[Backport v4.4-branch] Bluetooth: Host: Introduce a general purpose Bluetooth workqueue - #116534
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[Backport v4.4-branch] Bluetooth: Host: Introduce a general purpose Bluetooth workqueue#116534d3zd3z wants to merge 4 commits into
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Remove the BT_RECV_CONTEXT Kconfig choice and its BT_RECV_WORKQ_SYS and BT_RECV_WORKQ_BT options. Low-priority HCI packets now always run on the dedicated Bluetooth RX workqueue. BT_RECV_WORKQ_SYS existed to save the RX thread stack on memory-constrained targets, primarily nRF51. Removing the alternate path simplifies the host threading model and removes a configuration-dependent RX context and its associated test matrix. The following commit retunes the affected in-tree nRF51 sample configurations. This breaking Kconfig change is tracked by RFC #113007. Update the public GATT callback context documentation, release notes and migration guide, and remove tests specific to the system-workqueue RX path. [davidb: dropped the 4.5 release notes and migration guide entries, which this branch does not carry, and applied the twister removals to the testcase.yaml files, which is what these test lists are named here] Assisted-by: Claude:claude-fable-5 Assisted-By: Claude:opus-5 Signed-off-by: Johan Hedberg <johan.hedberg@silabs.com> (cherry picked from commit 3b379ec) Signed-off-by: David Brown <david.brown@linaro.org>
With the removal of the BT_RECV_CONTEXT choice, nRF51 no longer processes low-priority HCI packets on the system workqueue; a dedicated Bluetooth RX thread is now always created. Adapt the bbc_microbit configurations built in CI to fit the 16 KB SRAM: - Size the RX thread through CONFIG_BT_RX_STACK_SIZE instead of relying on the system workqueue stack. - Shrink CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE, since low-priority RX no longer runs on it. - Preserve the controller ISR stack requirements and trim other options based on measured need. [davidb: applied the observer twister change to sample.yaml, which is what that test list is named on this branch] Assisted-by: Claude:claude-fable-5 Assisted-By: Claude:opus-5 Signed-off-by: Johan Hedberg <johan.hedberg@silabs.com> (cherry picked from commit 73c16a3) Signed-off-by: David Brown <david.brown@linaro.org>
Add bt_work_submit(), bt_work_schedule() and bt_work_reschedule() helpers that submit internal host work to the dedicated Bluetooth RX workqueue instead of the shared system workqueue. Start the workqueue on the first bt_enable() call and keep it alive for the lifetime of the system. Delayable host work can outlive an individual Bluetooth enable/disable cycle, so aborting and reinitializing the queue could strand work item state. The RX thread abort that bt_disable() used to perform is replaced with a graceful equivalent: before resetting and closing the transport, bt_disable() now stops queuing new low-priority HCI packets, discards the ones already queued, and cancels the RX work synchronously. An in-flight RX work item is thereby waited for while the transport is still able to serve any HCI commands it may issue, and a packet that slips into the queue during the teardown is dropped by the handler instead of being dispatched after the transport is gone. Unlike the abort, this cannot terminate the RX handler mid-execution with a buffer still referenced. The RX workqueue and dedicated TX processor thread are intentionally kept separate. Merging them would allow a blocking application callback in the RX context to stall command processing and reintroduce the deadlock the TX processor thread was created to avoid. Subsequent commits migrate selected delayed and immediate host work items to these helpers. Assisted-by: Claude:claude-fable-5 Assisted-By: Claude:opus-5 Signed-off-by: Johan Hedberg <johan.hedberg@silabs.com> (cherry picked from commit 9ef7acd) Signed-off-by: David Brown <david.brown@linaro.org>
Migrate the LE host's internal work items from the system workqueue to the dedicated Bluetooth workqueue by using the bt_work_schedule(), bt_work_reschedule() and bt_work_submit() helpers. This covers advertising (limited advertising timeout), ATT (channel timeout, EATT connection work), connections (deferred work and auto-initiated procedures), GATT (service changed, delayed store, database hash, multiple notifications), identity (RPA update), L2CAP (RTX and RX work), settings (ID and IRK store), and SMP (timeout). Migrating the per-connection deferred work is what keeps the existing teardown code correct: that work item performs the L2CAP channel and profile teardown (including the ATT and SMP disconnected callbacks), and the non-blocking k_work_cancel*() calls in those paths only reliably stop a concurrently running work item when both run on the same workqueue. Keeping teardown on the system workqueue while the canceled work items run on the Bluetooth workqueue would turn those cancellations into races. For the same reason the SMP timeout moves along with it. Additionally, cancel a dynamic L2CAP channel's RX work in l2cap_chan_destroy() so that a queued work item cannot be left behind with a reference to a channel object that the application may free or re-use after teardown. Update the id and conn host unit test mocks accordingly: id.c now uses bt_work_schedule() and conn.c uses bt_work_submit(), bt_work_schedule() and bt_work_reschedule(), so add fakes for these to the respective hci_core.c mocks (and drop the now-unused k_work_schedule() and k_work_reschedule() fakes from the kernel mocks). Assisted-by: Claude:claude-fable-5 Signed-off-by: Johan Hedberg <johan.hedberg@silabs.com> (cherry picked from commit 22896cb) Signed-off-by: David Brown <david.brown@linaro.org>
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area: Bluetooth
area: Bluetooth Mesh
area: Bluetooth Host
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August 17, 2026 20:38
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Pull request overview
This backport aligns the v4.4 Bluetooth Host with upstream behavior by introducing an unconditional, general-purpose Bluetooth RX workqueue and routing selected internal Host work items onto it to reduce interference with the shared system workqueue and to improve teardown/cancellation correctness.
Changes:
- Introduces
bt_work_submit/schedule/reschedule()helpers and a dedicated Bluetooth workqueue that is started once and kept alive across enable/disable cycles. - Migrates multiple Host internal work items (immediate and delayable) from the system workqueue to the Bluetooth workqueue and updates teardown behavior in
bt_disable(). - Removes
CONFIG_BT_RECV_CONTEXT/CONFIG_BT_RECV_WORKQ_{SYS,BT}configuration paths and updates tests/samples/docs accordingly.
Reviewed changes
Copilot reviewed 28 out of 28 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| tests/bsim/bluetooth/host/misc/conn_stress/central/prj.conf | Removes obsolete BT RX workqueue selection config/comments. |
| tests/bsim/bluetooth/host/l2cap/stress/tests_scripts/l2cap_syswq.sh | Deletes syswq-specific stress runner script now that selection is removed. |
| tests/bsim/bluetooth/host/l2cap/stress/testcase.yaml | Removes syswq-specific stress testcase entry. |
| tests/bsim/bluetooth/host/l2cap/stress/overlay-syswq.conf | Removes syswq overlay config that no longer applies. |
| tests/bluetooth/init/testcase.yaml | Removes a test case that toggled the removed BT RX context option. |
| tests/bluetooth/host/id/mocks/kernel.h | Updates unit-test fakes to match new work submission/scheduling usage. |
| tests/bluetooth/host/id/mocks/kernel.c | Updates unit-test fake definitions to match header changes. |
| tests/bluetooth/host/id/mocks/hci_core.h | Adds fake for bt_work_schedule() used by the Host after migration. |
| tests/bluetooth/host/id/mocks/hci_core.c | Adds fake implementation for bt_work_schedule(). |
| tests/bluetooth/host/conn/mocks/kernel.h | Drops fakes for k_work_{schedule,reschedule} that are no longer used by the migrated codepaths. |
| tests/bluetooth/host/conn/mocks/kernel.c | Drops matching fake definitions for removed kernel work scheduling fakes. |
| tests/bluetooth/host/conn/mocks/hci_core.h | Adds fakes for bt_work_{submit,schedule,reschedule} for migrated Host paths. |
| tests/bluetooth/host/conn/mocks/hci_core.c | Adds fake implementations for bt_work_{submit,schedule,reschedule}. |
| subsys/bluetooth/host/smp.c | Moves SMP timeout rescheduling onto the Bluetooth workqueue helper. |
| subsys/bluetooth/host/settings.c | Moves settings store work items onto the Bluetooth workqueue helper. |
| subsys/bluetooth/host/l2cap.c | Routes RX/RTX-related work onto Bluetooth workqueue; adds RX work cancellation in channel destroy. |
| subsys/bluetooth/host/Kconfig | Removes CONFIG_BT_RECV_CONTEXT choice/options. |
| subsys/bluetooth/host/id.c | Migrates RPA update scheduling to bt_work_schedule(). |
| subsys/bluetooth/host/hci_core.h | Declares bt_work_* helper APIs for internal Host use. |
| subsys/bluetooth/host/hci_core.c | Implements Bluetooth workqueue and helpers; updates RX queue handling and bt_disable() teardown. |
| subsys/bluetooth/host/gatt.c | Migrates several GATT delayed works to bt_work_{schedule,reschedule}. |
| subsys/bluetooth/host/conn.c | Moves connection deferred work submission/scheduling to Bluetooth workqueue helpers. |
| subsys/bluetooth/host/att.c | Migrates ATT/EATT delayable rescheduling to Bluetooth workqueue helpers. |
| subsys/bluetooth/host/adv.c | Migrates limited advertising timeout rescheduling to Bluetooth workqueue helpers. |
| samples/bluetooth/observer/sample.yaml | Adjusts test config to accommodate the always-on dedicated Bluetooth RX thread on micro:bit. |
| samples/bluetooth/observer/overlay_bbc_microbit-bt_ll_sw_split.conf | Rebalances stack sizes (ISR/syswq/BT RX) for micro:bit RAM constraints. |
| samples/bluetooth/mesh_demo/boards/bbc_microbit.conf | Adjusts stack sizes and buffer counts to fit with dedicated BT RX thread. |
| include/zephyr/bluetooth/gatt.h | Updates documentation to reflect callbacks now running in Bluetooth RX thread context. |
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| /* Make sure the RX work is not left queued with a reference to a | ||
| * channel object that may be freed or re-used after this call. | ||
| */ | ||
| (void)k_work_cancel(&le_chan->rx_work); | ||
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Backport of the fix from #93033 to
v4.4-branch.Fixes: #116523