Apache NuttX is a mature, real-time embedded operating system (RTOS) https://nuttx.apache.org/
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raiden00pl 58d1d9f9d6 drivers/usbdev/cdcacm: serialize the TX ring drain with the class spinlock
cdcacm_sndpacket() runs from task context and from the bulk IN
completion callback, which may be interrupt context.  cdcuart_dmasend()
advances the xmit tail non-atomically, so a completion arriving mid
setup re-sends the same region and advances the tail past the head,
re-transmitting a ring of stale data.

c497c5feb0 dropped the critical section that used to cover this.
Restore it with priv->lock held across the setup and EP_SUBMIT; the
submit must stay inside to keep request order.  cdcuart_dmasend() now
runs with the lock held, so its own acquisition is removed.

The race needs the writer to keep the ring non-empty across
completions, so it only appears at high sustained write rates.  On
nRF52840, 131072-byte writes were received as ~147600 bytes - one extra
CDCACM_TXBUFSIZE of stale data per hit.  With this change the host
receives exactly what was sent.

Assisted-by: Claude Code
Signed-off-by: raiden00pl <raiden00@railab.me>
2026-08-09 02:04:26 +08:00
.github build(deps): bump docker/login-action from 4.5.1 to 4.6.0 2026-08-05 12:38:32 +02:00
arch arch/mips/jz4780: Add hardware Random Number Generator (RNG) support 2026-08-08 15:03:44 -03:00
audio audio: limit the buffer count guard to shared ring requests 2026-08-05 07:58:53 +02:00
binfmt !arch/arm: Use r9 as the PIC base register. 2026-08-06 01:38:23 +08:00
boards boards/nrf53/thingy53: configure XOSC32MCAP 2026-08-08 14:43:09 -03:00
cmake cmake: fix installed application binaries to match Application.mk 2026-08-06 02:39:03 +08:00
crypto tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
Documentation drivers/analog: add digital potentiometer driver support 2026-08-08 18:37:08 +08:00
drivers drivers/usbdev/cdcacm: serialize the TX ring drain with the class spinlock 2026-08-09 02:04:26 +08:00
dummy build: add initial cmake build system 2023-07-08 13:50:48 +08:00
fs fs/fat: Restore the no-short-name marker when the name will not shorten. 2026-08-08 10:05:43 +02:00
graphics tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
include libs/libc/netdb: Size an answer header by its header, not by its union. 2026-08-08 15:02:15 -03:00
libs libs/libc/netdb: Size an answer header by its header, not by its union. 2026-08-08 15:02:15 -03:00
mm mm/ubsan: fix signed inline value decoding 2026-07-30 12:52:17 +02:00
net net/igmp: fix checksum validation that always dropped valid IGMP packets 2026-08-07 16:36:42 +08:00
openamp tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
pass1 tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
sched sched/signal: Unblock sigtimedwait through kernel memory. 2026-08-08 14:59:21 -03:00
syscall syscall: add missing memory locking and clock_getres entries 2026-08-08 18:19:27 +08:00
tools !arch/arm: Use r9 as the PIC base register. 2026-08-06 01:38:23 +08:00
video tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
wireless tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
.asf.yaml github: master branch protection tune. 2025-05-07 18:37:13 -05:00
.codespell-ignore-lines arch/arm: Reserve r10 via ARCHCFLAGS and hoist the PIC module flags. 2026-07-24 23:09:08 +08:00
.codespellrc arch/arm/rp23xx: Add hardware TRNG driver for /dev/random. 2026-07-25 15:06:56 +08:00
.editorconfig .editorconfig: fix character encoding property specification 2025-11-28 19:12:13 +08:00
.gitignore git: Specify multiple build directories in .gitignore. 2026-05-20 03:06:58 +08:00
.gitmessage docs/contributing: Add a commit message template 2025-06-03 17:33:24 +08:00
.pre-commit-config.yaml pre-commit: enable codespell checks 2025-05-05 12:34:39 +08:00
.yamllint feat: add a GitHub action to lint the YAML files 2020-12-15 09:52:04 -06:00
AUTHORS AUTHORS: add Eren Terzioglu 2026-05-20 15:17:00 +08:00
CMakeLists.txt cmake: Do not link an executable to detect the compiler. 2026-07-25 22:52:39 +08:00
CONTRIBUTING.md contributing: Add requirement for 'Assisted-by' commit field 2026-07-12 09:42:28 +08:00
INVIOLABLES.md INVIOLABLES.md: Fix a simple alignment and change occurrences of Nuttx 2020-09-03 01:33:05 +08:00
Kconfig sched/misc/assert: Add CONFIG_SCHED_DUMP_TASKS and CONFIG_SCHED_DUMP_STACK 2026-06-09 08:04:54 -04:00
LICENSE libs/libdsp: Add Matrix operations 2026-07-11 14:55:59 -03:00
Makefile !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-09 22:41:11 +08:00
NOTICE Remove the double blank line from source files 2022-02-20 20:10:14 +01:00
README.md ci/testing: Add MemBrowse Integration 2026-06-18 12:07:41 -03:00
ReleaseNotes Documentation: move ReleaseNotes 2023-09-26 20:41:00 +08:00

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Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.

Getting Started

First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.

Documentation

You can find the current NuttX documentation on the Documentation Page.

Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.

The old NuttX documentation is still available in the Apache wiki.

Supported Boards

NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.

Contributing

If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.

License

The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.