Re: [Xen-cim] Emailing: libxen.diff

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

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);
>  }

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