My project for the 2024 edition of Google Summer of Code was done in collaboration with the RTEMS Project. RTEMS (Real-Time Executive for Multiprocessor Systems) is a real-time operating system (RTOS) designed for embedded systems. (More information can be found on the Project Page)
The goal of my project was to improve the POSIX compliance of the OS, specifically by working on the Asynchronous Input/Output (AIO) interface. My objective was to correct behaviors that did not comply with POSIX specifications and to implement missing features.
Overall, I’m satisfied with the work I accomplished this summer. Most of the tasks I planned have been successfully completed, although not all have been merged. There was more work than anticipated to implement missing features and correct issues in the existing functions. This, combined with an unexpected and difficult-to-diagnose error, led to my delay in fully completing lio_listio(). However, I plan to continue contributing even after GSoC to finish what I started.
Below is a table summarizing all completed and planned contributions. After the table, you’ll find a brief description of each contribution. For more detailed information, see the linked blog posts, which provide insights into the implementation and challenges.
| Contribution | Status | Related MR | Blog Posts |
|---|---|---|---|
| Review and merge existing patches | Completed | !40, !41, !42 | link |
Correct the behavior of aio_return() and aio_error() |
Completed | !85 | link |
Add support for O_DSYNC in aio_fsync() |
Completed | !128 | link |
| Add notification at request completion | Completed | !118 | link |
Implement lio_listio() |
Work in Progress | !188 | - |
Implement aio_suspend() |
Not Started | - | - |
| Update documentation | Completed | !56, !26, !44 | link |
This was my first contribution. I began by reviewing patches provided by my mentor to assess their relevance. This task didn’t involve writing much code, aside from fixing minor formatting issues. However, it helped me learn the RTEMS workflow and contribution process.
aio_return() and aio_error()This task aimed to correct the behavior of these functions, which were previously callable multiple times for the same operation—a violation of POSIX. The fix ensured correct behavior in line with the specification.
O_DSYNC in aio_fsync()The goal here was to implement support for the O_DSYNC flag in the aio_fsync() function. The function previously only accepted one synchronization type, so this update made it compliant with POSIX expectations.
POSIX requires the sigevent field in the aiocb structure to generate a notification when an I/O request completes. This field was previously ignored in RTEMS, so I implemented the necessary logic to support it.
lio_listio()This task involved implementing the missing lio_listio() function. The core work is mostly complete, but one issue remains unresolved before it can be merged.
aio_suspend()I planned to work on this after completing lio_listio(), but due to delays with that task, I wasn’t able to start it during the GSoC period.
This contribution includes updates to both Doxygen comments and the RTEMS API documentation, improving clarity and completeness.
This experience has been an invaluable learning opportunity. Before this summer, my programming experience was mostly limited to academic projects. These were small, short-lived, and often didn’t require tools like version control or professional debugging techniques.
Working on the RTEMS project was a completely different challenge. The large codebase forced me to improve my Git skills, learn proper debugging methods, and understand the importance of writing well-tested, maintainable code. I also had to write and run test coverage analysis (Dedicated Post about coverage).
I greatly improved my ability to understand unfamiliar code. When I first applied, I couldn’t fully grasp RTEMS project proposals. Now, I understand much of the structure, especially in the AIO area, and can follow conversations within the community.
Overall, GSoC helped me grow as a developer. I now feel more confident in my ability to contribute to large projects and to produce high-quality, collaborative code. These skills will be invaluable in my future career.