the tagged
> > > > function to throw an error at compile time, indicating that the
> > > > symbol is not available for external use.
> > > > > > >
> > > > > > > This isn't a perfect solution, as applications can still hack
> > > > > > > around it of course,
> > > > > >
> > > > > > I think, one way to, avoid, hack around could be to,
> > > > > >
> > > > > > 1) at config stage, create  a random number for the build
> > > > > > 2) introduce RTE_CALL_INTERNAL macro for calling internal
> > > > > > function, compare the generated random number for allowing the
> > > > > > calls to make within the library. i.e leverage the fact that
> > > > > > external library would never know the random number generated
> > > > > > for the DPDK build
> > > > and internal driver code does.
> > > > > >
> > > > > Do we really need to care about this. If have some determined
> > > > > enough to hack around our limitations, then they surely know that
> > > > > they have an unsupported configuration. We just need to protect
> > > > > against inadvertent use of internals, IMHO.
> > > > >
> > > > I agree, I too had thought about doing some sort of internal runtime
> > > > checking to match internal only symbols, such that they were only
> > > > accessable by internally approved users, but it started to feel like a great
> > deal of overhead.
> > > > Its a good idea for a general mechanism I think, but I believe the
> > > > value here is more to internally document which apis we want to mark
> > > > as being for internal use only, and create a lightweight roadblock
> > > > at build time to catch users inadvertently using them.  Determined
> > > > users will get around anything, and theres not much we can do to stop
> > them.
> > >
> > > I agree too. IMHO, Simply having following items would be enough
> > >
> > > 1) Avoid exposing the internal function prototype through public
> > > header files
> > > 2) Add @internal to API documentation
> > > 3) Just decide the name space for internal API for tooling(i.e not
> > > start with rte_ or so) Using objdump scheme to detect internal functions
> > requires the the library to build prior to run the checkpatch.
> > >
> > 
> > No, I'm not comfortable with that approach, and I've stated why:
> > 1) Not exposing the functions via header files is a fine start
> > 
> > 2) Adding internal documentation is also fine, but does nothing to correlate
> > the code implementing those functions to the documentation.  Its valuable
> > to have a tag on a function identifying it as internal only.
> > 
> > 3) Using naming conventions to separate internal only from non-internal
> > functions is a vague approach, requiring future developers to be cogniscent
> > of the convention and make the appropriate naming choices.  It also implicitly
> > restricts the abliity for future developers to make naming changes in conflict
> > with that convention
> 
> Enforcing the naming convention can be achieved through tooling as well.
> 
Sure, but why enforce any function naming at all, when you don't have to.

> > 
> > 4) Adding a tag like __rte_internal creates an interlock whereby, not only are
> > internal functions excused from ABI constraints, but forces developers to
> > intentionally mark their internal functions as being internal in the code, which
> > is beneficial to clarlity of understanding during the development process.
> 
> No issues in adding __rte_internal. But, I am against current implementaion, 
> Ie. adding objdump dependency
That dependency already exists for the __rte_external flag

> to checkpatch i.e developer has to build the library first so  that checkpatch can
> can know, Is it belongs to internal section or not?
> 
What developer is running checkpatch/posting patches without first building
their changes?


> > 
> > 5) Adding a tag like __rte_internal is explicit, and allows developers to use a
> > single header file instead of multiple header files if they so choose
> > 
> > We went through this with experimental symbols as well[1], and it just
> > makes more sense to me to clearly document in the code what constitutes
> > an internal symbol rather than relying on naming conventions and hoping
> > that developers read the documentation before exporting a symbol
> > publically.
> > 
> > 
> > [1] https://mails.dpdk.org/archives/dev/2017-December/083828.html
> > > >
> > > > If we really wanted to go down that road, we could use a mechainsm
> > > > simmilar to the EXPORT_SYMBOL / EXPORT_SYMBOL_GPL infrastructure
> > > > that the kernel uses, but that would required building our own
> > > > custom linker script, which seems like overkill here.
> > > >
> > > > Best
> > > > Neil
> > > >
> > > > > /Bruce
> > > > >
> > >
> 

  parent reply index

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-25 18:43 [dpdk-dev] " Neil Horman
2019-05-25 18:43 ` [dpdk-dev] [RFC PATCH 1/2] Add __rte_internal tag for functions and version target Neil Horman
2019-06-05 16:14   ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-05-25 18:43 ` [dpdk-dev] [RFC PATCH 2/2] Convert dpaa driver to tag internal-only symbols appropriately Neil Horman
2019-06-05 16:24 ` [dpdk-dev] [EXT] [RFC PATCH 0/2] introduce __rte_internal tag Jerin Jacob Kollanukkaran
2019-06-05 16:45   ` Bruce Richardson
2019-06-05 18:11     ` Neil Horman
2019-06-06  9:44       ` Jerin Jacob Kollanukkaran
2019-06-06 11:34         ` Neil Horman
2019-06-06 12:04           ` Jerin Jacob Kollanukkaran
2019-06-06 13:18             ` Wiles, Keith
2019-06-06 13:43               ` Neil Horman
2019-06-06 13:53                 ` Wiles, Keith
2019-06-06 14:46                   ` Neil Horman
2019-06-06 13:35             ` Neil Horman [this message]
2019-06-06 14:02               ` Jerin Jacob Kollanukkaran
2019-06-06 15:03                 ` Neil Horman
2019-06-06 15:14                   ` Jerin Jacob Kollanukkaran
2019-06-06 15:26                     ` Neil Horman
2019-06-06 16:23                       ` Jerin Jacob Kollanukkaran
2019-06-06 16:55                         ` Neil Horman
2019-06-07  9:41                           ` Jerin Jacob Kollanukkaran
2019-06-07 10:35                             ` Neil Horman
2019-06-07 15:42                   ` Ray Kinsella
2019-06-07 18:21                     ` Wiles, Keith
2019-06-12 20:38 ` [dpdk-dev] [PATCH v1 0/9] dpdk: " Neil Horman
2019-06-12 20:38   ` [dpdk-dev] [PATCH v1 1/9] Add __rte_internal tag for functions and version target Neil Horman
2019-06-12 20:38   ` [dpdk-dev] [PATCH v1 2/9] Exempt INTERNAL symbols from checking Neil Horman
2019-06-12 20:38   ` [dpdk-dev] [PATCH v1 3/9] mark dpaa driver internal-only symbols with __rte_internal Neil Horman
2019-06-12 20:38   ` [dpdk-dev] [PATCH v1 4/9] fslmc: identify internal only functions and tag them as __rte_internal Neil Horman
2019-06-12 20:38   ` [dpdk-dev] [PATCH v1 5/9] dpaa2: Adjust dpaa2 driver to mark internal symbols with __rte_internal Neil Horman
2019-06-12 20:39   ` [dpdk-dev] [PATCH v1 6/9] dpaax: mark internal functions " Neil Horman
2019-06-12 20:39   ` [dpdk-dev] [PATCH v1 7/9] cpt: " Neil Horman
2019-06-17  5:27     ` [dpdk-dev] [EXT] " Anoob Joseph
2019-06-12 20:39   ` [dpdk-dev] [PATCH v1 8/9] octeonx: " Neil Horman
2019-06-12 20:39   ` [dpdk-dev] [PATCH v1 9/9] dpaa2: " Neil Horman
2019-06-12 21:14     ` Aaron Conole
2019-06-13 10:24       ` Neil Horman
2019-06-13  7:53   ` [dpdk-dev] [PATCH v1 0/9] dpdk: introduce __rte_internal tag David Marchand
2019-06-13 10:30     ` Neil Horman
2019-06-13 14:23 ` [dpdk-dev] [PATCH v2 0/10] " Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 01/10] Add __rte_internal tag for functions and version target Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 02/10] meson: add BUILDING_RTE_SDK Neil Horman
2019-06-13 14:44     ` Bruce Richardson
2019-06-19 10:39       ` Neil Horman
2019-06-19 10:46         ` Bruce Richardson
2019-06-19 18:34           ` Neil Horman
2019-06-20 10:20             ` Bruce Richardson
2019-06-20 10:21     ` Bruce Richardson
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 03/10] Exempt INTERNAL symbols from checking Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 04/10] mark dpaa driver internal-only symbols with __rte_internal Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 05/10] fslmc: identify internal only functions and tag them as __rte_internal Neil Horman
2019-06-17  7:30     ` Hemant Agrawal
2019-06-19 10:45       ` Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 06/10] dpaa2: Adjust dpaa2 driver to mark internal symbols with __rte_internal Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 07/10] dpaax: mark internal functions " Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 08/10] cpt: " Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 09/10] octeonx: " Neil Horman
2019-06-13 14:23   ` [dpdk-dev] [PATCH v2 10/10] dpaa2: " Neil Horman
2019-08-06 10:03   ` [dpdk-dev] [PATCH v2 0/10] dpdk: introduce __rte_internal tag Thomas Monjalon
2019-08-06 12:21     ` Neil Horman

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190606133503.GB29521@hmswarspite.think-freely.org \
    --to=nhorman@tuxdriver.com \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=jerinj@marvell.com \
    --cc=thomas@monjalon.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK-dev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dpdk-dev/0 dpdk-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dpdk-dev dpdk-dev/ https://lore.kernel.org/dpdk-dev \
		dev@dpdk.org dpdk-dev@archiver.kernel.org
	public-inbox-index dpdk-dev


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/ public-inbox