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| -rw-r--r-- | doc/bugs/signal_weirdness.mdwn | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/doc/bugs/signal_weirdness.mdwn b/doc/bugs/signal_weirdness.mdwn new file mode 100644 index 000000000..a31cc2148 --- /dev/null +++ b/doc/bugs/signal_weirdness.mdwn @@ -0,0 +1,38 @@ +For the record, there is a slight weirdness with how git-annex +handles a signal like ctrl-c. + +For example: + + joey@gnu:~/tmp/b>git annex copy a b --to origin + copy a (checking origin...) (to origin...) + SHA256-s104857600--20492a4d0d84f8beb1767f6616229f85d44c2827b64bdbfb260ee12fa1109e0e + 3272 0% 0.00kB/s 0:00:00 ^C + zsh: interrupt git annex copy a --to origin + joey@gnu:~/tmp/b> + rsync error: unexplained error (code 130) at rsync.c(549) [sender=3.0.9] + +Here git-annex exits before rsync has fully exited. Not a large problem +but sorta weird. + +The culprit is `safeSystemEnv` in Utility.SafeCommand, which installs +a default signal handler for SIGINT, which causes it to immediatly +terminate git-annex. rsync, in turn, has its own SIGINT handler, which +prints the message, typically later. + +(Why it prints that message and not its more usual message about having +received a signal, I'm not sure?) + +It's more usual for a `system` like thing to block SIGINT, letting the child +catch it and exit, and then detecting the child's exit status and terminating. +However, since rsync *is* trapping SIGINT, and exiting nonzero explicitly, +git-annex can't tell that rsync failed due to a SIGINT. +And, git-annex typically doesn't stop when a single child fails. In the +example above, it would go on to copy `b` after a ctrl-c! + +A further complication is that git-annex is itself a child process +of git, which does not block SIGINT either. So if git-annex blocks sigint, +it will be left running in the background after git exits, and continuing +with further actions too. (Probably this is a bug in git.) + +Which is why the current behavior of not blocking SIGINT was chosen, +as a less bad alternative. Still, I'd like to find a better one. --[[Joey]] |