IB/mthca: Don't allow userspace open while recovering from catastrophic error

Userspace apps are supposed to release all ib device resources if they
receive a fatal async event (IBV_EVENT_DEVICE_FATAL).  However, the
app has no way of knowing when the device has come back up, except to
repeatedly attempt ibv_open_device() until it succeeds.

However, currently there is no protection against the open succeeding
while the device is in being removed following the fatal event.  In
this case, the open will succeed, but as a result the device waits in
the middle of its removal until the new app releases its resources --
and the new app will not do so, since the open succeeded at a point
following the fatal event generation.

This patch adds an "active" flag to the device. The active flag is set
to false (in the fatal event flow) before the "fatal" event is
generated, so any subsequent ibv_dev_open() call to the device will
fail until the device comes back up, thus preventing the above
deadlock.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_catas.c

@@ -88,6 +88,7 @@ static void handle_catas(struct mthca_dev *dev)
 	event.device = &dev->ib_dev;
 	event.event  = IB_EVENT_DEVICE_FATAL;
 	event.element.port_num = 0;
+	dev->active = false;
 
 	ib_dispatch_event(&event);
 

drivers/infiniband/hw/mthca/mthca_dev.h

@@ -357,6 +357,7 @@ struct mthca_dev {
 	struct ib_ah         *sm_ah[MTHCA_MAX_PORTS];
 	spinlock_t            sm_lock;
 	u8                    rate[MTHCA_MAX_PORTS];
+	bool		      active;
 };
 
 #ifdef CONFIG_INFINIBAND_MTHCA_DEBUG

drivers/infiniband/hw/mthca/mthca_main.c

@@ -1116,6 +1116,8 @@ static int __mthca_init_one(struct pci_dev *pdev, int hca_type)
 	pci_set_drvdata(pdev, mdev);
 	mdev->hca_type = hca_type;
 
+	mdev->active = true;
+
 	return 0;
 
 err_unregister:

drivers/infiniband/hw/mthca/mthca_provider.c

@@ -334,6 +334,9 @@ static struct ib_ucontext *mthca_alloc_ucontext(struct ib_device *ibdev,
 	struct mthca_ucontext           *context;
 	int                              err;
 
+	if (!(to_mdev(ibdev)->active))
+		return ERR_PTR(-EAGAIN);
+
 	memset(&uresp, 0, sizeof uresp);
 
 	uresp.qp_tab_size = to_mdev(ibdev)->limits.num_qps;