[CWS] Do not use fentry if tasks_rcu_exit_srcu kernel symbol is found

[YoannGh]

What does this PR do?

Revert back to kprobe mode when tasks_rcu_exit_srcu lock is found in kernel symbols.
This lock might cause a deadlock when system-probe exists, and was removed upstream by the following commit (torvalds/linux@1612160).

Credits to @usamasaqib for the investigation.

Motivation

Describe how you validated your changes

Tested with fentry enabled (DD_EVENT_MONITORING_CONFIG_EVENT_STREAM_USE_FENTRY=true) on:

• Ubuntu kernel 6.8.0-53-generic: made sure fentry wasn't used and the kprobe fallback was used instead
• Ubuntu kernel 6.11.0-14-generic: made sure fentry was used

Possible Drawbacks / Trade-offs

Additional Notes

[usamasaqib]

Could you move this check into a separate function somewhere in pkg/ebpf? I am sure other teams will also want to use this.
Maybe we can have pkg/ebpf/kernel_bugs.go for similar detections, if you thinks it appropriate.

[agent-platform-auto-pr]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv aws.create-vm --pipeline-id=55398765 --os-family=ubuntu

Note: This applies to commit 1ecadc8

[agent-platform-auto-pr]

Uncompressed package size comparison

Comparison with ancestor ab77e3ac7e293e6992e9ba3dc9b79a794bfd783b

Diff per package

package	diff	status	size	ancestor	threshold
datadog-agent-amd64-deb	0.00MB	✅	868.95MB	868.95MB	0.50MB
datadog-agent-arm64-deb	0.00MB	✅	857.38MB	857.38MB	0.50MB
datadog-dogstatsd-amd64-deb	0.00MB	✅	59.11MB	59.11MB	0.50MB
datadog-dogstatsd-x86_64-rpm	0.00MB	✅	59.19MB	59.19MB	0.50MB
datadog-dogstatsd-x86_64-suse	0.00MB	✅	59.19MB	59.19MB	0.50MB
datadog-dogstatsd-arm64-deb	0.00MB	✅	56.58MB	56.58MB	0.50MB
datadog-heroku-agent-amd64-deb	0.00MB	✅	441.15MB	441.15MB	0.50MB
datadog-iot-agent-amd64-deb	0.00MB	✅	86.39MB	86.39MB	0.50MB
datadog-iot-agent-x86_64-rpm	0.00MB	✅	86.46MB	86.46MB	0.50MB
datadog-iot-agent-x86_64-suse	0.00MB	✅	86.46MB	86.46MB	0.50MB
datadog-iot-agent-arm64-deb	0.00MB	✅	82.66MB	82.66MB	0.50MB
datadog-iot-agent-aarch64-rpm	0.00MB	✅	82.73MB	82.73MB	0.50MB
datadog-agent-aarch64-rpm	-0.00MB	✅	867.13MB	867.13MB	0.50MB
datadog-agent-x86_64-rpm	-0.00MB	✅	878.72MB	878.72MB	0.50MB
datadog-agent-x86_64-suse	-0.00MB	✅	878.72MB	878.72MB	0.50MB

Decision

✅ Passed

[agent-platform-auto-pr]

Static quality checks ✅

Please find below the results from static quality gates

Info

Result	Quality gate	On disk size	On disk size limit	On wire size	On wire size limit
✅	static_quality_gate_agent_deb_amd64	840.56MiB	858.45MiB	203.55MiB	214.3MiB
✅	static_quality_gate_docker_agent_amd64	924.85MiB	942.69MiB	309.87MiB	321.56MiB
✅	static_quality_gate_docker_agent_arm64	937.14MiB	952.69MiB	293.76MiB	351.22MiB
✅	static_quality_gate_docker_agent_jmx_amd64	1.1GiB	1.11GiB	384.94MiB	395.8MiB
✅	static_quality_gate_docker_agent_jmx_arm64	1.1GiB	1.11GiB	364.84MiB	375.5MiB
✅	static_quality_gate_docker_dogstatsd_amd64	47.9MiB	57.88MiB	18.3MiB	28.29MiB
✅	static_quality_gate_docker_dogstatsd_arm64	46.29MiB	56.27MiB	17.07MiB	27.06MiB
✅	static_quality_gate_docker_cluster_agent_amd64	267.76MiB	277.7MiB	107.32MiB	117.28MiB
✅	static_quality_gate_docker_cluster_agent_arm64	283.79MiB	293.73MiB	102.14MiB	112.12MiB

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 0c6408ad-80c8-4a7d-bb0d-baca4c558501

Baseline: ab77e3a
Comparison: 1ecadc8
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_logs	% cpu utilization	+4.47	[+1.36, +7.59]	1	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+2.25	[+1.36, +3.15]	1	Logs
➖	file_tree	memory utilization	+1.01	[+0.94, +1.08]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	+0.06	[-0.01, +0.13]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.05	[-0.67, +0.76]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	+0.02	[-0.88, +0.92]	1	Logs
➖	file_to_blackhole_0ms_latency_http2	egress throughput	+0.01	[-0.86, +0.89]	1	Logs
➖	quality_gate_idle	memory utilization	+0.01	[-0.02, +0.05]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.28, +0.30]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.02, +0.03]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	-0.01	[-0.65, +0.62]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.01	[-0.85, +0.83]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.06	[-0.83, +0.72]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.08	[-0.87, +0.70]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.20	[-0.66, +0.25]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.67	[-0.73, -0.61]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http1	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http1	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http2	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http2	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency_linear_load	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_300ms_latency	lost_bytes	10/10
✅	file_to_blackhole_300ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10
✅	quality_gate_logs	lost_bytes	10/10
✅	quality_gate_logs	memory_usage	10/10

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.

[YoannGh]

/merge

[dd-devflow]

Devflow running: /merge

View all feedbacks in Devflow UI.

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2025-02-10 17:06:19 UTC ℹ️ MergeQueue: merge request added to the queue

The median merge time in main is 30m.

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2025-02-10 17:41:59 UTC ℹ️ MergeQueue: This merge request was merged