Linux-NVDIMM Archive on lore.kernel.org
 help / color / Atom feed
From: Petr Mladek <pmladek@suse.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: brakmo@fb.com, Brendan Higgins <brendanhiggins@google.com>,
	dri-devel@lists.freedesktop.org, linux-kselftest@vger.kernel.org,
	shuah@kernel.org, robh@kernel.org, frowand.list@gmail.com,
	linux-nvdimm@lists.01.org, richard@nod.at, knut.omang@oracle.com,
	kieran.bingham@ideasonboard.com, joel@jms.id.au,
	Tim.Bird@sony.com, jdike@addtoit.com, keescook@google.com,
	linux-um@lists.infradead.org, rostedt@goodmis.org,
	julia.lawall@lip6.fr, kunit-dev@googlegroups.com,
	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
	daniel@ffwll.ch, mpe@ellerman.id.au, joe@perches.com,
	khilman@baylibre.com
Subject: Re: [RFC v3 03/19] kunit: test: add string_stream a std::stream like string builder
Date: Mon, 3 Dec 2018 11:55:17 +0100
Message-ID: <20181203105517.vbedwygttxxbdtan@pathway.suse.cz> (raw)
In-Reply-To: <20181130032924.GH18410@garbanzo.do-not-panic.com>

On Thu 2018-11-29 19:29:24, Luis Chamberlain wrote:
> On Wed, Nov 28, 2018 at 11:36:20AM -0800, Brendan Higgins wrote:
> > A number of test features need to do pretty complicated string printing
> > where it may not be possible to rely on a single preallocated string
> > with parameters.
> > 
> > So provide a library for constructing the string as you go similar to
> > C++'s std::string.
> 
> Hrm, what's the potential for such thing actually being eventually
> generically useful for printk folks, I wonder? Petr?

printk() is a bit tricky:

   + It should work in any context. Any additional lock adds risk of a
     deadlock. Especially the NMI and scheduler contexts are problematic.
     There are problems with any other code that might be called
     from console drivers and calls printk() under a lock.

   + It should work also when the system is out of memory. Especially
     atomic context is problematic because we could not wait for
     memory reclaim or swap.

   + We also do to the best effort to get the message out on the
     console. It is important when the system is about to die.
     Any extra buffering layer might cause delay and avoid seeing the
     message.

>From this point of views, this API is not generally usable with printk().

Now, the question is how many of the above fits also for unit testing.
At least, you might need to be careful when allocating memory in
atomic context.

BTW: There are more existing printk APIs: Well, I admit the they are
not easily reusable in unit testing:

   + printk() is old, crappy code, complicated with all the
     cornercases and consoles.

   + include/linux/seq_buf.h is simple buffering. It is used primary
     for sysfs output. It might be usable if you add support for
     loglevel and use big enough buffer. I quess that you should
     flush the buffer regularly anyway.

   + trace_printk() uses lockless per-CPU buffers. It currently does not
     support loglevels. But it might be pretty interesting choice as well.


I do not say that you have to use one of the existing API. But you
might consider them if you encouter any problems and maintaining
your variant gets complicated.

Best Regards,
Petr
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

  parent reply index

Thread overview: 118+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-28 19:36 [RFC v3 00/19] kunit: introduce KUnit, the Linux kernel unit testing framework Brendan Higgins
2018-11-28 19:36 ` [RFC v3 01/19] kunit: test: add KUnit test runner core Brendan Higgins
2018-11-30  3:14   ` Luis Chamberlain
2018-12-01  1:51     ` Brendan Higgins
2018-12-01  2:57       ` Luis Chamberlain
2018-12-05 13:15     ` Anton Ivanov
2018-12-05 14:45       ` Arnd Bergmann
2018-12-05 14:49         ` Anton Ivanov
2018-11-30  3:28   ` Luis Chamberlain
     [not found]     ` <20181130032802.GG18410-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-01  2:08       ` Brendan Higgins
2018-12-01  3:10         ` Luis Chamberlain
     [not found]           ` <20181201031049.GL28501-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-03 22:47             ` Brendan Higgins
2018-12-01  3:02   ` Luis Chamberlain
2018-11-28 19:36 ` [RFC v3 10/19] kunit: test: add test managed resource tests Brendan Higgins
     [not found] ` <20181128193636.254378-1-brendanhiggins-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2018-11-28 19:36   ` [RFC v3 02/19] kunit: test: add test resource management API Brendan Higgins
2018-11-28 19:36   ` [RFC v3 03/19] kunit: test: add string_stream a std::stream like string builder Brendan Higgins
2018-11-30  3:29     ` Luis Chamberlain
2018-12-01  2:14       ` Brendan Higgins
2018-12-01  3:12         ` Luis Chamberlain
2018-12-03 10:55       ` Petr Mladek [this message]
2018-12-04  0:35         ` Brendan Higgins
2018-11-28 19:36   ` [RFC v3 04/19] kunit: test: add test_stream a std::stream like logger Brendan Higgins
2018-11-28 19:36   ` [RFC v3 05/19] kunit: test: add the concept of expectations Brendan Higgins
2018-11-28 19:36   ` [RFC v3 06/19] arch: um: enable running kunit from User Mode Linux Brendan Higgins
2018-11-28 21:26     ` Rob Herring
2018-11-30  3:37       ` Luis Chamberlain
2018-11-30 14:05         ` Rob Herring
2018-11-30 18:22           ` Luis Chamberlain
     [not found]             ` <20181130182203.GS18410-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-03 23:22               ` Brendan Higgins
2018-11-30  3:30     ` Luis Chamberlain
2018-11-28 19:36   ` [RFC v3 07/19] kunit: test: add initial tests Brendan Higgins
2018-11-30  3:40     ` Luis Chamberlain
2018-12-03 23:26       ` Brendan Higgins
2018-12-03 23:43         ` Luis Chamberlain
2018-11-28 19:36   ` [RFC v3 08/19] arch: um: add shim to trap to allow installing a fault catcher for tests Brendan Higgins
2018-11-30  3:34     ` Luis Chamberlain
     [not found]       ` <20181130033429.GK18410-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-03 23:34         ` Brendan Higgins
     [not found]           ` <CAFd5g45+MAVaSW8HN9x57Y8Um=TV1Oa=-K8yExPBS-4KjLyciQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-12-03 23:46             ` Luis Chamberlain
     [not found]               ` <20181203234628.GR28501-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-04  0:44                 ` Brendan Higgins
2018-11-30  3:41     ` Luis Chamberlain
2018-12-03 23:37       ` Brendan Higgins
2018-11-28 19:36   ` [RFC v3 09/19] kunit: test: add the concept of assertions Brendan Higgins
2018-11-28 19:36   ` [RFC v3 11/19] kunit: add Python libraries for handing KUnit config and kernel Brendan Higgins
2018-11-29 13:54     ` Kieran Bingham
     [not found]       ` <841cf4ae-501b-05ae-5863-a51010709b67-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>
2018-12-03 23:48         ` Brendan Higgins
2018-12-04 20:47           ` Luis Chamberlain
2018-12-06 12:32             ` Kieran Bingham
2018-12-06 15:37               ` Matthew Wilcox
2018-12-07 11:30                 ` Kieran Bingham
2018-12-11 14:09                 ` Petr Mladek
2018-12-11 14:41                   ` Steven Rostedt
2018-12-11 17:01                     ` Anton Ivanov
2019-02-09  0:40                       ` Brendan Higgins
2018-12-07  1:05               ` Luis Chamberlain
2018-12-07 18:35               ` Kent Overstreet
2018-11-30  3:44     ` Luis Chamberlain
2018-12-03 23:50       ` Brendan Higgins
2018-12-04 20:48         ` Luis Chamberlain
2018-11-28 19:36   ` [RFC v3 12/19] kunit: add KUnit wrapper script and simple output parser Brendan Higgins
2018-11-28 19:36   ` [RFC v3 13/19] kunit: improve output from python wrapper Brendan Higgins
2018-11-28 19:36   ` [RFC v3 14/19] Documentation: kunit: add documentation for KUnit Brendan Higgins
2018-11-29 13:56     ` Kieran Bingham
2018-11-30  3:45       ` Luis Chamberlain
     [not found]         ` <20181130034525.GP18410-dAjH6bxAqesAS62YNPtMr3dQhYtBYE6JAL8bYrjMMd8@public.gmane.org>
2018-12-03 23:53           ` Brendan Higgins
2018-12-06 12:16             ` Kieran Bingham
2019-02-09  0:56               ` Brendan Higgins
2019-02-11 12:16                 ` Kieran Bingham
2019-02-12 22:10                   ` Brendan Higgins
2019-02-13 21:55                     ` Kieran Bingham
2019-02-14  0:17                       ` Brendan Higgins
2019-02-14 17:26                         ` Luis Chamberlain
2019-02-14 22:07                           ` Brendan Higgins
2018-11-28 19:36   ` [RFC v3 15/19] MAINTAINERS: add entry for KUnit the unit testing framework Brendan Higgins
2018-11-28 19:36   ` [RFC v3 17/19] of: unittest: migrate tests to run on KUnit Brendan Higgins
2018-11-28 20:56     ` Rob Herring
2018-11-30  0:39       ` Randy Dunlap
     [not found]         ` <18814973-8f0a-4647-a097-fcc3dc0b3cd3-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2018-12-04  0:13           ` Brendan Higgins
2018-12-04 13:40             ` Rob Herring
     [not found]               ` <CAL_JsqL_PivQbrJFEusdKAy-2EQtKL3OHbmyYSK9bzuTOQegqA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-12-05 23:42                 ` Brendan Higgins
2018-12-07  0:41                   ` Rob Herring
2018-12-04  0:08       ` Brendan Higgins
2019-02-13  1:44       ` Brendan Higgins
2019-02-14 20:10         ` Rob Herring
2019-02-14 21:52           ` Brendan Higgins
2019-02-18 22:56         ` Frank Rowand
2019-02-28  0:29           ` Brendan Higgins
2018-12-04 10:56     ` Frank Rowand
2018-11-28 19:36   ` [RFC v3 18/19] of: unittest: split out a couple of test cases from unittest Brendan Higgins
2018-12-04 10:58     ` Frank Rowand
2018-12-05 23:54       ` Brendan Higgins
2019-02-14 23:57         ` Frank Rowand
2019-02-15  0:56           ` Brendan Higgins
2019-02-15  2:05             ` Frank Rowand
2019-02-15 10:56               ` Brendan Higgins
2019-02-18 22:25                 ` Frank Rowand
2019-02-20 20:44                   ` Frank Rowand
2019-02-20 20:47                     ` Frank Rowand
2019-02-28  3:52                     ` Brendan Higgins
2019-03-22  0:22                       ` Frank Rowand
2019-03-22  1:30                         ` Brendan Higgins
2019-03-22  1:47                           ` Frank Rowand
2019-03-25 22:15                             ` Brendan Higgins
2019-09-20 16:57                           ` Rob Herring
2019-09-21 23:57                             ` Frank Rowand
2019-03-22  1:34                         ` Frank Rowand
2019-03-25 22:18                           ` Brendan Higgins
2018-11-28 19:36   ` [RFC v3 19/19] of: unittest: split up some super large test cases Brendan Higgins
2018-11-28 19:36 ` [RFC v3 16/19] arch: um: make UML unflatten device tree when testing Brendan Higgins
2018-11-28 21:16   ` Rob Herring
     [not found]     ` <CAL_JsqK5cG=QzMBFSZ31_-3ujnxqxv=jj3XYajbRLT7yWYZbfw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-12-04  0:00       ` Brendan Higgins
2018-11-30  3:46   ` Luis Chamberlain
2018-12-04  0:02     ` Brendan Higgins
2018-12-04 10:52 ` [RFC v3 00/19] kunit: introduce KUnit, the Linux kernel unit testing framework Frank Rowand
2018-12-04 11:40 ` Frank Rowand
2018-12-04 13:49   ` Rob Herring
2018-12-05 23:10     ` Brendan Higgins
2019-03-22  0:27       ` Frank Rowand
2019-03-25 22:04         ` Brendan Higgins

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=20181203105517.vbedwygttxxbdtan@pathway.suse.cz \
    --to=pmladek@suse.com \
    --cc=Tim.Bird@sony.com \
    --cc=brakmo@fb.com \
    --cc=brendanhiggins@google.com \
    --cc=daniel@ffwll.ch \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=frowand.list@gmail.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jdike@addtoit.com \
    --cc=joe@perches.com \
    --cc=joel@jms.id.au \
    --cc=julia.lawall@lip6.fr \
    --cc=keescook@google.com \
    --cc=khilman@baylibre.com \
    --cc=kieran.bingham@ideasonboard.com \
    --cc=knut.omang@oracle.com \
    --cc=kunit-dev@googlegroups.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=linux-um@lists.infradead.org \
    --cc=mcgrof@kernel.org \
    --cc=mpe@ellerman.id.au \
    --cc=richard@nod.at \
    --cc=robh@kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=shuah@kernel.org \
    /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

Linux-NVDIMM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvdimm/0 linux-nvdimm/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 linux-nvdimm linux-nvdimm/ https://lore.kernel.org/linux-nvdimm \
		linux-nvdimm@lists.01.org
	public-inbox-index linux-nvdimm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.01.lists.linux-nvdimm


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