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This patch fixes a few really hard problems wrt PID files:
1. Listening for IN_CREATE events means we get notified immediately by
the kernel when someone calls open()/fopen() on a PID file. Reading
the contents returns 0, thank you atoi() ... so we drop IN_CREATE
and instead look for IN_CLOSE_WRITE, there fixed it! Not quite ...
2. Some programs, like Zebra, and other Quagga/Frr daemons, don't
close() their PID files after creation. Instead they ftruncate()
and keep them open, and locked. Presumably to get a mechanism to
detect already running instances -- messes life up a bit for the
rest of us though. So we need to read files after IN_MODIFY too.
3. We also want to track IN_DELETE so we can deassert conditions when
services exit gracefully and clean up their PID files
The rest fo the commit is debug instrumentation changes.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>