Messages in this thread | | | Subject | Re: [RFC v3 11/19] kunit: add Python libraries for handing KUnit config and kernel | From | Anton Ivanov <> | Date | Tue, 11 Dec 2018 17:01:48 +0000 |
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On 12/11/18 2:41 PM, Steven Rostedt wrote: > On Tue, 11 Dec 2018 15:09:26 +0100 > Petr Mladek <pmladek@suse.com> wrote: > >>> We have liburcu already, which is good. The main sticking points are: >>> >>> - printk has started adding a lot of %pX enhancements which printf >>> obviously doesn't know about. >> I wonder how big problem it is and if it is worth using another >> approach. > No, please do not change the %pX approach. > >> An alternative would be to replace them with helper functions >> the would produce the same string. The meaning would be easier >> to understand. But concatenating with the surrounding text >> would be less elegant. People might start using pr_cont() >> that is problematic (mixed lines). >> >> Also the %pX formats are mostly used to print context of some >> structures. Even the helper functions would need some maintenance >> to keep them compatible. >> >> BTW: The printk() feature has been introduced 10 years ago by >> the commit 4d8a743cdd2690c0bc8 ("vsprintf: add infrastructure >> support for extended '%p' specifiers"). > trace-cmd and perf know about most of the %pX data and how to read it. > Perhaps we can extend the libtraceevent library to export a generic way > to read data from printk() output for other tools to use.
Going back for a second to using UML for this. UML console at present is interrupt driven - it emulates serial IO using several different back-ends (file descriptors, xterm or actual tty/ptys). Epoll events on the host side are used to trigger the UML interrupts - both read and write.
This works OK for normal use, but may result in all kinds of interesting false positives/false negatives when UML is used to run unit tests against a change which changes interrupt behavior.
IMO it may be useful to consider some alternatives specifically for unit test coverage purposes where printk and/or the whole console output altogether bypass some of the IRQ driven semantics.
--
Anton R. Ivanov
Cambridge Greys Limited, England and Wales company No 10273661 http://www.cambridgegreys.com/
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