[PATCH 5.19 0059/1157] usbnet: smsc95xx: Fix deadlock on runtime resume

Greg Kroah-Hartman
2022-08-15T22:00:00Z

From: Lukas Wunner <lukas@wunner.de>

commit 7b960c967f2aa01ab8f45c5a0bd78e754cffdeee upstream.

Commit 05b35e7eb9a1 ("smsc95xx: add phylib support") amended
smsc95xx_resume() to call phy_init_hw(). That function waits for the
device to runtime resume even though it is placed in the runtime resume
path, causing a deadlock.

The problem is that phy_init_hw() calls down to smsc95xx_mdiobus_read(),
which never uses the _nopm variant of usbnet_read_cmd().

Commit b4df480f68ae ("usbnet: smsc95xx: add reset_resume function with
reset operation") causes a similar deadlock on resume if the device was
already runtime suspended when entering system sleep:

That's because the commit introduced smsc95xx_reset_resume(), which
calls down to smsc95xx_reset(), which neglects to use _nopm accessors.

Fix by auto-detecting whether a device access is performed by the
suspend/resume task_struct and use the _nopm variant if so. This works
because the PM core guarantees that suspend/resume callbacks are run in
task context.

Stacktrace for posterity:

INFO: task kworker/2:1:49 blocked for more than 122 seconds.
Workqueue: usb_hub_wq hub_event
schedule
rpm_resume
__pm_runtime_resume
usb_autopm_get_interface
usbnet_read_cmd
__smsc95xx_read_reg
__smsc95xx_phy_wait_not_busy
__smsc95xx_mdio_read
smsc95xx_mdiobus_read
__mdiobus_read
mdiobus_read
smsc_phy_reset
phy_init_hw
smsc95xx_resume
usb_resume_interface
usb_resume_both
usb_runtime_resume
__rpm_callback
rpm_callback
rpm_resume
__pm_runtime_resume
usb_autoresume_device
hub_event
process_one_work

Fixes: b4df480f68ae ("usbnet: smsc95xx: add reset_resume function with reset operation")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v3.16+
Cc: Andre Edich <andre.edich@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/usb/smsc95xx.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -71,6 +71,7 @@ struct smsc95xx_priv {
struct fwnode_handle *irqfwnode;
struct mii_bus *mdiobus;
struct phy_device *phydev;
+ struct task_struct *pm_task;
};

static bool turbo_mode = true;
@@ -80,13 +81,14 @@ MODULE_PARM_DESC(turbo_mode, "Enable mul
static int __must_check __smsc95xx_read_reg(struct usbnet *dev, u32 index,
u32 *data, int in_pm)
{
+ struct smsc95xx_priv *pdata = dev->driver_priv;
u32 buf;
int ret;
int (*fn)(struct usbnet *, u8, u8, u16, u16, void *, u16);

BUG_ON(!dev);

- if (!in_pm)
+ if (current != pdata->pm_task)
fn = usbnet_read_cmd;
else
fn = usbnet_read_cmd_nopm;
@@ -110,13 +112,14 @@ static int __must_check __smsc95xx_read_
static int __must_check __smsc95xx_write_reg(struct usbnet *dev, u32 index,
u32 data, int in_pm)
{
+ struct smsc95xx_priv *pdata = dev->driver_priv;
u32 buf;
int ret;
int (*fn)(struct usbnet *, u8, u8, u16, u16, const void *, u16);

BUG_ON(!dev);

- if (!in_pm)
+ if (current != pdata->pm_task)
fn = usbnet_write_cmd;
else
fn = usbnet_write_cmd_nopm;
@@ -1490,9 +1493,12 @@ static int smsc95xx_suspend(struct usb_i
u32 val, link_up;
int ret;

+ pdata->pm_task = current;
+
ret = usbnet_suspend(intf, message);
if (ret < 0) {
netdev_warn(dev->net, "usbnet_suspend error\n");
+ pdata->pm_task = NULL;
return ret;
}

@@ -1732,6 +1738,7 @@ done:
if (ret && PMSG_IS_AUTO(message))
usbnet_resume(intf);

+ pdata->pm_task = NULL;
return ret;
}

@@ -1752,29 +1759,31 @@ static int smsc95xx_resume(struct usb_in
/* do this first to ensure it's cleared even in error case */
pdata->suspend_flags = 0;

+ pdata->pm_task = current;
+
if (suspend_flags & SUSPEND_ALLMODES) {
/* clear wake-up sources */
ret = smsc95xx_read_reg_nopm(dev, WUCSR, &val);
if (ret < 0)
- return ret;
+ goto done;

val &= ~(WUCSR_WAKE_EN_ | WUCSR_MPEN_);

ret = smsc95xx_write_reg_nopm(dev, WUCSR, val);
if (ret < 0)
- return ret;
+ goto done;

/* clear wake-up status */
ret = smsc95xx_read_reg_nopm(dev, PM_CTRL, &val);
if (ret < 0)
- return ret;
+ goto done;

val &= ~PM_CTL_WOL_EN_;
val |= PM_CTL_WUPS_;

ret = smsc95xx_write_reg_nopm(dev, PM_CTRL, val);
if (ret < 0)
- return ret;
+ goto done;
}

phy_init_hw(pdata->phydev);
@@ -1783,15 +1792,20 @@ static int smsc95xx_resume(struct usb_in
if (ret < 0)
netdev_warn(dev->net, "usbnet_resume error\n");

+done:
+ pdata->pm_task = NULL;
return ret;
}

static int smsc95xx_reset_resume(struct usb_interface *intf)
{
struct usbnet *dev = usb_get_intfdata(intf);
+ struct smsc95xx_priv *pdata = dev->driver_priv;
int ret;

+ pdata->pm_task = current;
ret = smsc95xx_reset(dev);
+ pdata->pm_task = NULL;
if (ret < 0)
return ret;