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hci_le_conn_failed() unconditionally calls hci_enable_advertising(), although its own comment states advertising should be re-enabled only when the failed attempt was made as a peripheral. hci_le_conn_failed() is reached from hci_conn_failed() for every failed LE connection, including outgoing central connections. For a central attempt this enable is redundant: hci_le_create_conn_sync() already restores advertising via hci_resume_advertising_sync() in its done: block. Because hci_enable_advertising() only queues the work on cmd_sync_work, it runs *after* that resume has already succeeded and set HCI_LE_ADV. The resulting HCI sequence, captured on a BCM43455 (no LE Extended Advertising, so legacy advertising is used): LE Create Connection Status Success ... 13.8 s, peer never answers ... LE Set Advertising Parameters (0x2006) Success <- done: resume, LE Set Advertising Enable (0x200a) Success HCI_LE_ADV set LE Create Connection Cancel (0x200e) Success LE Connection Complete Unknown Conn Id LE Set Advertising Parameters (0x2006) Command Disallowed (0x0c) The last command is the queued enable from hci_le_conn_failed() running as a second hci_enable_advertising_sync() pass. It clears HCI_LE_ADV (hci_sync.c, "Clear the HCI_LE_ADV bit temporarily"), then sends LE Set Advertising Parameters while the controller is still advertising, which the controller correctly rejects with Command Disallowed. The disable-first call at the top of hci_enable_advertising_sync() cannot prevent this: hci_disable_advertising_sync() returns early without sending anything when HCI_LE_ADV is clear, so it is a no-op exactly when the flag is wrong. hci_enable_advertising_sync() then returns without sending LE Set Advertising Enable, so HCI_LE_ADV is never set again. The legacy software rotation loop re-arms hci_schedule_adv_instance_sync() every HCI_DEFAULT_ADV_DURATION (2 s), and its "already advertising" shortcut tests HCI_LE_ADV, which can no longer become true. The command is therefore retried every 2 s indefinitely: Bluetooth: hci0: Opcode 0x2006 failed: -16 Observed on a gateway as 5326 occurrences over 3 hours, ending only when bluetoothd was restarted. Connection attempts that succeed do not call hci_le_conn_failed() and never trigger this. Add the role test the comment already describes. Both other hci_enable_advertising() call sites reached from a failed/closed LE connection (hci_cs_disconnect() and hci_disconn_complete_evt()) already guard on conn->role == HCI_ROLE_SLAVE; this one was missed. Reproducing needs legacy advertising (ext_adv_capable() false, so the software rotation loop is used), simultaneous peripheral advertising and outgoing central connects, and a central connect that times out rather than failing fast. The Fixes tag points at the commit that introduced the advertising restart into this path for the directed-advertising (peripheral) case; the role test that the later commit |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. 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