Message-ID: <1374006725.12825.112.camel@envy.home>
Date:	Tue, 16 Jul 2013 13:32:05 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	netdev@...r.kernel.org
Subject: Re: [RFC] Any value in having a netdev FAQ?

On Mon, 2013-07-15 at 22:59 -0400, Paul Gortmaker wrote:
> Hi Dave,
> 
> I was wondering if you think there is value in having a netdev-faq type
> document available -- perhaps as a vger mailout to new subscribers or
> similar?  For example, I have lost count of the number of times that you
> have had to tell people that net-next is closed during the merge window.
> But you would probably be right in telling me that those same people don't
> read documentation.  Well, that aside, I suppose answering my question
> is easier when there is a proposed starting point for content.
> 
> To that end, I've tried to collect a starting point based on repeated
> questions/corrections that I've seen over the years.  I've added Greg to
> the Cc: in order to ensure I've captured the netdev-stable interaction
> correctly, and I've thrown Darren under the bus as a random content
> reviewer, since he has expressed an interest in documentation recently.

And I'm going to learn how to properly interract on netdev while I'm at
it.  It's a win win :-)

> 
> Below is a possible starting point for content.  Many answers I have
> written are from memory, long after losing links to netdev threads that
> served as evidence for the answers, so apologies in advance if I have
> failed to recall correctly the specific details in which you would like
> to see things done.
> 
> Thanks,
> Paul.
> --
> 
> Information you need to know about netdev
> -----------------------------------------
> 
> Q: What is netdev?
> 
> A: It is a mailing list for all network related linux stuff.  This includes
>    anything found under net/  (i.e. core code like IPv6) and drivers/net
>    (i.e. hardware specific drivers) in the linux source tree.
> 
>    Note that some subsystems (e.g. wireless drivers) which have a high volume
>    of traffic have their own specific mailing lists.
> 
>    The netdev list is managed (like many other linux mailing lists) through
>    VGER ( http://vger.kernel.org/ ) and archives can be found below:
> 
> 	http://marc.info/?l=linux-netdev
> 	http://www.spinics.net/lists/netdev/
> 
>    Aside from subsystems like that mentioned above, all network related linux
>    development (i.e. RFC, review, comments, etc) takes place on netdev.
> 


Should LKML be Cc'd? I assume so...


> Q: How do the changes posted to netdev make their way into linux?
> 
> A: There are always two trees (git repositories) in play.  Both are driven
>    by David Miller, the main network maintainer.  There is the "net" tree,
>    and the "net-next" tree.  As you can probably guess from the names, the
>    net tree is for fixes to existing code already in the mainline tree from
>    Linus, and net-next is where the new code goes for the future release.
>    You can find the trees here:
> 
> 	http://git.kernel.org/?p=linux/kernel/git/davem/net.git
> 	http://git.kernel.org/?p=linux/kernel/git/davem/net-next.git
> 
> Q: How often do changes from these trees make it to the mainline Linus tree?
> 
> A: To understand this, you need to know a bit of background information
>    on the cadence of linux development.  Each new release starts off with
>    a two week "merge window" where the main maintainers feed their new
>    stuff to Linus for merging into the mainline tree.  After the two weeks,
>    the merge window is closed, and it is called/tagged "-rc1".  No new
>    features get mainlined after this -- only fixes to the rc1 content
>    are expected.  After roughly a week of collecting fixes to the rc1
>    content, rc2 is released.  This repeats on a roughly weekly basis
>    until rc7 (typically; sometimes rc6 if things are quiet, or rc8 if
>    things are in a state of churn), and a week after the last vX.Y-rcN
>    was done, the official "vX.Y" is released.
> 
>    Relating that to netdev:  At the beginning of the 2wk merge window,


Best not to abbreviate, we can spare the 3 bytes for " week" :-)


>    the net-next tree will be closed - no new changes/features.  The
>    accumulated new content of the past ~10 weeks will be passed onto
>    mainline/Linus via a pull request for vX.Y -- at the same time,
>    the "net" tree will start accumulating fixes for this pulled content
>    relating to vX.Y
> 
>    An announcement indicating when net-next has been closed is usually
>    sent to netdev, but knowing the above, you can predict that in advance.
> 
>    IMPORTANT:  Do not send new net-next content to netdev during the
>    period during which net-next tree is closed.


It would be handy to have a netdev-next bot that responded to "~/^
\[PATCH/" email (off list) during the merge window with a reminder of
this point. Not everyone is active enough in kernel development be
always aware of where we are in the cycle. Greg has a bot deal with
common mistakes, so there is precedent.


> 
>    Shortly after the two weeks have passed, (and vX.Y-rc1 is released) the
>    tree for net-next reopens to collect content for the next (vX.Y+1) release.
> 
>    The "net" tree continues to collect fixes for the vX.Y content, and
>    is fed back to Linus at regular (~weekly) intervals.  Meaning that the
>    focus for "net" is on stablilization and bugfixes.
> 
>    Finally, the vX.Y gets released, and the whole cycle starts over.
> 
> Q: So where are we now in this cycle?
> 
> A: Load the mainline (Linus) page here:
> 
> 	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git
> 
>    and note the top of the "tags" section.  If it is rc1, it is early
>    in the dev cycle.  If it was tagged rc7 a week ago, then a release
>    is probably imminent.
> 


How does one determine if we are in the merge window? I wonder if we
could have DEV_CYCLE file in the linux git repository which read:

MERGE WINDOW
BUG FIX ONLY (-rc1+)
CRITICAL FIXES ONLY (-rc4+)

That would make it trivial to know from right there in the sources where
we are.


> Q: How do I indicate which tree (net vs. net-next) my patch should be in?
> 
> A: Firstly, think whether you have a bug fix or new "next-like" content.
>    Then once decided, assuming that you use git, use the prefix flag, i.e.
> 
> 	git format-patch --subject-prefix='PATCH net-next' start..finish
> 
>    Use "net" instead of "net-next" in the above for bug-fix net content.
>    If you don't use git, then note the only magic in the above is just
>    the subject text of the outgoing e-mail, and you can manually change
>    it yourself with whatever MUA you are comfortable with.
> 
> Q: I sent a patch and I'm wondering what happened to it.  How can I tell
>    whether it got merged?
> 
> A: Start by looking at the main patchworks queue for netdev:
> 
> 	http://patchwork.ozlabs.org/project/netdev/list/
> 
>    The "State" field will tell you exactly where things are at with
>    your patch.
> 
> Q: The above only says "Under Review".  How can I find out more?
> 
> A: Generally speaking, the patches get triaged quickly (in less than 48h).
>    So be patient.  Asking the maintainer for status updates on your
>    patch is a good way to ensure your patch is ignored or pushed to
>    the bottom of the priority list.
> 
> Q: How can I tell what patches are queued up for backporting to the 
>    various stable releases?
> 
> A: Normally Greg Kroah-Hartman collects stable commits himself, but
>    for networking, Dave collects up patches he deems critical for the
>    networking subsystem, and then hands them off to Greg.
> 
>    There is a patchworks queue that you can see here:
> 	http://patchwork.ozlabs.org/bundle/davem/stable/?state=*
> 
>    It contains the patches which Dave has selected, but not yet handed
>    off to Greg.  If Greg already has the patch, then it will be here:
> 	http://git.kernel.org/cgit/linux/kernel/git/stable/stable-queue.git
> 
>    A quick way to find whether the patch is in this stable-queue is
>    to simply clone the repo, and then git grep the mainline commit ID, e.g.
> 
> 	stable-queue$ git grep -l 284041ef21fdf2e
> 	releases/3.0.84/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
> 	releases/3.4.51/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
> 	releases/3.9.8/ipv6-fix-possible-crashes-in-ip6_cork_release.patch
> 	stable/stable-queue$ 
> 


This needs a reference to stable_kernel_rules.txt IMO, and possibly less
content here.


> Q: I see a network patch and I think it should be backported to stable.
>    Should I request it via "stable@...r.kernel.org" like the references in
>    the kernel's Documentation/ directory say?

stable_kernel_rules.txt specifically

> 
> A: No, not for networking.  Check the stable queues as per above 1st to see
>    if it is already queued.  If not, then send a mail to netdev, listing
>    the upstream commit ID and why you think it should be a stable candidate.


I had no idea as an infrequent contributor to netdev!
stable_kernel_rules.txt needs some exceptions noted and a reference to
this.


> 
>    Before you jump to go do the above, do note that the normal stable rules
>    in Documentation/stable_kernel_rules.txt still apply.  So you need to 
>    explicitly indicate why it is a critical fix and exactly what users are
>    impacted.  In addition, you need to convince yourself that you _really_
>    think it has been overlooked, vs. having been considered and rejected.
> 
>    Generally speaking, the longer it has had a chance to "soak" in mainline,
>    the better the odds that it is an OK candidate for stable.  So scrambling
>    to request a commit be added the day after it appears should be avoided.
> 
> Q: I have created a network patch and I think it should be backported to
>    stable.  Should I add a "Cc: stable@...r.kernel.org" like the references
>    in the kernel's Documentation/ directory say?
> 
> A: No.  See above answer.  In short, if you think it really belongs in
>    stable, then ensure you write a decent commit log that describes who
>    gets impacted by the bugfix and how it manifests itself, and when the
>    bug was introduced.  If you do that properly, then the commit will
>    get handled appropriately and most likely get put in the patchworks
>    stable queue if it really warrants it.
> 
>    If you think there is some valid information relating to it being in
>    stable that does _not_ belong in the commit log, then use the three
>    dash marker line as described in Documentation/SubmittingPatches to 
>    temporarily embed that information into the patch that you send.
> 
> Q: Someone said that the comment style and coding convention is different
>    for the networing content.  Is this true?


networking

> 
> A: Yes, in a largely trivial way.  Instead of this:
> 
> 	/*
> 	 * foobar blah blah blah
> 	 * another line of text
> 	 */
> 
>    it is requested that you make it look like this:
> 
> 	/* foobar blah blah blah
> 	 * another line of text
> 	 */


This is.... unfortunate. I see the warnings from checkpatch.pl and I
have to choose between adhering to that or keeping a file which is in
complete violation to that consistent. I risk flaming either way.

Do we really need different coding styles for different sub directories
of the same source tree? I won't say anything more on this or try to
argue the point, it isn't my call. Just seems.... strange to me.


> 
> Q: I am working in existing code that has the former comment style and not the
>    latter.  Should I submit new code in the former style or the latter?
> 
> A: Make it the latter style, so that eventually all code in the domain of
>    netdev is of this format.


:-) OK


> 
> Q: I found a bug that might have possible security implications or similar.
>    Should I mail the main netdev maintainer off-list?
> 
> A: No. The current netdev maintainer has consistently requested that people
>    use the mailing lists and not reach out directly.  If you aren't OK with
>    that, then perhaps consider using "security@...nel.org" instead.
> 
> Q: What level of testing is expected before I submit my change?
> 
> A: If your changes are against net-next, then the expectation is that

s/then//

>    you have tested by layering your changes on top of net-next.  Ideally
>    you will have done run-time testing specific to your change, but
>    at a minimum, your changes should survive an "allyesconfig" and an
>    "allmodconfig" build without new warnings or failures.
> 
> Q: Any other tips to help ensure my net/net-next patch gets OK'd?
> 
> A: Attention to detail.  You can start with checkpatch.pl, but do not
>    be mindlessly robotic in doing so.  Re-read your own work as if you were
>    the reviewer.  If your change is a bug-fix, make sure your commit log
>    indicates the end-user visible symptom, the underlying reason as
>    to why it happens, and then if necessary, explain why the fix proposed
>    is the best way to get things done.   Don't mangle whitespace, and as
>    is common, don't mis-indent function arguments that span multiple lines.


This needs a reference to SubmittingPatches

This is great Paul, thank you for taking the time.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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