Re: [PATCH] tr2: log parent process name

> 
> 
> 
> On 5/6/21 8:29 PM, Emily Shaffer wrote:
> > It can be useful to tell who invoked Git - was it invoked manually by a
> > user via CLI or script? By an IDE? Knowing where the Git invocation came
> > from can help with debugging to isolate where the problem came from.
> > 
> > Unfortunately, there's no cross-platform reliable way to gather the name
> > of the parent process. If procfs is present, we can use that; otherwise
> > we will need to discover the name another way. However, the process ID
> > should be sufficient regardless of platform.
> > 
> > Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
> > ---
> > We briefly discussed hiding this behind a config, internally. However, I
> > wanted to include the parent name alongside the cmd_start event, which
> > happens very early (maybe before config gathering?).
> > 
> > Maybe it's better to log the parent_name as its own event, since it
> > shouldn't change over the lifetime of the process?
> > 
> > procfs is very non-portable, though - I think this won't even work on
> > MacOS. So I'm curious if anybody has better suggestions for how to do
> > this.
> > 
> >   - Emily
> 
> 
> Look at `trace2_collect_process_info()` in `trace2.h` and
> `compat/win32/trace2_win32_process_info.c`.
> 
> That function is designed to let the process call out to
> platform-specific code to do things like getting the name
> of the invoking process.
> 
> It is called with an enum to indicate when/why it is being
> called.
> 
> On Windows, I have platform code to get the process ancestry,
> the peak VM usage, and whether the process is being debugged.
> Two of those were easy....  And all are very platform-specific.
> 
> They all generate events of the form:
> 
> 	trace2_data_*("process", "windows/<something>", ...)
> 
> Some of my `t021[012]/` helper scripts exclude "process" category
> messages from the output to make the t*.sh tests portable.
> 
> 
> To implement a /proc lookup as you have suggested, I would
> fixup the Makefile or config.mak.uname to include something
> like a "HAVE_..." feature and then use that at the
> bottom of trace2.h to declare a trace2_collect_process_info()
> function and then have your code in compat/procinfo.c hide
> behind my interface.
> 
> Your code should emits events of the form:
> 
> 	trace2_data_*("process", "linux/<something>", ...)
> 
> I notice there are several `PROCFS_*` symbols currently defined
> in `config.mak.uname` so maybe this should be:
> 
> 	trace2_data_*("process", "procfs/<something>", ...)
> 
> (I'm not sure how similar code for Linux and the various BSD
> versions would be.)