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Commit b9ee9501 authored by Inaky Perez-Gonzalez's avatar Inaky Perez-Gonzalez
Browse files

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: default avatarInaky Perez-Gonzalez <inaky@linux.intel.com>
parent 5eeae35b

drivers/net/wimax/i2400m/driver.c

+7 −3
Original line number Diff line number Diff line
@@ -765,9 +765,7 @@ void __i2400m_dev_reset_handle(struct work_struct *ws) 
		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;

		result = -EUCLEAN;

	}

out_unlock:

	if (i2400m->reset_ctx) {
@@ -775,6 +773,12 @@ out_unlock: 
		complete(&ctx->completion);

	}

	mutex_unlock(&i2400m->init_mutex);

	if (result == -EUCLEAN) {

		/* ops, need to clean up [w/ init_mutex not held] */

		result = i2400m->bus_reset(i2400m, I2400M_RT_BUS);

		if (result >= 0)

			result = -ENODEV;

	}

out:

	i2400m_put(i2400m);

	kfree(iw);

drivers/net/wimax/i2400m/i2400m.h

+3 −0
Original line number Diff line number Diff line
@@ -281,6 +281,9 @@ struct i2400m_barker_db; 
 *     process, so it cannot rely on common infrastructure being laid

 *     out.

 *

 *     IMPORTANT: don't call reset on RT_BUS with i2400m->init_mutex

 *     held, as the .pre/.post reset handlers will deadlock.

 *

 * @bus_bm_retries: [fill] How many times shall a firmware upload /

 *     device initialization be retried? Different models of the same

 *     device might need different values, hence it is set by the

drivers/net/wimax/i2400m/usb.c

+10 −4
Original line number Diff line number Diff line
@@ -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;