On 06/02/17(Mon) 12:27, Martin Pieuchot wrote:
> Paul and Antoine reported that, since the NET_LOCK() went in, doing a
> channel scan with iwm(4) and iwn(4) freezes X.
>
> This is a deadlock due to the fact that wireless drivers sleep during
> a long time holding the NET_LOCK() while the X server tries to
> communicate with unix sockets, that still need the NET_LOCK().
>
> The obvious solution to this problem is to not hold the NET_LOCK() for
> unix socket related operations. We're working on that.
>
> However since hardware ioctl(2) can sleep there's no problem to release
> the NET_LOCK() there. This is true for all ioctls that are not
> modifying any stack state (address, multicast group, etc). Hence the
> diff below that should fix the problem in a generic way.
tb@ found that another code path needs to be unlocked. Diff below does
that. These ioctl(2)s are only messing at the driver level, so it is
safe to drop the NET_LOCK() there as well.
ok?
Index: netinet/in.c
===================================================================
RCS file: /cvs/src/sys/netinet/in.c,v
retrieving revision 1.133
diff -u -p -r1.133 in.c
--- netinet/in.c 20 Dec 2016 12:35:38 -0000 1.133
+++ netinet/in.c 6 Feb 2017 13:43:06 -0000
@@ -390,7 +390,11 @@ in_ioctl(u_long cmd, caddr_t data, struc
default:
if (ifp->if_ioctl == NULL)
return (EOPNOTSUPP);
- return ((*ifp->if_ioctl)(ifp, cmd, data));
+ /* XXXSMP breaks atomicity */
+ rw_exit_write(&netlock);
+ error = ((*ifp->if_ioctl)(ifp, cmd, data));
+ rw_enter_write(&netlock);
+ return (error);
}
return (0);
}
Index: netinet6/in6.c
===================================================================
RCS file: /cvs/src/sys/netinet6/in6.c,v
retrieving revision 1.197
diff -u -p -r1.197 in6.c
--- netinet6/in6.c 5 Feb 2017 16:04:14 -0000 1.197
+++ netinet6/in6.c 6 Feb 2017 13:43:06 -0000
@@ -190,6 +190,7 @@ in6_ioctl(u_long cmd, caddr_t data, stru
struct in6_ifaddr *ia6 = NULL;
struct in6_aliasreq *ifra = (struct in6_aliasreq *)data;
struct sockaddr_in6 *sa6;
+ int error;
if (ifp == NULL)
return (EOPNOTSUPP);
@@ -469,9 +470,13 @@ in6_ioctl(u_long cmd, caddr_t data, stru
break;
default:
- if (ifp == NULL || ifp->if_ioctl == 0)
+ if (ifp->if_ioctl == NULL)
return (EOPNOTSUPP);
- return ((*ifp->if_ioctl)(ifp, cmd, data));
+ /* XXXSMP breaks atomicity */
+ rw_exit_write(&netlock);
+ error = ((*ifp->if_ioctl)(ifp, cmd, data));
+ rw_enter_write(&netlock);
+ return (error);
}
return (0);
Index: dev/pci/if_iwm.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/if_iwm.c,v
retrieving revision 1.162
diff -u -p -r1.162 if_iwm.c
--- dev/pci/if_iwm.c 4 Feb 2017 19:20:59 -0000 1.162
+++ dev/pci/if_iwm.c 6 Feb 2017 14:52:24 -0000
@@ -6133,18 +6133,13 @@ iwm_ioctl(struct ifnet *ifp, u_long cmd,
struct ifreq *ifr;
int s, err = 0;
- /* XXXSMP breaks atomicity */
- rw_exit_write(&netlock);
-
/*
* Prevent processes from entering this function while another
* process is tsleep'ing in it.
*/
err = rw_enter(&sc->ioctl_rwl, RW_WRITE | RW_INTR);
- if (err) {
- rw_enter_write(&netlock);
+ if (err)
return err;
- }
s = splnet();
@@ -6190,7 +6185,6 @@ iwm_ioctl(struct ifnet *ifp, u_long cmd,
splx(s);
rw_exit(&sc->ioctl_rwl);
- rw_enter_write(&netlock);
return err;
}
Index: net/if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.485
diff -u -p -r1.485 if.c
--- net/if.c 1 Feb 2017 02:02:01 -0000 1.485
+++ net/if.c 6 Feb 2017 14:27:47 -0000
@@ -2029,7 +2029,10 @@ ifioctl(struct socket *so, u_long cmd, c
case SIOCGIFPARENT:
if (ifp->if_ioctl == 0)
return (EOPNOTSUPP);
+ /* XXXSMP breaks atomicity */
+ rw_exit_write(&netlock);
error = (*ifp->if_ioctl)(ifp, cmd, data);
+ rw_enter_write(&netlock);
break;
case SIOCGIFDESCR:
