fix(system-probe): protect module loader registry with mutex during Register by pgimalac · Pull Request #54950 · DataDog/datadog-agent

pgimalac · 2026-08-17T09:06:33Z

What does this PR do?

Fixes a data race on the module loader registry: Register wrote l.cfg, l.stats, and iterated l.modules without holding the loader mutex, racing with GetStats which takes the lock. Added l.Lock() around the writes and snapshotted module entries before spawning stats goroutines.

Motivation

Fix a race, found via a race-detector-enabled build in staging (see #54333 for context).

Describe how you validated your changes

No unit test added — Register requires full eBPF factories, config, and dependencies that can't be constructed in a unit test, and duplicating the internal logic in a test wouldn't validate the actual fix. The race is eliminated by construction: all writes to the shared fields now go through the same mutex that GetStats already takes.

github-actions · 2026-08-17T09:06:43Z

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datadog-datadog-prod-us1 · 2026-08-17T09:22:59Z

🎯 Code Coverage (details)
• Patch Coverage: 0.00%
• Overall Coverage: 52.43% (+0.05%)

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🔗 Commit SHA: 27bef0b | Docs | Datadog PR Page | Give us feedback!}

dd-octo-sts · 2026-08-17T09:33:13Z

Files inventory check summary

File checks results against ancestor 92f6b05c:

Results for datadog-agent_7.84.0~devel.git.224.27bef0b.pipeline.131302790-1_amd64.deb:

No change detected

Results for datadog-iot-agent_7.84.0~devel.git.224.27bef0b.pipeline.131302790-1_amd64.deb:

No change detected

dd-octo-sts · 2026-08-17T09:42:01Z

Static quality checks

✅ Please find below the results from static quality gates
Comparison made with ancestor 92f6b05
📊 Static Quality Gates Dashboard
🔗 SQG Job

33 successful checks with minimal change (< 2 KiB)

	Quality gate	Current Size
✅	agent_deb_amd64	760.218 MiB
✅	agent_deb_amd64_fips	713.079 MiB
✅	agent_heroku_amd64	312.557 MiB
✅	agent_msi	644.203 MiB
✅	agent_rpm_amd64	760.201 MiB
✅	agent_rpm_amd64_fips	713.062 MiB
✅	agent_rpm_arm64	735.966 MiB
✅	agent_rpm_arm64_fips	692.153 MiB
✅	agent_suse_amd64	760.201 MiB
✅	agent_suse_amd64_fips	713.062 MiB
✅	agent_suse_arm64	735.966 MiB
✅	agent_suse_arm64_fips	692.153 MiB
✅	docker_agent_amd64	818.833 MiB
✅	docker_agent_arm64	819.642 MiB
✅	docker_agent_jmx_amd64	1009.731 MiB
✅	docker_agent_jmx_arm64	999.192 MiB
✅	docker_cluster_agent_amd64	210.475 MiB
✅	docker_cluster_agent_arm64	223.456 MiB
✅	docker_cws_instrumentation_amd64	7.439 MiB
✅	docker_cws_instrumentation_arm64	6.877 MiB
✅	docker_dogstatsd_amd64	39.482 MiB
✅	docker_dogstatsd_arm64	37.560 MiB
✅	docker_host_profiler_amd64	305.814 MiB
✅	docker_host_profiler_arm64	317.125 MiB
✅	dogstatsd_deb_amd64	30.224 MiB
✅	dogstatsd_deb_arm64	28.247 MiB
✅	dogstatsd_rpm_amd64	30.224 MiB
✅	dogstatsd_suse_amd64	30.224 MiB
✅	iot_agent_deb_amd64	46.475 MiB
✅	iot_agent_deb_arm64	43.127 MiB
✅	iot_agent_deb_armhf	43.910 MiB
✅	iot_agent_rpm_amd64	46.476 MiB
✅	iot_agent_suse_amd64	46.475 MiB

cit-pr-commenter-54b7da · 2026-08-17T09:54:03Z

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: 574e82fd-e651-4944-aa85-b7206a13cf40

Baseline: 92f6b05
Comparison: 27bef0b
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	+0.49	[-0.37, +1.35]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	+0.39	[+0.27, +0.51]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	+0.26	[+0.11, +0.40]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	+0.23	[+0.12, +0.34]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	+0.07	[-0.05, +0.18]	1	Logs bounds checks dashboard
➖	quality_gate_idle_all_features	memory utilization	-0.05	[-0.09, -0.01]	1	Logs bounds checks dashboard
➖	quality_gate_security_mean_fs_load	memory utilization	-0.06	[-0.13, +0.02]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	-0.45	[-0.69, -0.21]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	quality_gate_idle	intake_connections	10/10	4 = 4	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	172.10MiB ≤ 178MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	744.79KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	4 = 4	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	522.12MiB ≤ 538MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.13MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	17 ≤ 40	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	203.36MiB ≤ 229MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	264.17MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	350.34 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	19 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	406.38MiB ≤ 439MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	total_bytes_received	10/10	0.94GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_private_action_runner	memory_usage	10/10	73.12MiB ≤ 76MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	29.34 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	328.36MiB ≤ 335MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	66.49 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	305.62MiB ≤ 314MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	20.99 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	311.71MiB ≤ 343MiB	bounds checks dashboard

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:

Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.
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.
Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

quality_gate_security_mean_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_security_mean_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
quality_gate_idle, bounds check total_bytes_received: 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.
quality_gate_metrics_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
quality_gate_metrics_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_metrics_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
quality_gate_metrics_logs, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
quality_gate_security_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_security_idle, bounds check cpu_usage: 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_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
quality_gate_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_security_no_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_security_no_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.

…egister Register() wrote l.cfg, l.stats, and iterated l.modules without holding the loader mutex, racing with GetStats() which takes the lock and reads l.stats. The expvar server (started before StartServer returns) can serve the /debug/stats endpoint while Register is still in progress. Hold l.Lock() around the writes to l.cfg and l.stats, and snapshot the modules map entries before spawning updateModuleStats goroutines so they don't read the map after unlock. Found via a race-detector-enabled build in staging (see #54333).

pgimalac added qa/done QA done before merge and regressions are covered by tests changelog/no-changelog No changelog entry needed labels Aug 17, 2026

dd-octo-sts Bot added the internal Identify a non-fork PR label Aug 17, 2026

github-actions Bot added the short review PR is simple enough to be reviewed quickly label Aug 17, 2026

dd-octo-sts Bot added team/ebpf-platform team/agent-build labels Aug 17, 2026

chatgpt-codex-connector Bot reviewed Aug 17, 2026

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Comment thread pkg/system-probe/api/module/loader_test.go Outdated

pgimalac force-pushed the pgimalac/fix-system-probe-module-loader-race branch from 954ede3 to 27bef0b Compare August 17, 2026 11:07

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fix(system-probe): protect module loader registry with mutex during Register - #54950

fix(system-probe): protect module loader registry with mutex during Register#54950
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Fine details of change detection per experiment

Bounds Checks: ✅ Passed

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What does this PR do?

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Files inventory check summary

Results for datadog-agent_7.84.0~devel.git.224.27bef0b.pipeline.131302790-1_amd64.deb:

Results for datadog-iot-agent_7.84.0~devel.git.224.27bef0b.pipeline.131302790-1_amd64.deb:

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Static quality checks

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Regression Detector

Regression Detector Results

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

CI Pass/Fail Decision

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