wimax/i2400m: fix deadlock: don't do BUS reset under i2400m->init_mutex

Since the addition of the pre/post reset handlers, it became clear
that we cannot do a I2400M-RT-BUS type reset while holding the
init_mutex, as in the case of USB, it will deadlock when trying to
call i2400m_pre_reset().

Thus, the following changes:

 - clarify the fact that calling bus_reset() w/ I2400M_RT_BUS while
   holding init_mutex is a no-no.

 - i2400m_dev_reset_handle() will do a BUS reset to recover a gone
   device after unlocking init_mutex.

 - in the USB reset implementation, when cold and warm reset fails,
   fallback to QUEUING a usb reset, not executing a USB reset, so it
   happens from another context and does not deadlock.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/net/wimax/i2400m/usb.c b/drivers/net/wimax/i2400m/usb.c
index 8b246cc498b1..418db12b0cd7 100644
--- a/drivers/net/wimax/i2400m/usb.c
+++ b/drivers/net/wimax/i2400m/usb.c
@@ -254,7 +254,6 @@ int i2400mu_bus_reset(struct i2400m *i2400m, enum i2400m_reset_type rt)
                         sizeof(i2400m_COLD_BOOT_BARKER),
                         i2400mu->endpoint_cfg.reset_cold);
         else if (rt == I2400M_RT_BUS) {
-do_bus_reset:
                 result = usb_reset_device(i2400mu->usb_dev);
                 switch (result) {
                 case 0:
@@ -262,7 +261,7 @@ do_bus_reset:
                 case -ENODEV:
                 case -ENOENT:
                 case -ESHUTDOWN:
-                        result = rt == I2400M_RT_WARM ? -ENODEV : 0;
+                        result = 0;
                         break;  /* We assume the device is disconnected */
                 default:
                         dev_err(dev, "USB reset failed (%d), giving up!\n",
@@ -275,10 +274,17 @@ do_bus_reset:
         if (result < 0
             && result != -EINVAL        /* device is gone */
             && rt != I2400M_RT_BUS) {
+                /*
+                 * Things failed -- resort to lower level reset, that
+                 * we queue in another context; the reason for this is
+                 * that the pre and post reset functionality requires
+                 * the i2400m->init_mutex; RT_WARM and RT_COLD can
+                 * come from areas where i2400m->init_mutex is taken.
+                 */
                 dev_err(dev, "%s reset failed (%d); trying USB reset\n",
                         rt == I2400M_RT_WARM ? "warm" : "cold", result);
-                rt = I2400M_RT_BUS;
-                goto do_bus_reset;
+                usb_queue_reset_device(i2400mu->usb_iface);
+                result = -ENODEV;
         }
         d_fnend(3, dev, "(i2400m %p rt %u) = %d\n", i2400m, rt, result);
         return result;