Safer cleanup on SIGTERM#366
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Replace the popen()-based approach with fork()+execv("/bin/rm") called
directly from the signal handler. Both are async-signal-safe, and this
avoids the persistent child process per R session as well as the
envvar-expansion-at-runtime concern (R_SESSION_TMPDIR is now captured
into a static buffer at handler installation time).
Drop tests that verified the persistent child process lifecycle, and add
a poll_until() in the process-tree test to account for the rm child now
being spawned at signal time rather than pre-started.
Seem hard to make them work.
Instead of reimplementing it.
'poll' refers to the Unix system call in the processx codebase.
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Sorry for the long wait! I finally bit the bullet on this, but I used a different approach, because running an extra process does not seem right to me. |
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This makes the SIGTERM handler safer because
system()is not safe to call from a signal handler (see https://sourceware.org/bugzilla/show_bug.cgi?id=4737). To avoid doing too much work in the handler, we prepare a cleanup process ahead of time that we can trigger from the SIGTERM handler with an async-safe one-byte write.I'm a bit uneasy about calling
rm -rfon an envvar though. Should we use the previous approach of queryingtempdir()to create anrm -rfcommand ahead of time?