wimax/i2400m: clarify and fix i2400m->{ready,updown}

The i2400m driver uses two different bits to distinguish how much the
driver is up. i2400m->ready is used to denote that the infrastructure
to communicate with the device is up and running. i2400m->updown is
used to indicate if 'ready' and the device is up and running, ready to
take control and data traffic.

However, all this was pretty dirty and not clear, with many open spots
where race conditions were present.

This commit cleans up the situation by:

 - documenting the usage of both bits

 - setting them only in specific, well controlled places
   (i2400m_dev_start, i2400m_dev_stop)

 - ensuring the i2400m workqueue can't get in the middle of the
   setting by flushing it when i2400m->ready is set to zero. This
   allows the report hook not having to check again for the bit to be
   set [rx.c:i2400m_report_hook_work()].

 - using i2400m->updown to determine if the device is up and running
   instead of the wimax state in i2400m_dev_reset_handle().

 - not loosing missed messages sent by the hardware before
   i2400m->ready is set. In rx.c, whatever the device sends can be
   sent to user space over the message pipes as soon as the wimax
   device is registered, so don't wait for i2400m->ready to be set.

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

1 files changed, 29 insertions, 15 deletions

diff --git a/drivers/net/wimax/i2400m/driver.c b/drivers/net/wimax/i2400m/driver.c
index a0ae19966c0c..6280646d7d7f 100644
--- a/drivers/net/wimax/i2400m/driver.c
+++ b/drivers/net/wimax/i2400m/driver.c
@@ -455,6 +455,8 @@ retry:
         result = i2400m->bus_dev_start(i2400m);
         if (result < 0)
                 goto error_bus_dev_start;
+        i2400m->ready = 1;
+        wmb();          /* see i2400m->ready's documentation  */
         result = i2400m_firmware_check(i2400m); /* fw versions ok? */
         if (result < 0)
                 goto error_fw_check;
@@ -462,7 +464,6 @@ retry:
         result = i2400m_check_mac_addr(i2400m);
         if (result < 0)
                 goto error_check_mac_addr;
-        i2400m->ready = 1;
         wimax_state_change(wimax_dev, WIMAX_ST_UNINITIALIZED);
         result = i2400m_dev_initialize(i2400m);
         if (result < 0)
@@ -475,6 +476,9 @@ retry:
 
 error_dev_initialize:
 error_check_mac_addr:
+        i2400m->ready = 0;
+        wmb();          /* see i2400m->ready's documentation  */
+        flush_workqueue(i2400m->work_queue);
 error_fw_check:
         i2400m->bus_dev_stop(i2400m);
 error_bus_dev_start:
@@ -498,11 +502,15 @@ error_bootstrap:
 static
 int i2400m_dev_start(struct i2400m *i2400m, enum i2400m_bri bm_flags)
 {
-        int result;
+        int result = 0;
         mutex_lock(&i2400m->init_mutex);        /* Well, start the device */
-        result = __i2400m_dev_start(i2400m, bm_flags);
-        if (result >= 0)
-                i2400m->updown = 1;
+        if (i2400m->updown == 0) {
+                result = __i2400m_dev_start(i2400m, bm_flags);
+                if (result >= 0) {
+                        i2400m->updown = 1;
+                        wmb();  /* see i2400m->updown's documentation */
+                }
+        }
         mutex_unlock(&i2400m->init_mutex);
         return result;
 }
@@ -529,7 +537,14 @@ void __i2400m_dev_stop(struct i2400m *i2400m)
         wimax_state_change(wimax_dev, __WIMAX_ST_QUIESCING);
         i2400m_net_wake_stop(i2400m);
         i2400m_dev_shutdown(i2400m);
-        i2400m->ready = 0;
+        /*
+         * Make sure no report hooks are running *before* we stop the
+         * communication infrastructure with the device.
+         */
+        i2400m->ready = 0;      /* nobody can queue work anymore */
+        wmb();          /* see i2400m->ready's documentation  */
+        flush_workqueue(i2400m->work_queue);
+
         i2400m->bus_dev_stop(i2400m);
         destroy_workqueue(i2400m->work_queue);
         i2400m_rx_release(i2400m);
@@ -551,6 +566,7 @@ void i2400m_dev_stop(struct i2400m *i2400m)
         if (i2400m->updown) {
                 __i2400m_dev_stop(i2400m);
                 i2400m->updown = 0;
+                wmb();  /* see i2400m->updown's documentation  */
         }
         mutex_unlock(&i2400m->init_mutex);
 }
@@ -632,7 +648,6 @@ void __i2400m_dev_reset_handle(struct work_struct *ws)
         const char *reason;
         struct i2400m *i2400m = iw->i2400m;
         struct device *dev = i2400m_dev(i2400m);
-        enum wimax_st wimax_state;
         struct i2400m_reset_ctx *ctx = i2400m->reset_ctx;
 
         if (WARN_ON(iw->pl_size != sizeof(reason)))
@@ -647,29 +662,28 @@ void __i2400m_dev_reset_handle(struct work_struct *ws)
                 /* We are still in i2400m_dev_start() [let it fail] or
                  * i2400m_dev_stop() [we are shutting down anyway, so
                  * ignore it] or we are resetting somewhere else. */
-                dev_err(dev, "device rebooted\n");
+                dev_err(dev, "device rebooted somewhere else?\n");
                 i2400m_msg_to_dev_cancel_wait(i2400m, -EL3RST);
                 complete(&i2400m->msg_completion);
                 goto out;
         }
-        wimax_state = wimax_state_get(&i2400m->wimax_dev);
-        if (wimax_state < WIMAX_ST_UNINITIALIZED) {
-                dev_info(dev, "%s: it is down, ignoring\n", reason);
-                goto out_unlock;        /* ifconfig up/down wasn't called */
+        if (i2400m->updown == 0)  {
+                dev_info(dev, "%s: device is down, doing nothing\n", reason);
+                goto out_unlock;
         }
         dev_err(dev, "%s: reinitializing driver\n", reason);
         __i2400m_dev_stop(i2400m);
-        i2400m->updown = 0;
         result = __i2400m_dev_start(i2400m,
                                     I2400M_BRI_SOFT | I2400M_BRI_MAC_REINIT);
         if (result < 0) {
+                i2400m->updown = 0;
+                wmb();          /* see i2400m->updown's documentation  */
                 dev_err(dev, "%s: cannot start the device: %d\n",
                         reason, result);
                 result = i2400m->bus_reset(i2400m, I2400M_RT_BUS);
                 if (result >= 0)
                         result = -ENODEV;
-        } else
-                i2400m->updown = 1;
+        }
 out_unlock:
         if (i2400m->reset_ctx) {
                 ctx->result = result;