usb: xhci: dbc: Fix lockdep warning

The xHCI DbC implementation might enter a deadlock situation because
there is no sufficient protection against the shared data between
process and softirq contexts. This can lead to the following lockdep
warnings. This patch changes to use spin_{,un}lock_irq{save,restore}
to avoid potential deadlock.

[ 528.248084] ================================
[ 528.252914] WARNING: inconsistent lock state
[ 528.257756] 4.15.0-rc1+ #1630 Not tainted
[ 528.262305] --------------------------------
[ 528.267145] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 528.273953] ksoftirqd/1/17 [HC0[0]:SC1[1]:HE0:SE0] takes:
[ 528.280075] (&(&port->port_lock)->rlock){+.?.}, at: [<ffffffff815396a8>] dbc_rx_push+0x38/0x1c0
[ 528.290043] {SOFTIRQ-ON-W} state was registered at:
[ 528.295570] _raw_spin_lock+0x2f/0x40
[ 528.299818] dbc_write_complete+0x27/0xa0
[ 528.304458] xhci_dbc_giveback+0xd1/0x200
[ 528.309098] xhci_dbc_flush_endpoint_requests+0x50/0x70
[ 528.315116] xhci_dbc_handle_events+0x696/0x7b0
[ 528.320349] process_one_work+0x1ee/0x6e0
[ 528.324988] worker_thread+0x4a/0x430
[ 528.329236] kthread+0x13e/0x170
[ 528.332992] ret_from_fork+0x24/0x30
[ 528.337141] irq event stamp: 2861
[ 528.340897] hardirqs last enabled at (2860): [<ffffffff810674ea>] tasklet_action+0x6a/0x250
[ 528.350460] hardirqs last disabled at (2861): [<ffffffff817dc1ef>] _raw_spin_lock_irq+0xf/0x40
[ 528.360219] softirqs last enabled at (2852): [<ffffffff817e0e8c>] __do_softirq+0x3dc/0x4f9
[ 528.369683] softirqs last disabled at (2857): [<ffffffff8106805b>] run_ksoftirqd+0x1b/0x60
[ 528.379048]
[ 528.379048] other info that might help us debug this:
[ 528.386443] Possible unsafe locking scenario:
[ 528.386443]
[ 528.393150] CPU0
[ 528.395917] ----
[ 528.398687] lock(&(&port->port_lock)->rlock);
[ 528.403821] <Interrupt>
[ 528.406786] lock(&(&port->port_lock)->rlock);
[ 528.412116]
[ 528.412116] *** DEADLOCK ***
[ 528.412116]
[ 528.418825] no locks held by ksoftirqd/1/17.
[ 528.423662]
[ 528.423662] stack backtrace:
[ 528.428598] CPU: 1 PID: 17 Comm: ksoftirqd/1 Not tainted 4.15.0-rc1+ #1630
[ 528.436387] Call Trace:
[ 528.439158] dump_stack+0x5e/0x8e
[ 528.442914] print_usage_bug+0x1fc/0x220
[ 528.447357] mark_lock+0x4db/0x5a0
[ 528.451210] __lock_acquire+0x726/0x1130
[ 528.455655] ? __lock_acquire+0x557/0x1130
[ 528.460296] lock_acquire+0xa2/0x200
[ 528.464347] ? dbc_rx_push+0x38/0x1c0
[ 528.468496] _raw_spin_lock_irq+0x35/0x40
[ 528.473038] ? dbc_rx_push+0x38/0x1c0
[ 528.477186] dbc_rx_push+0x38/0x1c0
[ 528.481139] tasklet_action+0x1d2/0x250
[ 528.485483] __do_softirq+0x1dc/0x4f9
[ 528.489630] run_ksoftirqd+0x1b/0x60
[ 528.493682] smpboot_thread_fn+0x179/0x270
[ 528.498324] kthread+0x13e/0x170
[ 528.501981] ? sort_range+0x20/0x20
[ 528.505933] ? kthread_delayed_work_timer_fn+0x80/0x80
[ 528.511755] ret_from_fork+0x24/0x30

Fixes: dfba2174 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-dbgcap.c

@@ -328,13 +328,14 @@ dbc_ep_do_queue(struct dbc_ep *dep, struct dbc_request *req)
 int dbc_ep_queue(struct dbc_ep *dep, struct dbc_request *req,
 		 gfp_t gfp_flags)
 {
+	unsigned long		flags;
 	struct xhci_dbc		*dbc = dep->dbc;
 	int			ret = -ESHUTDOWN;
 
-	spin_lock(&dbc->lock);
+	spin_lock_irqsave(&dbc->lock, flags);
 	if (dbc->state == DS_CONFIGURED)
 		ret = dbc_ep_do_queue(dep, req);
-	spin_unlock(&dbc->lock);
+	spin_unlock_irqrestore(&dbc->lock, flags);
 
 	mod_delayed_work(system_wq, &dbc->event_work, 0);
 
@@ -521,15 +522,16 @@ static void xhci_do_dbc_stop(struct xhci_hcd *xhci)
 static int xhci_dbc_start(struct xhci_hcd *xhci)
 {
 	int			ret;
+	unsigned long		flags;
 	struct xhci_dbc		*dbc = xhci->dbc;
 
 	WARN_ON(!dbc);
 
 	pm_runtime_get_sync(xhci_to_hcd(xhci)->self.controller);
 
-	spin_lock(&dbc->lock);
+	spin_lock_irqsave(&dbc->lock, flags);
 	ret = xhci_do_dbc_start(xhci);
-	spin_unlock(&dbc->lock);
+	spin_unlock_irqrestore(&dbc->lock, flags);
 
 	if (ret) {
 		pm_runtime_put(xhci_to_hcd(xhci)->self.controller);
@@ -541,6 +543,7 @@ static int xhci_dbc_start(struct xhci_hcd *xhci)
 
 static void xhci_dbc_stop(struct xhci_hcd *xhci)
 {
+	unsigned long		flags;
 	struct xhci_dbc		*dbc = xhci->dbc;
 	struct dbc_port		*port = &dbc->port;
 
@@ -551,9 +554,9 @@ static void xhci_dbc_stop(struct xhci_hcd *xhci)
 	if (port->registered)
 		xhci_dbc_tty_unregister_device(xhci);
 
-	spin_lock(&dbc->lock);
+	spin_lock_irqsave(&dbc->lock, flags);
 	xhci_do_dbc_stop(xhci);
-	spin_unlock(&dbc->lock);
+	spin_unlock_irqrestore(&dbc->lock, flags);
 
 	pm_runtime_put_sync(xhci_to_hcd(xhci)->self.controller);
 }
@@ -779,14 +782,15 @@ static void xhci_dbc_handle_events(struct work_struct *work)
 	int			ret;
 	enum evtreturn		evtr;
 	struct xhci_dbc		*dbc;
+	unsigned long		flags;
 	struct xhci_hcd		*xhci;
 
 	dbc = container_of(to_delayed_work(work), struct xhci_dbc, event_work);
 	xhci = dbc->xhci;
 
-	spin_lock(&dbc->lock);
+	spin_lock_irqsave(&dbc->lock, flags);
 	evtr = xhci_dbc_do_handle_events(dbc);
-	spin_unlock(&dbc->lock);
+	spin_unlock_irqrestore(&dbc->lock, flags);
 
 	switch (evtr) {
 	case EVT_GSER:

drivers/usb/host/xhci-dbgtty.c

@@ -92,21 +92,23 @@ static void dbc_start_rx(struct dbc_port *port)
 static void
 dbc_read_complete(struct xhci_hcd *xhci, struct dbc_request *req)
 {
+	unsigned long		flags;
 	struct xhci_dbc		*dbc = xhci->dbc;
 	struct dbc_port		*port = &dbc->port;
 
-	spin_lock(&port->port_lock);
+	spin_lock_irqsave(&port->port_lock, flags);
 	list_add_tail(&req->list_pool, &port->read_queue);
 	tasklet_schedule(&port->push);
-	spin_unlock(&port->port_lock);
+	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
 static void dbc_write_complete(struct xhci_hcd *xhci, struct dbc_request *req)
 {
+	unsigned long		flags;
 	struct xhci_dbc		*dbc = xhci->dbc;
 	struct dbc_port		*port = &dbc->port;
 
-	spin_lock(&port->port_lock);
+	spin_lock_irqsave(&port->port_lock, flags);
 	list_add(&req->list_pool, &port->write_pool);
 	switch (req->status) {
 	case 0:
@@ -119,7 +121,7 @@ static void dbc_write_complete(struct xhci_hcd *xhci, struct dbc_request *req)
 			  req->status);
 		break;
 	}
-	spin_unlock(&port->port_lock);
+	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
 static void xhci_dbc_free_req(struct dbc_ep *dep, struct dbc_request *req)
@@ -327,12 +329,13 @@ static void dbc_rx_push(unsigned long _port)
 {
 	struct dbc_request	*req;
 	struct tty_struct	*tty;
+	unsigned long		flags;
 	bool			do_push = false;
 	bool			disconnect = false;
 	struct dbc_port		*port = (void *)_port;
 	struct list_head	*queue = &port->read_queue;
 
-	spin_lock_irq(&port->port_lock);
+	spin_lock_irqsave(&port->port_lock, flags);
 	tty = port->port.tty;
 	while (!list_empty(queue)) {
 		req = list_first_entry(queue, struct dbc_request, list_pool);
@@ -392,16 +395,17 @@ static void dbc_rx_push(unsigned long _port)
 	if (!disconnect)
 		dbc_start_rx(port);
 
-	spin_unlock_irq(&port->port_lock);
+	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
 static int dbc_port_activate(struct tty_port *_port, struct tty_struct *tty)
 {
+	unsigned long	flags;
 	struct dbc_port	*port = container_of(_port, struct dbc_port, port);
 
-	spin_lock_irq(&port->port_lock);
+	spin_lock_irqsave(&port->port_lock, flags);
 	dbc_start_rx(port);
-	spin_unlock_irq(&port->port_lock);
+	spin_unlock_irqrestore(&port->port_lock, flags);
 
 	return 0;
 }