On Tue, Feb 07, 2017 at 02:43:17PM +0800, Eli Qiao wrote: > On Tuesday, 7 February 2017 at 12:11 AM, Daniel P. Berrange wrote: > > > On Mon, Feb 06, 2017 at 10:23:36AM +0800, Eli Qiao wrote: > > > This patch adds some utils struct and functions to expose resctrl > > > information. > > > > > > virResCtrlAvailable: If resctrl interface exist on host > > > virResCtrlGet: get specify type resource contral information > > > virResCtrlInit: initialize resctrl struct from the host's sys fs. > > > ResCtrlAll[]: an array to maintain resource control information. > > > > > > Signed-off-by: Eli Qiao <liyong.qiao@xxxxxxxxx (mailto:liyong.qiao@xxxxxxxxx)> > > > --- > > > +}; > > > + > > > + > > > +typedef struct _virResCacheBank virResCacheBank; > > > +typedef virResCacheBank *virResCacheBankPtr; > > > +struct _virResCacheBank { > > > + unsigned int host_id; > > > + unsigned long long cache_size; > > > + unsigned long long cache_left; > > > + unsigned long long cache_min; > > > + virBitmapPtr cpu_mask; > > > +}; > > > > > > > > > > +typedef struct _virResCtrl virResCtrl; > > > +typedef virResCtrl *virResCtrlPtr; > > > +struct _virResCtrl { > > > + bool enabled; > > > + const char *name; > > > + int num_closid; > > > + int cbm_len; > > > + int min_cbm_bits; > > > + const char* cache_level; > > > + int num_banks; > > > + virResCacheBankPtr cache_banks; > > > +}; > > > > > > > > > Can any of these fields change at runtime, or are they all > > immutable once populated. > > Only cache_banks will be change at runtime, such as cache_left > on each socket will be updated if libvirt allocates cache to domains. Ok, so the API is returning a direct point to the virResCtrlPtr struct and there's no locking here. So if cache_banks struct contents changes while some caller is reading the virResCtrlPtr struct we have race problems. I'd suggest that best option is probably to take the mutable cache_left field *out* of the struct. That lets the callers treat the entire struct as immutable. Then add a separate API to explicitly query the cache_left value - only that api needs to do locking to return a consistent point-in-time view of the cache_left value. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
