Re: [libvirt] [PATCH 1/2] Java bindings for domain events
On Wed, Nov 19, 2008 at 11:22:31AM -0500, David Lively wrote:
On Wed, 2008-11-19 at 10:35 -0500, David Lively wrote:
> The patch already synchronizes operations using virConnect objects with
> each other. To avoid making illegal EventImpl callbacks from Java for
> the current libvirt, I have to lock every Connect object known to Java
> and hold off creating new connections (via open & friends) around an
> EventImpl callback. This sounds rather appalling to me, but it's
> starting to sound like the only practical route in the short term
> (unless it turns out we can rely on pthreads in WIN32 ...).
Hmmm ... maybe the less appalling :-) route is practical. Currently, we
require only the Windows equivalent of a simple pthread mutex. We just
need to support declaration, initialization, lock, unlock, and
destruction, something like the following (thanks to Tom Hazel for
pointing me to the Windows Mutex stuff):
#if (defined _WIN32 || defined __WIN32__)
#define PTHREAD_MUTEX_T(v) HANDLE v
#define pthread_mutex_init(lk,p) ((*(lk)) = CreateMutex(0, FALSE, 0))
#define pthread_mutex_destroy(lk) CloseHandle(*(lk))
#define pthread_mutex_lock(lk) WaitForSingleObject(*(lk), INFINITE)
#define pthread_mutex_unlock(lk) ReleaseMutex(*(lk))
#define pthread_sigmask(h, s, o) sigprocmask((h), (s), (o))
#endif
I'm not a Windows guy, so maybe I'm missing something. But this doesn't
seem like a Big Deal ...
note that libxml2 that we rely on has a fully ported mutex basic API
in libxml/threads.h
/*
* xmlMutex are a simple mutual exception locks.
*/
typedef struct _xmlMutex xmlMutex;
typedef xmlMutex *xmlMutexPtr;
/*
* xmlRMutex are reentrant mutual exception locks.
*/
typedef struct _xmlRMutex xmlRMutex;
typedef xmlRMutex *xmlRMutexPtr;
XMLPUBFUN xmlMutexPtr XMLCALL
xmlNewMutex (void);
XMLPUBFUN void XMLCALL
xmlMutexLock (xmlMutexPtr tok);
XMLPUBFUN void XMLCALL
xmlMutexUnlock (xmlMutexPtr tok);
XMLPUBFUN void XMLCALL
xmlFreeMutex (xmlMutexPtr tok);
XMLPUBFUN xmlRMutexPtr XMLCALL
xmlNewRMutex (void);
XMLPUBFUN void XMLCALL
xmlRMutexLock (xmlRMutexPtr tok);
XMLPUBFUN void XMLCALL
xmlRMutexUnlock (xmlRMutexPtr tok);
XMLPUBFUN void XMLCALL
xmlFreeRMutex (xmlRMutexPtr tok);
in case you really want to do the exclusive locking at the C level
while still being portable.
Still it's probably better to try to implement most of this at the
Java level, at least IMHO,
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel(a)veillard.com | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/