Re: [PATCH v1 1/2] perf sched: Avoid segv if tp_handler not set

[Arnaldo Carvalho de Melo]

On Tue, May 05, 2026 at 02:56:02PM -0700, Ian Rogers wrote:
> On Mon, Apr 6, 2026 at 10:53 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > On Fri, Apr 03, 2026 at 08:29:25AM -0700, Ian Rogers wrote:
> > > On Thu, Apr 2, 2026 at 7:42 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > > > On Tue, Mar 31, 2026 at 10:59:52PM -0700, Ian Rogers wrote:
> > > > > On Thu, Mar 26, 2026 at 4:20 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > > > > > On Fri, Mar 20, 2026 at 11:14:47PM -0700, Ian Rogers wrote:
> > > > > > > Doing a `perf sched record` then `perf sched stats report` crashes as
> > > > > > > the tp_handler isn't set. Add extra checks that tp_handler is set
> > > > > > > before accessing through it.

> > > > > > Oh.. unintended use case. :)  Probably better to add a dummy handler
> > > > > > for `perf sched stats report`.

> > > > > Perhaps. I'd prefer to land the simpler change as-is.

> > > > Well.. I guess the dummy handler approach would be simpler and perform
> > > > better. :)

> > > > +++ b/tools/perf/builtin-sched.c
> > > > @@ -4955,6 +4955,7 @@ int cmd_sched(int argc, const char **argv)
> > > >                 .switch_event       = replay_switch_event,
> > > >                 .fork_event         = replay_fork_event,
> > > >         };
> > > > +       struct trace_sched_handler stats_ops  = {};
> > >
> > > Oh, because there's an existing null test on the function pointer we
> > > don't need dummy functions, which is what I thought you were asking
> > > for. I'm still not convinced this is very intention revealing, but if
> > > it works for you then you can have my reviewed-by tag.

> > Applied this and the patch 2 to perf-tools-next, thanks!
 
> Thanks Namhyung. Did this get accidentally dropped? I'm not seeing it
> in perf-tools-next.

Not applying:

⬢ [acme@toolbx perf-tools-next2]$ b4 am -ctsl --cc-trailers CAP-5=fW-H-ri3MdVv4Vh4xiyB-qpDqnO3gqXR+XyfMK+kXpHQA@xxxxxxxxxxxxxx
Grabbing thread from lore.kernel.org/all/CAP-5%3DfW-H-ri3MdVv4Vh4xiyB-qpDqnO3gqXR%2BXyfMK%2BkXpHQA@xxxxxxxxxxxxxx/t.mbox.gz
Checking for newer revisions
Grabbing search results from lore.kernel.org
Analyzing 10 messages in the thread
Analyzing 0 code-review messages
Checking attestation on all messages, may take a moment...
---
  ✗ [PATCH v1 1/2] perf sched: Avoid segv if tp_handler not set
    + Tested-by: Swapnil Sapkal <swapnil.sapkal@xxxxxxx> (✓ DKIM/amd.com)
    + Link: https://lore.kernel.org/r/20260321061448.810525-1-irogers@xxxxxxxxxx
    + Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
  ✗ [PATCH v1 2/2] perf tests sched stats: Write output to temp file
    + Tested-by: Swapnil Sapkal <swapnil.sapkal@xxxxxxx> (✓ DKIM/amd.com)
    + Link: https://lore.kernel.org/r/20260321061448.810525-2-irogers@xxxxxxxxxx
    + Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
  ---
  ✗ BADSIG: DKIM/google.com
---
Total patches: 2
---
 Link: https://lore.kernel.org/r/20260321061448.810525-1-irogers@xxxxxxxxxx
 Base: not specified
       git am ./20260320_irogers_perf_sched_avoid_segv_if_tp_handler_not_set.mbx
⬢ [acme@toolbx perf-tools-next]$        git am ./20260320_irogers_perf_sched_avoid_segv_if_tp_handler_not_set.mbx
Applying: perf sched: Avoid segv if tp_handler not set
Applying: perf tests sched stats: Write output to temp file
error: patch failed: tools/perf/tests/shell/perf_sched_stats.sh:4
error: tools/perf/tests/shell/perf_sched_stats.sh: patch does not apply
Patch failed at 0002 perf tests sched stats: Write output to temp file
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
⬢ [acme@toolbx perf-tools-next2]$ git log --oneline -5
5a5b82a2a9bf1d3f (HEAD -> perf-tools-next) perf sched: Avoid segv if tp_handler not set
2d840126356314bf perf sched stats: Fix segmentation faults, memory leaks, and stale pointers in diff mode
8c8f2093614373ea perf build: Remove NO_GTK2 build test
53bc032892782e54 perf build: Add -fms-extensions for GEN_VMLINUX_H=1
e41cac8617a9b399 perf build: Update error message for BUILD_NONDISTRO=1
⬢ [acme@toolbx perf-tools-next]$