Internal tracing mechanism

BK Internal Tracing. How to instrument the code to be able to track what is going on in a multi process setup.

The core of the code is in src/libc/utils/trace.c

To use, set up an environment variable. If set to an absolute path, the output will be put in a file. Other wise it will be put to /dev/tty, and if that doesn’t work, stderr (well, not stderr, but unbuffered fd = 2).

The env variables, in order they are tested (first one used):

BK_DTRACE - terse (please fill in what that means) BK_TTRACE - time trace BK_TRACE - trace with pid

Also supporting the operations to limit what is traced are env variables set to a colon separated list of …​

BK_TRACE_PROGS - prog variable (av[0]) globs BK_TRACE_FILES - file globs BK_TRACE_FUNCS - func globs

Under the hood…​

Trace uses efopen(), which takes an env variable, and if it is an absolute path, writes in it, and if not, then tries to open TTY and if it can’t, just writes to stderr (really, unbuffered fd = 2).