On Tue, 8 Dec 2020 10:00:24 -0500 Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > On Tue, 8 Dec 2020 21:14:11 +0900 > Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > On Tue, 1 Dec 2020 16:06:56 -0500 > > Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > > From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > > > > > > A bug was reported about the ftrace ring buffer going backwards: > > > > > > Link: https://lore.kernel.org/r/20201124223917.795844-1-elavila@xxxxxxxxxx > > > > > > In debugging this code, I wrote a C program that uses libtracefs to enable > > > all events and function tracing (if it exits), and then read the raw ring > > > buffer binary data and make sure that all the events never go backwards. If > > > they do, then it does a dump of the ring buffer sub buffer page and shows > > > the layout of the events and their deltas. > > > > > > This was a very useful tool, and can be used to make sure that the ring > > > buffer's timestamps are consistently monotonic. > > > > Yeah, this sounds good to me. > > > > > > > > Adding this to the ftrace selftests seems to be a way that this can be > > > tested more often. But this would introduce the first binary code to the > > > ftracetests. > > > > No problem. I think it is better to be placed under ftracetest/bin/ and > > add a PATH before running testcases. > > OK. > > > > > > To make sure that the tests still work on embedded devices (where a > > > compiler may not even exist), and also since this binary incorporates the > > > yet-to-be-released libtracefs library, if the make fails, the test exits > > > with UNTESTED. The UNTESTED is documented as being a place holder which > > > this would be if the make does not work. > > > > Hmm, in some embedded environment, we may not have make nor gcc. > > So it would be better to be build in the kselftest build process as similar > > to the other kselftests. > > > > What about putting the source code under ftracetest/src/. For the embedded > > devices, it can be built with cross-tools (and make it static binary if > > needed) and install it under ftracetest/bin. If we have no cross-build > > tool etc. we just skip building the binary under ftracetest/bin. And if > > the testcase finds there is no binary, it just returns UNRESOLVED or UNTESTED. > > > > OK. I'll look at how to make this for both cases (embedded and not). > Because, my current case is to copy the selftests to the machine and run > them there. So my use case requires the build to happen at test time. But I > can make it where it wont build if the binary already exists. For that case, what about just "make clean" before copy, then the binary will be removed? > > > (currently I returns UNRESOLVED when the test target kmodule is not found) > > I used UNTESTED for a couple of reasons. I figured "UNRESOLVED" was for > lack of kernel features or modules. But this is not a lack of the kernel, > but a lack of user space. If something in user space is lacking (a tool, > library, or binary), then I thought UNTESTED would be a better option. But > if you have a strong opinion on it, I'll change it to UNRESOLVED, otherwise > I'll keep UNTESTED. The idea of UNTESTED/UNRESOLVED (and UNSUPPORTED) came from POSIX standard, it is expained in dejagnu's manual: https://www.gnu.org/software/dejagnu/manual/A-POSIX-Conforming-Test-Framework.html In this case, user can build the user space binary for the environment but does't, so I think UNRESOLVED will fit to that case. So strictly speaking, UNTESTED is just a placeholder which will be implemented in the future. (hmm, it will be a good chance to write a document for it) Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
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