From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <434BB728.3050704@domain.hid> Date: Tue, 11 Oct 2005 14:59:20 +0200 From: Philippe Gerum MIME-Version: 1.0 References: <434A585B.40905@domain.hid> <434A601C.7000605@domain.hid> <434B6DA2.6080806@domain.hid> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Xenomai-core] Re: [syscall.c] rt_bind_queue/heap() List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dmitry Adamushko Cc: xenomai@xenomai.org Dmitry Adamushko wrote: > On 11/10/05, Philippe Gerum wrote: > >>>... >>>So, >>> >>>1) don't display such names in /proc; >>>2) make a common mechanism for both spaces. >>> >>>rt_mutex_create() // for other objects as well >>>{ >>>... >>>- xnobject_copy_name(mutex->name,name); >>>+xnobject_create_name(mutex->name,name, object); >>>... >>>} >>> >>>xnobject_create_name(dst,src, object) >>>{ >>> if (src) >>> xnobject_copy_name(mutex->name,name); >>> else >>> snprintf(dst, XNOBJECT_NAME_LEN, "%p", object); >>>} >>> >>>// the slightly ugly thing is that we need to be sure that dst is >>>always object->name so it's really of XNOBJECT_NAME_LEN size. >>> >> >>We should pass the size along with the copy buffer, mainly for readability, and >>also as a safety belt. > > > We don't need that at all, since now we don't want to change a > behaviour of NULL-named objects created from kernel-space. > > > >>>Frankly, I like this approach better. All objects get some name if >>>they are NULL-named by a user and the code changes are a bit more >>>graceful. To show them in /proc or not is still another question. >> >>I'd like we don't generalize an exception case here. The fact that for some >>internal reason we need to put a dummy name on anon objects created from >>user-space should not make all anon objects from kernel space have a registry >>slot too, this would just be overkill (registry slots don't come for free actually). >> >>That said, the remaining point basically is: how do we avoid anon objects with >>auto-generated names from appearing under /proc? I'm not a fan of "magic values" >>which would distinguish a real name from a dummy one, so I'd rather use the >>existing possibility of passing a NULL pnode pointer to rt_registry_enter(), >>which would still index an object without actually exporting it to the /proc >>interface. The question is: how could we make the *_create() calls invoking >>rt_registry_enter() with a NULL pnode when applicable, without changing the >>kernel-based interface of the API. > > > Well, I guess the only way a given *_create() call may determine a > certain environment (kernel mode vs. user mode) is by analyzing some > of the given arguments (ok, in case of the user mode, a previous call > on the stack has been one of the syscall.c:__rt_object_create() ones, > so we may track the stack... ok-ok, I'm just kidding :) > There are only 2 arguments: rt_object *object or char *name. > We probably can't rely on the first one since it may contain anything > and we don't want to force a user to set it up to something certain: > > /* kernel mode */ > RT_MUTEX m; > bzero(&m); // because we use some RT_MUTEX's internal fields when > making a call from syscall.c:__rt_mutex_create(), e.g. m->handle = > DONT_USE_REGISTRY; > > rt_mutex_create(&m, NULL); > > So the only way is to deal somehow with the "name" argument. There is > a difference already. > > rt_mutex_create() being called from: > > 1) kernel mode: name == NULL; > 2) user mode: name == "\0" (see, syscall.c:__rt_mutex_create(), so > *name == NULL; > > Then a fix would look like: > > rt_object_create() > { > ... > > - if (name && *name) > + if (name) > { > + if (*name) > err = rt_registry_enter(mutex->name,mutex,&mutex->handle,&__mutex_pnode); > + else { > + // this is a NULL-named object being created from the user-mode or > + // "\0"-named object from the kernel-mode > +xnobject_create_name(mutex->name, OBJNAME_MAX_SIZE, mutex); > + err = rt_registry_enter(mutex->name,mutex,&mutex->handle,NULL); > +} > > if (err) > rt_mutex_delete(mutex); > } > } > > Maybe a bit ugly but should work. eerrr... I can't come up with a > better solution at the moment. > At least the magic value here would make some sense, NULL=unregistered, empty=registered,not-exported, otherwise=registered,exported. Looks ok for that purpose, since we do need the additional 2nd state here. -- Philippe.