Question

I’m working on a project and cannot find any documentation that verifies signal/thread behavior for the following case.

I need to ensure that signals generated in a thread will be delivered by the offending thread (namely, SIGSEGV). I’ve been told that POSIX doesn’t ensure this behavior and that pthreads, for example, can generate signals in pthread 1 yet have the signal delivered in pthread 2. Therefore, I’m planning on using clone(2) to have finer control of signal/thread behavior, but still cannot find documentation in the man pages that ensures signals will be delivered by the offending thread.

Hardcore systems programmers: any documentation or insights would be very much appreciated!

Answer 1

The POSIX chapter on Signal Generation and Delivery states that:

At the time of generation, a
determination shall be made whether
the signal has been generated for the
process or for a specific thread
within the process. Signals which are
generated by some action attributable
to a particular thread, such as a
hardware fault, shall be generated for
the thread that caused the signal to
be generated. Signals that are
generated in association with a
process ID or process group ID or an
asynchronous event, such as terminal
activity, shall be generated for the
process.

A synchronous SIGSEGV caused by an incorrect memory access in a thread is clearly such a signal “…generated by some action attributable to a particular thread…”, so they are guaranteed to be generated for the offending thread (which means handled or ignored by that thread, as appropriate).