[PATCH 4.9 16/16] usb: musb: fix possible spinlock deadlock

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bin Liu <b-liu@xxxxxx>

commit bc1e2154542071e3cfe1734b143af9b8bdacf8bd upstream.

The DSPS glue calls del_timer_sync() in its musb_platform_disable()
implementation, which requires the caller to not hold a lock. But
musb_remove() calls musb_platform_disable() will musb->lock held. This
could causes spinlock deadlock.

So change musb_remove() to call musb_platform_disable() without holds
musb->lock. This doesn't impact the musb_platform_disable implementation
in other glue drivers.

root@am335x-evm:~# modprobe -r musb-dsps
[  126.134879] musb-hdrc musb-hdrc.1: remove, state 1
[  126.140465] usb usb2: USB disconnect, device number 1
[  126.146178] usb 2-1: USB disconnect, device number 2
[  126.416985] musb-hdrc musb-hdrc.1: USB bus 2 deregistered
[  126.423943]
[  126.425525] ======================================================
[  126.431997] [ INFO: possible circular locking dependency detected ]
[  126.438564] 4.11.0-rc1-00003-g1557f13bca04-dirty #77 Not tainted
[  126.444852] -------------------------------------------------------
[  126.451414] modprobe/778 is trying to acquire lock:
[  126.456523]  (((&glue->timer))){+.-...}, at: [<c01b8788>] del_timer_sync+0x0/0xd0
[  126.464403]
[  126.464403] but task is already holding lock:
[  126.470511]  (&(&musb->lock)->rlock){-.-...}, at: [<bf30b7f8>] musb_remove+0x50/0x1
30 [musb_hdrc]
[  126.479965]
[  126.479965] which lock already depends on the new lock.
[  126.479965]
[  126.488531]
[  126.488531] the existing dependency chain (in reverse order) is:
[  126.496368]
[  126.496368] -> #1 (&(&musb->lock)->rlock){-.-...}:
[  126.502968]        otg_timer+0x80/0xec [musb_dsps]
[  126.507990]        call_timer_fn+0xb4/0x390
[  126.512372]        expire_timers+0xf0/0x1fc
[  126.516754]        run_timer_softirq+0x80/0x178
[  126.521511]        __do_softirq+0xc4/0x554
[  126.525802]        irq_exit+0xe8/0x158
[  126.529735]        __handle_domain_irq+0x58/0xb8
[  126.534583]        __irq_usr+0x54/0x80
[  126.538507]
[  126.538507] -> #0 (((&glue->timer))){+.-...}:
[  126.544636]        del_timer_sync+0x40/0xd0
[  126.549066]        musb_remove+0x6c/0x130 [musb_hdrc]
[  126.554370]        platform_drv_remove+0x24/0x3c
[  126.559206]        device_release_driver_internal+0x14c/0x1e0
[  126.565225]        bus_remove_device+0xd8/0x108
[  126.569970]        device_del+0x1e4/0x308
[  126.574170]        platform_device_del+0x24/0x8c
[  126.579006]        platform_device_unregister+0xc/0x20
[  126.584394]        dsps_remove+0x14/0x30 [musb_dsps]
[  126.589595]        platform_drv_remove+0x24/0x3c
[  126.594432]        device_release_driver_internal+0x14c/0x1e0
[  126.600450]        driver_detach+0x38/0x6c
[  126.604740]        bus_remove_driver+0x4c/0xa0
[  126.609407]        SyS_delete_module+0x11c/0x1e4
[  126.614252]        __sys_trace_return+0x0/0x10

Fixes: ea2f35c01d5ea ("usb: musb: Fix sleeping function called from invalid context for hdrc glue")
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
Signed-off-by: Bin Liu <b-liu@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/musb/musb_core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -2467,8 +2467,8 @@ static int musb_remove(struct platform_d
 	pm_runtime_get_sync(musb->controller);
 	musb_host_cleanup(musb);
 	musb_gadget_cleanup(musb);
-	spin_lock_irqsave(&musb->lock, flags);
 	musb_platform_disable(musb);
+	spin_lock_irqsave(&musb->lock, flags);
 	musb_generic_disable(musb);
 	spin_unlock_irqrestore(&musb->lock, flags);
 	musb_writeb(musb->mregs, MUSB_DEVCTL, 0);