On Wed, 26 Aug 2015 17:22:25 +0530 Pratyush Anand <panand@xxxxxxxxxx> wrote: > Hi Jeff, > > Thanks for your review comments. > > On 26/08/2015:06:31:03 AM, Jeff Layton wrote: > > On Tue, 25 Aug 2015 11:34:19 +0530 > > Pratyush Anand <panand@xxxxxxxxxx> wrote: > > > TP_fast_assign( > > > __entry->xprt = xprt; > > > + __entry->addr = > > > + xprt ? (struct sockaddr *)&xprt->xpt_remote : NULL; > > > > I don't get it. It's not safe to save a pointer to xprt and dereference > > that in a tracepoint (and I understand why that is), but it is safe to > > save a pointer to a structure embedded inside of xprt? Shouldn't you be > > saving a copy of the entire sockaddr struct instead? > > As far as "saving of a pointer to a structure embedded inside of xprt" is > concerned, I do not see any issue. > > Its your take that what you want to print as your tracepoint print output. I > might be missing something.. However, I do not see any value addition in > printing address of a structure(located in ring buffer) where xprt->xpt_remote > has been copied. > > > > > Ahh, ok -- I think I see the confusion. %pIScp does not print the > > address of the sockaddr, but instead dereferences the pointer and > > prints it as a formatted address string. See pointer() in > > lib/vsprintf.c. You do want to save off a copy of the structure instead. > > In my opinion, saving of structure would only be necessary if you want to access > element of the structure xprt->xpt_remote. > > ~Pratyush That's exactly what %pI does. Look at the pointer() function. For this tracepoint, we want to print out the address of the remote end of the socket. That's saved in xprt->xpt_remote. %pIScp doesn't print the pointer's address. It dereferences that pointer and formats and prints the socket address that it points to. If you pass a NULL pointer into anything that uses %pI, it's going to oops. -- Jeff Layton <jlayton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
