Semaphore use in signals
Nobody has claimed this yet.
Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 35/100
- Issue type
- Feature
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- cpp
- Domain
- operating-systems
Research direction
No file or test is named. Start by tracing the semaphore implementations used by interprocess_semaphore, especially the spin and POSIX paths, and how timed_wait interacts with SIGINT. Done means the project has a settled design for a non-throwing POSIX post and compile-time signal-safety information.
Written by the indexing model from the issue text.
Description
I am using interprocess' semaphore in conjunction with timed_wait, and I need to be able to handle SIGINT to terminate the waiting early. Looking into the implementation, I can see that I am getting the spin semaphore internally, which suggests to me that post()ing it from the signal handler is safe, since it is effectively just an atomic increment.
This would likely not hold in other types of internal implementations of the semaphore. For example, while POSIX implementation seems to be fine in the first line (it just uses sem_post), it can later throw an exception.
This leads me to two thoughts:
- Can we have a variant of the POSIX post() that would not throw an exception?
- Can we add compile-time introspection for signal safety of the chosen semaphore implementation? So that one can do something like
static_assert(boost::interprocess::interprocess_semaphore::signal_safe_post).
I am happy to contribute such improvements if there's a consensus.
- Dominant language
- C++
- Stars
- 185
- Forks
- 131
- PR merge metrics
- No merged PRs in 30d
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