Re: [PATCH v4 8/8] selftests/verification: add tlob selftests

[Gabriele Monaco <gmonaco@redhat.com>]

On Wed, 2026-07-08 at 23:38 +0800, wen.yang@linux.dev wrote:
> From: Wen Yang <wen.yang@linux.dev>
> 
> Add seven ftrace-style test scripts for the tlob RV monitor under
> tools/testing/selftests/verification/test.d/tlob/.  The tests cover
> uprobe binding management, budget violation detection, and per-state
> time accounting.
> 
> Helper binaries tlob_target and tlob_sym are included in the same
> directory so the suite is self-contained.  tlob_sym resolves ELF
> symbol offsets for uprobe registration; tlob_target provides busy-spin,
> sleep, and preempt workloads.
> 
> ftracetest is updated to walk up the directory tree when searching for
> test.d/functions, so monitor subdirectories can be passed as the test
> directory without placing a dummy functions shim in each new directory.
> 
> Signed-off-by: Wen Yang <wen.yang@linux.dev>
> ---

...

> +"$UPROBE_TARGET" 30000 &       # busy mode: tlob_busy_work fires every 200 ms
> +busy_pid=$!
> +"$UPROBE_TARGET" 30000 sleep & # sleep mode: tlob_sleep_work fires every 200
> ms
> +sleep_pid=$!
> +sleep 0.05
> +
> +echo 1 > /sys/kernel/tracing/events/rv/error_env_tlob/enable
> +echo 1 > /sys/kernel/tracing/events/rv/detail_env_tlob/enable
> +echo 1 > /sys/kernel/tracing/tracing_on
> +echo 1 > monitors/tlob/enable
> +echo > /sys/kernel/tracing/trace
> +
> +# Binding A: 5 s budget on the busy probe - must not fire in 200 ms loops.
> +echo "p ${UPROBE_TARGET}:${busy_offset} ${busy_stop} threshold=5000000000" >
> "$TLOB_MONITOR"
> +# Binding B: 10 us budget on the sleep probe - fires on first invocation.
> +echo "p ${UPROBE_TARGET}:${sleep_offset} ${sleep_stop} threshold=10000" >
> "$TLOB_MONITOR"
> +
> +# Wait up to 2 s for error_env_tlob from binding B.
> +found=0; i=0
> +while [ "$i" -lt 20 ]; do
> +	sleep 0.1
> +	grep -q "error_env_tlob" /sys/kernel/tracing/trace && { found=1;
> break; }
> +	i=$((i+1))
> +done

Be careful when starting tasks and making assertions (e.g. grep) before
killing them, in case those assertions fail, set -e would exit
immediately and we'll skip stopping the tasks.

I'd say whenever you start tlob_target (or anything else) you can do:

  teardown() {
  	kill "$sleep_pid" 2>/dev/null || true; wait "$sleep_pid" 2>/dev/null || true
  	kill "$busy_pid" 2>/dev/null || true; wait "$busy_pid" 2>/dev/null || true
  }
  trap teardown EXIT

just to be safe. This will kill and wait again if you need teardown
before the end of the test, but that isn't an issue.

> +
> +echo "-${UPROBE_TARGET}:${busy_offset}" > "$TLOB_MONITOR" 2>/dev/null
> +echo "-${UPROBE_TARGET}:${sleep_offset}" > "$TLOB_MONITOR" 2>/dev/null
> +kill "$sleep_pid" 2>/dev/null || true; wait "$sleep_pid" 2>/dev/null || true
> +kill "$busy_pid" 2>/dev/null || true; wait "$busy_pid" 2>/dev/null || true
> +
> +echo 0 > monitors/tlob/enable
> +echo 0 > /sys/kernel/tracing/events/rv/error_env_tlob/enable
> +echo 0 > /sys/kernel/tracing/events/rv/detail_env_tlob/enable
> +
> +[ "$found" = "1" ]
> +# error_env_tlob payload: clock variable must be present.
> +# The event field can be "budget_exceeded" (hrtimer path) or the DA event
> +# name ("sleep", "preempt") depending on which fires first; don't constrain
> it.
> +grep "error_env_tlob" /sys/kernel/tracing/trace | head -n 1 | grep -q
> "clk_elapsed="
> +# detail_env_tlob must appear alongside the error.
> +grep -q "detail_env_tlob" /sys/kernel/tracing/trace
> +
> +echo > /sys/kernel/tracing/trace
> diff --git
> a/tools/testing/selftests/verification/test.d/tlob/uprobe_no_event.tc
> b/tools/testing/selftests/verification/test.d/tlob/uprobe_no_event.tc
> new file mode 100644
> index 000000000000..bb2eeef17019
> --- /dev/null
> +++ b/tools/testing/selftests/verification/test.d/tlob/uprobe_no_event.tc
> @@ -0,0 +1,19 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# description: Test tlob monitor no spurious events without active uprobe
> binding
> +# requires: tlob:monitor
> +
> +TLOB_MONITOR=monitors/tlob/monitor

This appears unused here.

Thanks,
Gabriele