On Mon, 10 Mar 2014 22:41:31 -0400 f...@redhat.com (Frank Ch. Eigler) wrote:
> > Hi - > > > >> From: Steven Rostedt <rost...@goodmis.org> > >> > >> Tracepoints were made to allow enabling a tracepoint in a module before > >> that > >> module was loaded. When a tracepoint is enabled and it does not exist, the > >> name is stored and will be enabled when the tracepoint is created. > >> > >> The problem with this approach is that when a tracepoint is enabled when > >> it expects to be there, it gives no warning that it does not exist. > > So it is a deferred-activation kind of call, with no way of knowing > when or if the tracepoints will start coming in. Why is that > supported at all, considering that clients could monitor modules > coming & going via the module_notifier chain, and update registration > at that time? That's my argument. > > > >> + entry = get_tracepoint(name); > >> + /* Make sure the entry was enabled */ > >> + if (!entry || !entry->enabled) > >> + ret = -ENODEV; > > For what it's worth, I agree with Mathieu that this sort of successful > failure result code is a problem for tracking what needs cleanup and > what doesn't. (In systemtap's case, if this change gets merged, we'll > have to treat -ENODEV as if it were 0.) Does systemtap enable tracepoints before they are created? That is, do you allow enabling of a tracepoint in a module that is not loaded yet? If not, than you want this as an error. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
