Re: perf: Live mode flamegraph recording results in segmentation fault

[Namhyung Kim <namhyung@kernel.org>]

On Mon, Mar 10, 2025 at 11:53:06AM +0000, James Clark wrote:
> 
> 
> On 07/03/2025 4:25 pm, David wrote:
> > I've reproduced this on recent versions of Debian, Ubuntu, CentOS, and
> > Fedora,
> > and I used to be able to downgrade perf and it would work, but an early
> > enough
> > version of perf is no longer available from most package repositories.
> > 
> > Steps I have taken to reproduce:
> > 
> > 1. Install perf from a distro package manager. ( `sudo dnf install perf`)
> > 
> > ```
> >   $ perf --version
> > 
> > perf version 6.13.5-200.fc41.x86_64)
> > ```
> > 
> > 2. Attempt a live flamegraph report:
> > 
> > ```
> > 
> > $ perf script flamegraph ls
> > /usr/libexec/perf-core/scripts/python/bin/flamegraph-report: line 3:
> > 1644 Segmentation fault      (core dumped) perf script -s
> > "$PERF_EXEC_PATH"/scripts/python/flamegraph.py -- "$@"
> > ```
> > 
> > 
> 
> Hi David,
> 
> Are you able to bisect this to find the breaking commit?
> 
> Is this the full output you get? I'm not able to reproduce your exact issue.
> I do see a bug with the template download prompt but it produces more output
> than you have:
> 
>  $ perf script flamegraph ls
> 
>   Warning: Flame Graph template '/usr/share/d3-flame-graph/d3-
>   flamegraph-base.html' does not exist.
>   [...]
>   s = input("Do you wish to download a template from cdn.jsdelivr.net?
>   (this warning can be suppressed with --allow-download) [yn] ").lower()
>   OSError: [Errno 9] Bad file descriptor
>   Fatal Python error: handler_call_die: problem in Python trace event
>   handler
>   Python runtime state: initialized
> 
>   Current thread 0x00007d1916afd400 (most recent call first):
>   <no Python frame>
> 
>   Extension modules: apt_pkg (total: 1)
>   Aborted (core dumped)
> 
> But if I avoid the record/report wrapper and go straight to the script it
> works:
> 
>   $ perf record -g ls
>   $ perf script flamegraph.py
> 
>   [...]
>   Do you wish to download a template from cdn.jsdelivr.net? (this
>   warning can be suppressed with --allow-download) [yn] y
> 
>   dumping data to flamegraph.html
> 
> I'm wondering if the template prompt ever worked in conjunction with the
> wrappers? Maybe they were only tested with the template already installed,
> or the script was always used directly when the need for a template was
> added.

I don't know but it didn't work well for me too.  Maybe it should have
default 'y' for live mode.

Thanks,
Namhyung