Possible problem with utrace_control

[Roland McGrath]

You should use linux/wait.h or similar facilities rather than calling
schedule() and wake_up_process() directly.  This doesn't have anything to
do with utrace, it's just the clean practice for normal kinds of blocking
in the kernel, for a variety of reasons.  That has to do with how your
control thread blocks, which is just the normal set of issues for any
thread in kernel code.  You are using the lowest-level way of doing things,
which is not recommended--that's why various higher-level facilities exist.

The admonition to use utrace facilities for all blocks has to do with when
you make a traced thread block.  You are on the correct path in that regard.

The relevant parts of your scenario match what I described.  The race I
talked about between your control thread's utrace_control() and tracee
callbacks returning UTRACE_STOP explains what you are seeing.


Thanks,
Roland