Re: [libvirt] [PATCH] virBitmapFree: Change the function to a macro

-----Original Message----- From: Daniel P. Berrange [mailto:berrange@redhat.com] Sent: Monday, September 09, 2013 7:26 PM To: Liuji (Jeremy) Cc: libvir-list(a)redhat.com; Jinbo (Justin); Luohao (brian); Haofeng Subject: Re: [libvirt] [PATCH] virBitmapFree: Change the function to a macro On Mon, Sep 09, 2013 at 01:39:42AM +0000, Liuji (Jeremy) wrote: > > -----Original Message----- > > From: Daniel P. Berrange [mailto:berrange@redhat.com] > > Sent: Friday, September 06, 2013 6:37 PM > > To: Liuji (Jeremy) > > Cc: libvir-list(a)redhat.com; Jinbo (Justin); Luohao (brian); Haofeng > > Subject: Re: [libvirt] [PATCH] virBitmapFree: Change the function to a macro > > > > On Fri, Sep 06, 2013 at 10:30:56AM +0000, Liuji (Jeremy) wrote: > > > The parameter of virBitmapFree function is just a pointer, not a pointer of > > pointer. > > > The second VIR_FREE on virBitmapFree only assign NULL to the formal > > parameter. > > > After calling the virBitmapFree function, the actual parameter are still not > > NULL. > > > There are many code segment don't assign NULL to the formal parameter > > after calling > > > the virBitmapFree function. This will bring potential risks. > > > > > > A problem scenario: > > > 1) The XML of VM contain the below segment: > > > <numatune> > > > <memory mode='preferred' placement='auto' nodeset='0'/> > > > </numatune> > > > 2)virsh create the VM > > > 3)In the virDomainDefParseXML funtion: > > > /* Ignore 'nodeset' if 'placement' is 'auto' finally */ > > > if (placement_mode == > > VIR_NUMA_TUNE_MEM_PLACEMENT_MODE_AUTO) { > > > > > virBitmapFree(def->numatune.memory.nodemask); > > > def->numatune.memory.nodemask = NULL; > > > } > > > 4)Then, virsh destroy the VM. In the virDomainDefFree funtion, it also call the > > > virBitmapFree function to free the nodemask: > > > virBitmapFree(def->numatune.memory.nodemask); > > > But after this call, the value of def->numatune.memory.nodemask is still not > > NULL. > > > This will generate an exception. > > > > Have you got an actual crash happening today, or is this just a theoretical > > problem you're trying to address ? > > Yes，it's an actual crash problem. I found the problem in the above problem scenario in my first mail. Then can you send a patch which explicitly fixes that problem on its own, without doing this major refactoring, which obscures what is being fixed.