On Fri, May 30, 2014 at 10:58:11AM -0700, Michael Chan wrote: > On Fri, 2014-05-30 at 11:00 -0400, Neil Horman wrote: > > The Cnic driver handles lots of ulp operations in its netdevice event hanlder. > > To do this, it accesses the ulp_ops array, which is an rcu protected array. > > However, some ulp operations (like bnx2fc_indicate_netevent) try to lock > > mutexes, which might sleep (somthing that you can't do while holding rcu read > > side locks if you've configured non-preemptive rcu. > > > > Fix this by changing the dereference method. All accesses to the ulp_ops array > > for a cnic dev are modified under the protection of the rtnl lock, and so we can > > safely just use rcu_dereference_rtnl, and remove the rcu_read_lock here > > Because the bnx2fc function can sleep, we need a more complete fix to > prevent the ulp_ops from going away when the device is unregistered. > synchronize_rcu() won't be able to protect it. I'll post the patch > later today. Thanks. > The device can't be unregistered while we hold rtnl, can it? Since we hold it in this path it seems safe to me, even if we sleep, or am I missing something? Neil > > > > Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx> > > CC: "David S. Miller" <davem@xxxxxxxxxxxxx> > > CC: Michael Chan <mchan@xxxxxxxxxxxx> > > CC: fcoe-devel@xxxxxxxxxxxxx > > CC: Robert Love <robert.w.love@xxxxxxxxx> > > CC: Vasu Dev <vasu.dev@xxxxxxxxx> > > --- > > drivers/net/ethernet/broadcom/cnic.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/drivers/net/ethernet/broadcom/cnic.c b/drivers/net/ethernet/broadcom/cnic.c > > index f58a8b8..bfdb9f0 100644 > > --- a/drivers/net/ethernet/broadcom/cnic.c > > +++ b/drivers/net/ethernet/broadcom/cnic.c > > @@ -5622,12 +5622,11 @@ static void cnic_rcv_netevent(struct cnic_local *cp, unsigned long event, > > { > > int if_type; > > > > - rcu_read_lock(); > > for (if_type = 0; if_type < MAX_CNIC_ULP_TYPE; if_type++) { > > struct cnic_ulp_ops *ulp_ops; > > void *ctx; > > > > - ulp_ops = rcu_dereference(cp->ulp_ops[if_type]); > > + ulp_ops = rcu_dereference_rtnl(cp->ulp_ops[if_type]); > > if (!ulp_ops || !ulp_ops->indicate_netevent) > > continue; > > > > @@ -5635,7 +5634,6 @@ static void cnic_rcv_netevent(struct cnic_local *cp, unsigned long event, > > > > ulp_ops->indicate_netevent(ctx, event, vlan_id); > > } > > - rcu_read_unlock(); > > } > > > > /* netdev event handler */ > > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html