This commit beefs up the Makefile to do the build, instead of the
Rakefile.
It also removes from the Rakefile the dependency on rake_utils, which
should mean it's ok to build in a schroot.
The files are reorganised to make the Makefile rules more tractable,
although the reorganisation reveals a problem with our current code
organisation.
The problem is that the proxy-specific code transitively depends on the
server code via flexnbd.h, which has a circular dependency on the server
and client structs. This should be broken in a future commit by
separating the flexnbd struct into a shared config struct and
server-specific parts, so that the server code can be moved into
src/server to more accurately show the functional dependencies.
While the mirror mutex is taken, the mirroring can be abandoned and serve->mirror
set to NULL, so we need to lock around reading information from serve->mirror
This makes it easier for the tests (and supervisor) to guarantee to be
able to connect to the server socket.
Also this patch moves freeing the mirror supervisor into the server
thread.
Changing behaviour so that instead of rebinding after a successful
migration and continuing as an ordinary server, we simply quit with a
0 exit code and let our caller restart us as a server if they want to.
This means that everything in listen.c, listen.h, and anything making
reference to a rebind address is unneeded.
Now that we have 3 mutexes lying around, it's important that we check
and free these if necessary if error() is called in any thread that can
hold them. To do this, we now have flexthread.c, which defines a
flexthread_mutex struct. This is a wrapper around a pthread_mutex_t and
a pthread_t. The idea is that in the error handler, the thread can
check whether it holds the mutex and can free it if and only if it does.
This is important because pthread fast mutexes can be freed by *any*
thread, not just the thread which holds them.
Note: it is only ever safe for a thread to check if it holds the mutex
itself. It is *never* safe to check if another thread holds a mutex
without first locking that mutex, which makes the whole operation rather
pointless.
