[Libvirt-cim] [PATCH] (#2) Workaround to fix race condition around libvirt init

[Sharad Mishra]

pushed

Sharad Mishra
Open Virtualization
Linux Technology Center
IBM

"Eduardo Lima (Etrunko)" <eblima at linux.vnet.ibm.com> wrote on 08/31/2011
06:41:56 AM:

> "Eduardo Lima (Etrunko)" <eblima at linux.vnet.ibm.com>
> 08/31/2011 06:41 AM
>
> Please respond to
> eblima at br.ibm.com
>
> To
>
> List for discussion and development of libvirt CIM
<libvirt-cim at redhat.com>
>
> cc
>
> Sharad Mishra/Beaverton/IBM at IBMUS
>
> Subject
>
> Re: [Libvirt-cim] [PATCH] (#2) Workaround to fix race condition
> around libvirt init
>
> On 08/30/2011 02:14 PM, Sharad Mishra wrote:
> > # HG changeset patch
> > # User Sharad Mishra<snmishra at us.ibm.com>
> > # Date 1314719316 25200
> > # Node ID c54aafd0b2c6414f91b96bc30e2f148bb78d5c59
> > # Parent  277b56b3863b5f81a3faa18aeb7b9951b963b489
> > (#2) Workaround to fix race condition around libvirt init.
> >
> > This patch fixes the race condition caused when mutiple
> > threads try to start VMs at the same time. This patch
> > also fixes the issue of incorrect mem allocation for
> > VSSD property - emulator.
> >
> > #2: included Edurdo's patch for make_space
> >      took care of coding guidelines.
> >
> > Signed-off-by: Sharad Mishra<snmishra at us.ibm.com>
> >
> > diff --git a/libxkutil/misc_util.c b/libxkutil/misc_util.c
> > --- a/libxkutil/misc_util.c
> > +++ b/libxkutil/misc_util.c
> > @@ -28,6 +28,7 @@
> >   #include<stdbool.h>
> >   #include<stdarg.h>
> >   #include<unistd.h>
> > +#include<pthread.h>
> >   #include<libvirt/libvirt.h>
> >   #include<libvirt/virterror.h>
> >
> > @@ -45,6 +46,9 @@
> >   #include "misc_util.h"
> >   #include "cs_util.h"
> >
> > +static pthread_mutex_t libvirt_mutex = PTHREAD_MUTEX_INITIALIZER;
> > +/* libvirt library not initialized */
> > +static int libvirt_initialized = 0;
> >
> >   #define URI_ENV "HYPURI"
> >
> > @@ -114,11 +118,15 @@
> >
> >           CU_DEBUG("Connecting to libvirt with uri `%s'", uri);
> >
> > +        pthread_mutex_lock(&libvirt_mutex);
> > +
> >           if (is_read_only())
> >                   conn = virConnectOpenReadOnly(uri);
> >           else
> >                   conn = virConnectOpen(uri);
> >
> > +        pthread_mutex_unlock(&libvirt_mutex);
> > +
> >           if (!conn) {
> >                   CU_DEBUG("Unable to connect to `%s'", uri);
> >                   return NULL;
> > @@ -530,7 +538,19 @@
> >
> >   bool libvirt_cim_init(void)
> >   {
> > -        return virInitialize() == 0;
> > +        int ret = 0;
> > +
> > +        /* double-check lock pattern used for performance reasons */
> > +        if (libvirt_initialized == 0) {
> > +                pthread_mutex_lock(&libvirt_mutex);
> > +                if (libvirt_initialized == 0) {
> > +                        ret = virInitialize();
> > +                        if (ret == 0)
> > +                                libvirt_initialized = 1;
> > +                }
> > +                pthread_mutex_unlock(&libvirt_mutex);
> > +        }
> > +        return (ret == 0);
> >   }
> >
> >   bool check_refs_pfx_match(const CMPIObjectPath *refa,
> > diff --git a/src/Virt_VirtualSystemManagementService.c b/src/
> Virt_VirtualSystemManagementService.c
> > --- a/src/Virt_VirtualSystemManagementService.c
> > +++ b/src/Virt_VirtualSystemManagementService.c
> > @@ -188,6 +188,24 @@
> >           return 1;
> >   }
> >
> > +static bool make_space(struct virt_device **list, int cur, int new)
> > +{
> > +        struct virt_device *tmp;
> > +
> > +        tmp = calloc(cur + new, sizeof(*tmp));
> > +        if (tmp == NULL)
> > +                return false;
> > +
> > +        if (*list) {
> > +                memcpy(tmp, *list, sizeof(*tmp) * cur);
> > +                free(*list);
> > +        }
> > +
> > +        *list = tmp;
> > +
> > +        return true;
> > +}
> > +
> >   static bool fv_set_emulator(struct domain *domain,
> >                               const char *emu)
> >   {
> > @@ -198,6 +216,11 @@
> >           if (emu == NULL)
> >                   return true;
> >
> > +        if (!make_space(&domain->dev_emu, 0, 1)) {
> > +                CU_DEBUG("Failed to alloc disk list");
> > +                return false;
> > +        }
> > +
> >           cleanup_virt_device(domain->dev_emu);
> >
> >           domain->dev_emu->type = CIM_RES_TYPE_EMU;
> > @@ -1369,24 +1392,6 @@
> >           return msg;
> >   }
> >
> > -static bool make_space(struct virt_device **list, int cur, int new)
> > -{
> > -        struct virt_device *tmp;
> > -
> > -        tmp = calloc(cur + new, sizeof(*tmp));
> > -        if (tmp == NULL)
> > -                return false;
> > -
> > -        if (*list) {
> > -                memcpy(tmp, *list, sizeof(*tmp) * cur);
> > -                free(*list);
> > -        }
> > -
> > -        *list = tmp;
> > -
> > -        return true;
> > -}
> > -
> >   static char *add_device_nodup(struct virt_device *dev,
> >                                 struct virt_device *list,
> >                                 int max,
> >
>
> +1. Tricky stuff. :)
>
> --
> Eduardo de Barros Lima
> Software Engineer, Open Virtualization
> Linux Technology Center - IBM/Brazil
> eblima at br.ibm.com
>
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