Re: [Libguestfs] [PATCH nbdkit 1/2] vddk: Relax threading model: SERIALIZE_ALL_REQUESTS -> SERIALIZE_REQUESTS.

On Thu, Aug 6, 2020, 16:16 Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > See comment in code and > https://www.redhat.com/archives/libguestfs/2020-August/msg00023.html > --- > plugins/vddk/vddk.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/plugins/vddk/vddk.c b/plugins/vddk/vddk.c > index c24da96f..5926e181 100644 > --- a/plugins/vddk/vddk.c > +++ b/plugins/vddk/vddk.c > @@ -478,11 +478,18 @@ vddk_dump_plugin (void) > #endif > } > > -/* XXX To really do threading correctly in accordance with the VDDK > - * documentation, we must do all open/close calls from a single > - * thread. This is a huge pain. > +/* The rules on threads and VDDK are here: > + * > https://code.vmware.com/docs/11750/virtual-disk-development-kit-programmi... > + * > + * Before nbdkit 1.22 we used SERIALIZE_ALL_REQUESTS. Since nbdkit > + * 1.22 we changed this to SERIALIZE_REQUESTS and added a mutex around > + * calls to VixDiskLib_Open and VixDiskLib_Close. This is not quite > + * within the letter of the rules, but is within the spirit. > The document is very clear about using the same thread for open an close. Using a lock is not the same.

I think Eric already wrote about this. */ > -#define THREAD_MODEL NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS > +#define THREAD_MODEL NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS > + > +/* Lock protecting open/close calls - see above. */ > +static pthread_mutex_t open_close_lock = PTHREAD_MUTEX_INITIALIZER; > > /* The per-connection handle. */ > struct vddk_handle { > @@ -524,6 +531,7 @@ free_connect_params (VixDiskLibConnectParams *params) > static void * > vddk_open (int readonly) > { > + ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&open_close_lock); > struct vddk_handle *h; > VixError err; > uint32_t flags; > @@ -616,6 +624,7 @@ vddk_open (int readonly) > static void > vddk_close (void *handle) > { > + ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&open_close_lock); > struct vddk_handle *h = handle; > > DEBUG_CALL ("VixDiskLib_Close", "handle"); > -- > 2.27.0 > >