Messages in this thread | | | Date | Fri, 28 Oct 2022 12:59:54 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH] selftests/ftrace: Limit number of lines processed in 'trace' |
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Masami Hiramatsu wrote: > On Wed, 19 Oct 2022 15:15:09 +0530 > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: > >> Steven Rostedt wrote: >> > On Wed, 19 Oct 2022 00:19:49 +0900 >> > Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: >> > >> >> > You need to make sure that the "pause-on-trace" option is set or tracing_on >> >> > is set to 0 (disabled). Otherwise, if the tracing is still active, then the >> >> > reading of the trace file could potentially never end. >> >> >> >> initialize_ftrace() does this setting. So it must be set. >> >> If you run the ftracetest on old kernel, this feature is not there and >> >> it may cause a trouble. Naveen, can you clarify it? >> >> Yes, the change to not pause on opening the trace file looks to be the >> problem. >> >> > >> > But for old kernels that do not have "pause-on-trace" it should be the >> > default. The "pause-on-trace" was added when the default was changed to not >> > pause the trace while reading it. >> >> It looks like the kernel patch was picked up, but Masami's patch for the >> selftest wasn't backported. I have requested a test with that applied. > > Good! That should be backported too. > BTW, which kernel version do you test?
This was reported in internal tests with RHEL kernel.
> >> >> Separately, before I saw your response, I came up with the below patch >> to update the selftests to disable tracing before reading the trace >> file. I have also requested this to be tested. > > Yeah, OK. This also looks OK to me.
This patch doesn't seem to be enough - event/subsystem-enable.tc also needs updates. In light of that, I'm not sure if the large number of disable_tracing statements required makes sense. So, I'm inclined to drop this patch in favour of the existing pause-on-trace option.
Thanks, Naveen
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