Re: mountd segfault on itanium2

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, May 03, 2004 at 05:17:18PM -0700, Garrick Staples wrote:
> I'm slowly starting to wrap my brain around how these RPC calls work.  I've
> found something that I can't make sense of.  In my_svc_run(), it packs fds 3,
> 4, 5, 6, and 7 into select().  3, 4, and 5 are 3 files in /proc/net/rpc.  fd 6
>  and 7 are udp and tcp sockets.  During my umount/mount tests, fd 6 is the
> only set bit after the select(), and is then passed to svc_getreqset().
> 
> But just before the segfault, select() sets fd 5, which is
> /proc/net/rpc/nfsd.fh/channel.  The thing that I don't understand is that fd 5
> is being passed to svc_getreqset().  Shouldn't svc_getreqset() be only for fds
> of sockets that have pending rpc calls?  Should fd 5 be cleared from the fdset
> before calling svc_getreqset()?

Cool, good detective work, I think that must be it.  Other people
weren't seeing it because you have to be using the new interface (have
nfsd mounted), and have to get an rpc call and a kernel upcall at the
same time.  Does clearing the bit end the segfaults?

--Bruce Fields

>From Garrick Staples <garrick@usc.edu>:

After mountd handles a cache upcall, we should clear the relevant bits in the
fd_set.


 utils/mountd/cache.c |    1 +
 1 files changed, 1 insertion(+)

diff -puN utils/mountd/svc_run.c~cache_select_bugfix utils/mountd/svc_run.c
diff -puN utils/mountd/cache.c~cache_select_bugfix utils/mountd/cache.c
--- nfs-utils-1.0.6/utils/mountd/cache.c~cache_select_bugfix	2004-05-03 20:57:15.000000000 -0400
+++ nfs-utils-1.0.6-bfields/utils/mountd/cache.c	2004-05-03 20:57:15.000000000 -0400
@@ -315,6 +315,7 @@ int cache_process_req(fd_set *readfds) 
 		    FD_ISSET(fileno(cachelist[i].f), readfds)) {
 			cnt++;
 			cachelist[i].cache_handle(cachelist[i].f);
+			FD_CLR(fileno(cachelist[i].f), readfds);
 		}
 	}
 	return cnt;

_


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