Ewan,
It looks like if we can just do these inside _init and _fini (which are
functions called when the library is loaded and unloaded respectively),
we won't need to wory about MT-safeness. The OS won't unload the shared
library till everyone who's linked to it has unloaded.
Was there any specific reason why there were specific xen_init and
xen_fini calls created?
Raj
> -----Original Message-----
> From: Ewan Mellor [mailto:ewan@xxxxxxxxxxxxx]
> Sent: Saturday, December 23, 2006 5:13 AM
> To: Subrahmanian, Raj
> Cc: xen-cim@xxxxxxxxxxxxxxxxxxx; Jim Fehlig
> Subject: Re: [Xen-cim] Emailing: libxen.diff
>
> On Fri, Dec 22, 2006 at 10:00:49PM -0500, Subrahmanian, Raj wrote:
>
> > This will MT-safe the xen_init and xen_fini calls, so that
> we can do
> > it once for each provider than for each call.
>
> I don't think that this belongs in libxen, as that library
> shouldn't add a dependency on libpthread unconditionally.
> Can't you do this inside the provider?
>
> Ewan.
>
> > Raj
> > <<libxen.diff>>
>
> > diff -r 8348f40ba2b7 tools/libxen/Makefile
> > --- a/tools/libxen/Makefile Thu Dec 21 14:49:19 2006 +0000
> > +++ b/tools/libxen/Makefile Fri Dec 22 17:32:26 2006 -0500
> > @@ -27,7 +27,8 @@ CFLAGS = -Iinclude \
> > -W -Wall -Wmissing-prototypes -Werror -std=c99 -O2 -fPIC
> >
> > LDFLAGS = $(shell xml2-config --libs) \
> - $(shell curl-config --libs)
> > + $(shell curl-config --libs) \
> > + -lpthread
> >
> > LIBXENAPI_HDRS = $(wildcard include/*.h) LIBXENAPI_OBJS =
> $(patsubst
> > %.c, %.o, $(wildcard src/*.c)) diff -r 8348f40ba2b7
> > tools/libxen/include/xen_common.h
> > --- a/tools/libxen/include/xen_common.h Thu Dec 21
> 14:49:19 2006 +0000
> > +++ b/tools/libxen/include/xen_common.h Fri Dec 22
> 17:32:26 2006 -0500
> > @@ -24,13 +24,13 @@
> > #include <stddef.h>
> > #include <stdint.h>
> > #include <time.h>
> > -
> > +// The init and the fini really need to happen only once.
> > +// The mutex will take care of that
> > +#include <pthread.h>
> > #include "xen_host_decl.h"
> > -
> >
> > typedef bool (*xen_result_func)(const void *data, size_t len,
> > void *result_handle);
> > -
> >
> > /**
> > * len does not include a terminating \0.
> > diff -r 8348f40ba2b7 tools/libxen/src/xen_common.c
> > --- a/tools/libxen/src/xen_common.c Thu Dec 21 14:49:19 2006 +0000
> > +++ b/tools/libxen/src/xen_common.c Fri Dec 22 17:32:26 2006 -0500
> > @@ -43,6 +43,8 @@
> > #define PERMISSIVE 1
> >
> >
> > +static pthread_mutex_t mutexUserCount=PTHREAD_MUTEX_INITIALIZER;
> > +static unsigned UserCount=0;
> > static xmlXPathCompExprPtr responsePath = NULL; static
> > xmlXPathCompExprPtr faultPath = NULL;
> >
> > @@ -111,23 +113,35 @@ void
> > void
> > xen_init(void)
> > {
> > - responsePath =
> > - xmlXPathCompile(
> > - BAD_CAST(
> > -
> "/methodResponse/params/param/value/struct/member/value"));
> > - faultPath =
> > - xmlXPathCompile(
> > -
> BAD_CAST("/methodResponse/fault/value/struct/member/value"));
> > + pthread_mutex_lock(&mutexUserCount);
> > + if (UserCount==0)
> > + {
> > + responsePath =
> > + xmlXPathCompile(
> > + BAD_CAST(
> > +
> "/methodResponse/params/param/value/struct/member/value"));
> > + faultPath =
> > + xmlXPathCompile(
> > +
> BAD_CAST("/methodResponse/fault/value/struct/member/value"));
> > + }
> > + UserCount++;
> > + pthread_mutex_unlock(&mutexUserCount);
> > }
> >
> >
> > void
> > xen_fini(void)
> > {
> > - xmlXPathFreeCompExpr(responsePath);
> > - xmlXPathFreeCompExpr(faultPath);
> > - responsePath = NULL;
> > - faultPath = NULL;
> > + pthread_mutex_lock(&mutexUserCount);
> > + UserCount--;
> > + if (UserCount==0)
> > + {
> > + xmlXPathFreeCompExpr(responsePath);
> > + xmlXPathFreeCompExpr(faultPath);
> > + responsePath = NULL;
> > + faultPath = NULL;
> > + }
> > + pthread_mutex_unlock(&mutexUserCount);
> > }
>
> > _______________________________________________
> > Xen-cim mailing list
> > Xen-cim@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-cim
>
>
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