Module Name: src
Committed By: msaitoh
Date: Fri Nov 30 06:30:39 UTC 2012
Modified Files:
src/sys/arch/xen/xenbus [netbsd-6-0]: xenbus_xs.c
Log Message:
Pull up following revision(s) (requested by royger in ticket #728):
sys/arch/xen/xenbus/xenbus_xs.c: revision 1.23
xen: prevent adding duplicate xenwatches
When a xenstore watch triggers, the event is processed on process_msg
and if a valid handle it's found the handler is queued for execution
on the pending xen watches queue (watch_events).
This may present a problem if we trigger a xenwatch several times and
then disconnect the device. If several xenwatch events are added to
the watch_events queue and the device is disconnected afterwards, the
first processed xenwatch event will disconnect the device, remove the
watch and free all resources. This triggers a panic if there are
pending xenwatch events for that device already queued in the local
queue of the function xenwatch_thread, since when the next watch that
has the same handler tries to execute we get a panic due to the fact
that the device is already disconnected and all resources had been
freed:
xenbus_watch: 0xffffa0000b7cd1d0
xbw_callback: 0xffffffff80755dd4
otherend_changed: backend/vif/1/0
backend/vif/1/0/state 6
backend/vif/1/0 -> Closed
backend/vif/1/0 -> backend_device, b_detach: 0xffffffff8075a2bf
xenbus_watch: 0xffffa0000b7cd1d0
xbw_callback: 0xfc5ec02183e547a8
fatal protection fault in supervisor mode
trap type 4 code 0 rip ffffffff80756596 cs e030 rflags 10246 cr2
7f7ff7b4c020 ilevel 0 rsp ffffa000e6d82c50
curlwp 0xffffa0000a72d580 pid 0 lid 36 lowest kstack
0xffffa000e6d7f000
kernel: protection fault trap, code=0
Stopped in pid 0.36 (system) at netbsd:xenwatch_thread+0xc7: call
*10(%rax
)
xenwatch_thread() at netbsd:xenwatch_thread+0xc7
ds f
es 5987
fs 2c40
gs 1460
rdi ffffa0000b7cd1d0
rsi ffffa0000a5477f0
rbp ffffa000e6d82c70
rbx ffffa0000b7c14c0
rdx 2
rcx f
rax ffffa0000b7cd1d0
r8 78
r9 ffffffef
r10 deadbeef
r11 1
r12 ffffa000e6d82c50
r13 ffffa0000a72d580
r14 ffffa0000a72d580
r15 0
rip ffffffff80756596 xenwatch_thread+0xc7
cs e030
rflags 10246
rsp ffffa000e6d82c50
ss e02b
netbsd:xenwatch_thread+0xc7: call *10(%rax)
To generate a diff of this commit:
cvs rdiff -u -r1.22 -r1.22.14.1 src/sys/arch/xen/xenbus/xenbus_xs.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/xen/xenbus/xenbus_xs.c
diff -u src/sys/arch/xen/xenbus/xenbus_xs.c:1.22 src/sys/arch/xen/xenbus/xenbus_xs.c:1.22.14.1
--- src/sys/arch/xen/xenbus/xenbus_xs.c:1.22 Wed Jul 27 23:11:23 2011
+++ src/sys/arch/xen/xenbus/xenbus_xs.c Fri Nov 30 06:30:38 2012
@@ -1,4 +1,4 @@
-/* $NetBSD: xenbus_xs.c,v 1.22 2011/07/27 23:11:23 matt Exp $ */
+/* $NetBSD: xenbus_xs.c,v 1.22.14.1 2012/11/30 06:30:38 msaitoh Exp $ */
/******************************************************************************
* xenbus_xs.c
*
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xenbus_xs.c,v 1.22 2011/07/27 23:11:23 matt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xenbus_xs.c,v 1.22.14.1 2012/11/30 06:30:38 msaitoh Exp $");
#if 0
#define DPRINTK(fmt, args...) \
@@ -751,7 +751,7 @@ xenwatch_thread(void *unused)
static int
process_msg(void)
{
- struct xs_stored_msg *msg;
+ struct xs_stored_msg *msg, *s_msg;
char *body;
int err;
@@ -782,7 +782,7 @@ process_msg(void)
body[msg->hdr.len] = '\0';
if (msg->hdr.type == XS_WATCH_EVENT) {
- bool found;
+ bool found, repeated;
DPRINTK("process_msg: XS_WATCH_EVENT");
msg->u.watch.vec = split(body, msg->hdr.len,
@@ -796,14 +796,24 @@ process_msg(void)
msg->u.watch.handle = find_watch(
msg->u.watch.vec[XS_WATCH_TOKEN]);
found = (msg->u.watch.handle != NULL);
+ repeated = false;
if (found) {
mutex_enter(&watch_events_lock);
- SIMPLEQ_INSERT_TAIL(&watch_events, msg, msg_next);
- cv_broadcast(&watch_cv);
+ /* Don't add duplicate events to the queue of pending watches */
+ SIMPLEQ_FOREACH(s_msg, &watch_events, msg_next) {
+ if (s_msg->u.watch.handle == msg->u.watch.handle) {
+ repeated = true;
+ break;
+ }
+ }
+ if (!repeated) {
+ SIMPLEQ_INSERT_TAIL(&watch_events, msg, msg_next);
+ cv_broadcast(&watch_cv);
+ }
mutex_exit(&watch_events_lock);
}
mutex_exit(&watches_lock);
- if (!found) {
+ if (!found || repeated) {
free(msg->u.watch.vec, M_DEVBUF);
free(msg, M_DEVBUF);
}
