From: pmladek at suse.com (Petr Mladek) Subject: [RFC v3 03/19] kunit: test: add string_stream a std::stream like string builder Date: Mon, 3 Dec 2018 11:55:17 +0100 [thread overview] 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
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From: pmladek@suse.com (Petr Mladek) Subject: [RFC v3 03/19] kunit: test: add string_stream a std::stream like string builder Date: Mon, 3 Dec 2018 11:55:17 +0100 [thread overview] Message-ID: <20181203105517.vbedwygttxxbdtan@pathway.suse.cz> (raw) Message-ID: <20181203105517.i9mPEoVMHz8l-FpeZ6tRpJT03iLIgCdWBBKNk5m1rxQ@z> (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@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
next prev parent reply other threads:[~2018-12-03 10:55 UTC|newest] Thread overview: 232+ 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 01/19] kunit: test: add KUnit test runner core brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-30 3:14 ` mcgrof 2018-11-30 3:14 ` Luis Chamberlain 2018-12-01 1:51 ` brendanhiggins 2018-12-01 1:51 ` Brendan Higgins 2018-12-01 2:57 ` mcgrof 2018-12-01 2:57 ` Luis Chamberlain 2018-12-05 13:15 ` anton.ivanov 2018-12-05 13:15 ` Anton Ivanov 2018-12-05 14:45 ` arnd 2018-12-05 14:45 ` Arnd Bergmann 2018-12-05 14:49 ` anton.ivanov 2018-12-05 14:49 ` Anton Ivanov 2018-11-30 3:28 ` mcgrof 2018-11-30 3:28 ` Luis Chamberlain 2018-12-01 2:08 ` brendanhiggins 2018-12-01 2:08 ` Brendan Higgins 2018-12-01 3:10 ` mcgrof 2018-12-01 3:10 ` Luis Chamberlain 2018-12-03 22:47 ` brendanhiggins 2018-12-03 22:47 ` Brendan Higgins 2018-12-01 3:02 ` mcgrof 2018-12-01 3:02 ` Luis Chamberlain 2018-11-28 19:36 ` [RFC v3 02/19] kunit: test: add test resource management API brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 03/19] kunit: test: add string_stream a std::stream like string builder brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-30 3:29 ` mcgrof 2018-11-30 3:29 ` Luis Chamberlain 2018-12-01 2:14 ` brendanhiggins 2018-12-01 2:14 ` Brendan Higgins 2018-12-01 3:12 ` mcgrof 2018-12-01 3:12 ` Luis Chamberlain 2018-12-03 10:55 ` pmladek [this message] 2018-12-03 10:55 ` Petr Mladek 2018-12-04 0:35 ` brendanhiggins 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 05/19] kunit: test: add the concept of expectations brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 06/19] arch: um: enable running kunit from User Mode Linux brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 21:26 ` robh 2018-11-28 21:26 ` Rob Herring 2018-11-30 3:37 ` mcgrof 2018-11-30 3:37 ` Luis Chamberlain 2018-11-30 14:05 ` robh 2018-11-30 14:05 ` Rob Herring 2018-11-30 18:22 ` mcgrof 2018-11-30 18:22 ` Luis Chamberlain 2018-12-03 23:22 ` brendanhiggins 2018-12-03 23:22 ` Brendan Higgins 2018-11-30 3:30 ` mcgrof 2018-11-30 3:30 ` Luis Chamberlain 2018-11-28 19:36 ` [RFC v3 07/19] kunit: test: add initial tests brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-30 3:40 ` mcgrof 2018-11-30 3:40 ` Luis Chamberlain 2018-12-03 23:26 ` brendanhiggins 2018-12-03 23:26 ` Brendan Higgins 2018-12-03 23:43 ` mcgrof 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-30 3:34 ` mcgrof 2018-11-30 3:34 ` Luis Chamberlain 2018-12-03 23:34 ` brendanhiggins 2018-12-03 23:34 ` Brendan Higgins 2018-12-03 23:46 ` mcgrof 2018-12-03 23:46 ` Luis Chamberlain 2018-12-04 0:44 ` brendanhiggins 2018-12-04 0:44 ` Brendan Higgins 2018-11-30 3:41 ` mcgrof 2018-11-30 3:41 ` Luis Chamberlain 2018-12-03 23:37 ` brendanhiggins 2018-12-03 23:37 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 09/19] kunit: test: add the concept of assertions brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 10/19] kunit: test: add test managed resource tests brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 11/19] kunit: add Python libraries for handing KUnit config and kernel brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-29 13:54 ` kieran.bingham 2018-11-29 13:54 ` Kieran Bingham 2018-12-03 23:48 ` brendanhiggins 2018-12-03 23:48 ` Brendan Higgins 2018-12-04 20:47 ` mcgrof 2018-12-04 20:47 ` Luis Chamberlain 2018-12-06 12:32 ` kieran.bingham 2018-12-06 12:32 ` Kieran Bingham 2018-12-06 15:37 ` willy 2018-12-06 15:37 ` Matthew Wilcox 2018-12-07 11:30 ` kieran.bingham 2018-12-07 11:30 ` Kieran Bingham 2018-12-11 14:09 ` pmladek 2018-12-11 14:09 ` Petr Mladek 2018-12-11 14:41 ` rostedt 2018-12-11 14:41 ` Steven Rostedt 2018-12-11 17:01 ` anton.ivanov 2018-12-11 17:01 ` Anton Ivanov 2019-02-09 0:40 ` brendanhiggins 2019-02-09 0:40 ` Brendan Higgins 2018-12-07 1:05 ` mcgrof 2018-12-07 1:05 ` Luis Chamberlain 2018-12-07 18:35 ` kent.overstreet 2018-12-07 18:35 ` Kent Overstreet 2018-11-30 3:44 ` mcgrof 2018-11-30 3:44 ` Luis Chamberlain 2018-12-03 23:50 ` brendanhiggins 2018-12-03 23:50 ` Brendan Higgins 2018-12-04 20:48 ` mcgrof 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 13/19] kunit: improve output from python wrapper brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 14/19] Documentation: kunit: add documentation for KUnit brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-29 13:56 ` kieran.bingham 2018-11-29 13:56 ` Kieran Bingham 2018-11-30 3:45 ` mcgrof 2018-11-30 3:45 ` Luis Chamberlain 2018-12-03 23:53 ` brendanhiggins 2018-12-03 23:53 ` Brendan Higgins 2018-12-06 12:16 ` kieran.bingham 2018-12-06 12:16 ` Kieran Bingham 2019-02-09 0:56 ` brendanhiggins 2019-02-09 0:56 ` Brendan Higgins 2019-02-11 12:16 ` kieran.bingham 2019-02-11 12:16 ` Kieran Bingham 2019-02-12 22:10 ` brendanhiggins 2019-02-12 22:10 ` Brendan Higgins 2019-02-13 21:55 ` kieran.bingham 2019-02-13 21:55 ` Kieran Bingham 2019-02-14 0:17 ` brendanhiggins 2019-02-14 0:17 ` Brendan Higgins 2019-02-14 17:26 ` mcgrof 2019-02-14 17:26 ` Luis Chamberlain 2019-02-14 22:07 ` brendanhiggins 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 16/19] arch: um: make UML unflatten device tree when testing brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-11-28 21:16 ` robh 2018-11-28 21:16 ` Rob Herring 2018-12-04 0:00 ` brendanhiggins 2018-12-04 0:00 ` Brendan Higgins 2018-11-30 3:46 ` mcgrof 2018-11-30 3:46 ` Luis Chamberlain 2018-12-04 0:02 ` brendanhiggins 2018-12-04 0:02 ` Brendan Higgins 2018-11-28 19:36 ` [RFC v3 17/19] of: unittest: migrate tests to run on KUnit brendanhiggins 2018-11-28 19:36 ` Brendan Higgins [not found] ` <CAL_Jsq+09Kx7yMBC_Jw45QGmk6U_fp4N6HOZDwYrM4tWw+_dOA@mail.gmail.com> 2018-11-30 0:39 ` rdunlap 2018-11-30 0:39 ` Randy Dunlap 2018-12-04 0:13 ` brendanhiggins 2018-12-04 0:13 ` Brendan Higgins 2018-12-04 13:40 ` robh 2018-12-04 13:40 ` Rob Herring 2018-12-05 23:42 ` brendanhiggins 2018-12-05 23:42 ` Brendan Higgins 2018-12-07 0:41 ` robh 2018-12-07 0:41 ` Rob Herring 2018-12-04 0:08 ` brendanhiggins 2018-12-04 0:08 ` Brendan Higgins 2019-02-13 1:44 ` brendanhiggins 2019-02-13 1:44 ` Brendan Higgins 2019-02-14 20:10 ` robh 2019-02-14 20:10 ` Rob Herring 2019-02-14 21:52 ` brendanhiggins 2019-02-14 21:52 ` Brendan Higgins 2019-02-18 22:56 ` frowand.list 2019-02-18 22:56 ` Frank Rowand 2019-02-28 0:29 ` brendanhiggins 2019-02-28 0:29 ` Brendan Higgins 2018-12-04 10:56 ` frowand.list 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-12-04 10:58 ` frowand.list 2018-12-04 10:58 ` Frank Rowand 2018-12-05 23:54 ` brendanhiggins 2018-12-05 23:54 ` Brendan Higgins 2019-02-14 23:57 ` frowand.list 2019-02-14 23:57 ` Frank Rowand 2019-02-15 0:56 ` brendanhiggins 2019-02-15 0:56 ` Brendan Higgins 2019-02-15 2:05 ` frowand.list 2019-02-15 2:05 ` Frank Rowand 2019-02-15 10:56 ` brendanhiggins 2019-02-15 10:56 ` Brendan Higgins 2019-02-18 22:25 ` frowand.list 2019-02-18 22:25 ` Frank Rowand 2019-02-20 20:44 ` frowand.list 2019-02-20 20:44 ` Frank Rowand 2019-02-20 20:47 ` frowand.list 2019-02-20 20:47 ` Frank Rowand 2019-02-28 3:52 ` brendanhiggins 2019-02-28 3:52 ` Brendan Higgins 2019-03-22 0:22 ` frowand.list 2019-03-22 0:22 ` Frank Rowand 2019-03-22 1:30 ` brendanhiggins 2019-03-22 1:30 ` Brendan Higgins 2019-03-22 1:47 ` frowand.list 2019-03-22 1:47 ` Frank Rowand 2019-03-25 22:15 ` brendanhiggins 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 ` frowand.list 2019-03-22 1:34 ` Frank Rowand 2019-03-25 22:18 ` brendanhiggins 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 brendanhiggins 2018-11-28 19:36 ` Brendan Higgins 2018-12-04 10:52 ` [RFC v3 00/19] kunit: introduce KUnit, the Linux kernel unit testing framework frowand.list 2018-12-04 10:52 ` Frank Rowand 2018-12-04 11:40 ` frowand.list 2018-12-04 11:40 ` Frank Rowand 2018-12-04 13:49 ` robh 2018-12-04 13:49 ` Rob Herring 2018-12-05 23:10 ` brendanhiggins 2018-12-05 23:10 ` Brendan Higgins 2019-03-22 0:27 ` frowand.list 2019-03-22 0:27 ` Frank Rowand 2019-03-25 22:04 ` brendanhiggins 2019-03-25 22:04 ` Brendan Higgins
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