Package: hurd
Version: n/a
Hi,
Neal reported this bug to me a while ago. If you send an invalid message (a
message with an unhandled msgid) to a pager, it will miss out on this msg id
and the seqno stuff doesn't catch up anymore. The result is a deadlock
waiting for this msg id when the next valid message is processed.
Neal and me agreed on a potential fix for this, the patch is below. The
only thing I am uncertain about is what checks need to be done on the msg
format. Does the kernel guarantee that the header up to msgh_remote_port
really exists and is valid? I'd guess so much, but I didn't verify it.
2001-01-16 Marcus Brinkmann <[EMAIL PROTECTED]>
* demuxer.c (pager_demuxer): If the message was not accepted by one
of the servers, acquire a reference to the pager and its lock, and
wait until all previous messages have been processed. This makes
sure that the next message that arrives can proceed.
Reported by Neal H Walfield <[EMAIL PROTECTED]>
Index: demuxer.c
===================================================================
RCS file: /cvsroot/hurd/hurd/libpager/demuxer.c,v
retrieving revision 1.8
diff -u -p -r1.8 demuxer.c
--- demuxer.c 20 Jun 1995 16:56:05 -0000 1.8
+++ demuxer.c 16 Jan 2002 19:17:12 -0000
@@ -20,7 +20,7 @@
#include "notify_S.h"
/* Demultiplex a single message directed at a pager port; INP is the
- message received; fille OUTP with the reply. */
+ message received; fill OUTP with the reply. */
int
pager_demuxer (mach_msg_header_t *inp,
mach_msg_header_t *outp)
@@ -30,7 +30,24 @@ pager_demuxer (mach_msg_header_t *inp,
extern int _pager_seqnos_notify_server (mach_msg_header_t *inp,
mach_msg_header_t *outp);
- return (_pager_seqnos_memory_object_server (inp, outp)
- || _pager_seqnos_notify_server (inp, outp));
+ int result = _pager_seqnos_memory_object_server (inp, outp)
+ || _pager_seqnos_notify_server (inp, outp);
+ if (!result)
+ {
+ struct pager *p;
+
+ p = ports_lookup_port (0, inp->msgh_remote_port, _pager_class);
+ if (p)
+ {
+ mutex_lock (&p->interlock);
+ _pager_wait_for_seqno (p, seqno);
+ _pager_release_seqno (p, seqno);
+ mutex_unlock (&p->interlock);
+ ports_port_deref (p);
+ }
+ }
+ return result;
}
+
+
--
`Rhubarb is no Egyptian god.' Debian http://www.debian.org [EMAIL PROTECTED]
Marcus Brinkmann GNU http://www.gnu.org [EMAIL PROTECTED]
[EMAIL PROTECTED]
http://www.marcus-brinkmann.de
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