csighandler3: try a fallback interpreter if none in TLS #22530
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If an external library, possibly loaded by an XS module, creates a thread, perl has no control over this thread, nor does it create an interpreter for that thread, so if a signal is delivered to that thread my_perl would be NULL, and we would crash trying to safely deliver the signal. To avoid that uses the saved main interpreter pointer instead. Since trying to unsafe deliver the signal to the handler from the wrong thread would result in races on the interpreter's data structures I chose not to direct deliver unsafe signals. Accessing PL_psig_pend[] from the wrong thread isn't great, but to ensure safe handling of that we'd need lockless atomics, which we don't have access to from C99 (and aren't required in C11). Fixes Perl#22487
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I'm wondering if a |
Maybe, but Win32 already does something like my patch, Ctrl-C events are delivered in a separate thread, and PERL_GET_SIG_CONTEXT aka win32_signal_context() sets the the context for the current thread from PL_curinterp and expects Perl_csighandler3 to deal with it. Right now I don't see a direct way for us to get the main thread ID/handle. That's something I'd need to add to |
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If an external library, possibly loaded by an XS module, creates a thread, perl has no control over this thread, nor does it create an interpreter for that thread, so if a signal is delivered to that thread my_perl would be NULL, and we would crash trying to safely deliver the signal.
To avoid that uses the saved main interpreter pointer instead.
Since trying to unsafe deliver the signal to the handler from the wrong thread would result in races on the interpreter's data structures I chose not to direct deliver unsafe signals.
Accessing PL_psig_pend[] from the wrong thread isn't great, but to ensure safe handling of that we'd need lockless atomics, which we don't have access to from C99 (and aren't required in C11).
Fixes #22487