[PATCH v3 01/10] i2c: i2c-smbus: prevent races on remove when Host Notify is used
From: Benjamin Tissoires <hidden>
Date: 2016-09-28 08:16:09
Also in:
lkml
Subsystem:
i2c subsystem, i2c subsystem host drivers, i2c/smbus controller drivers for pc, the rest · Maintainers:
Wolfram Sang, Andi Shyti, Jean Delvare, Linus Torvalds
struct host_notify contains its own workqueue, so there is a race when the adapter gets removed: - the adapter schedules a notification - the notification is on hold - the adapter gets removed and all its children too - the worker fires and access illegal memory Add an API to actually kill the workqueue and prevent it to access such illegal memory. I couldn't find a reliable way of automatically calling this, so it's the responsibility of the adapter driver to clean up after itself. Signed-off-by: Benjamin Tissoires <redacted> --- no changes in v3 changes in v2: - changed i801_disable_host_notify() parameter - changed the comments to actually match the behavior --- drivers/i2c/busses/i2c-i801.c | 13 +++++++++++++ drivers/i2c/i2c-smbus.c | 19 +++++++++++++++++++ include/linux/i2c-smbus.h | 1 + 3 files changed, 33 insertions(+)
diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 22a0ed4..b494a85 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c@@ -959,6 +959,18 @@ static int i801_enable_host_notify(struct i2c_adapter *adapter) return 0; } +static void i801_disable_host_notify(struct i801_priv *priv) +{ + + if (!(priv->features & FEATURE_HOST_NOTIFY)) + return; + + /* disable Host Notify... */ + outb_p(0, SMBSLVCMD(priv)); + /* ...and process the already queued notifications */ + i2c_cancel_smbus_host_notify(priv->host_notify); +} + static const struct i2c_algorithm smbus_algorithm = { .smbus_xfer = i801_access, .functionality = i801_func,
@@ -1647,6 +1659,7 @@ static void i801_remove(struct pci_dev *dev) pm_runtime_forbid(&dev->dev); pm_runtime_get_noresume(&dev->dev); + i801_disable_host_notify(priv); i801_del_mux(priv); i2c_del_adapter(&priv->adapter); i801_acpi_remove(priv);
diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
index b0d2679..35e4f1a 100644
--- a/drivers/i2c/i2c-smbus.c
+++ b/drivers/i2c/i2c-smbus.c@@ -279,6 +279,8 @@ static void smbus_host_notify_work(struct work_struct *work) * Returns a struct smbus_host_notify pointer on success, and NULL on failure. * The resulting smbus_host_notify must not be freed afterwards, it is a * managed resource already. + * To prevent races on remove, the caller needs to stop the embedded worker + * by calling i2c_cancel_smbus_host_notify(). */ struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap) {
@@ -299,6 +301,23 @@ struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap) EXPORT_SYMBOL_GPL(i2c_setup_smbus_host_notify); /** + * i2c_cancel_smbus_host_notify - Terminate any active Host Notification. + * @host_notify: the host_notify object to terminate + * + * Process any pending Host Notifcation and prevent new ones to be added. + * Must be called to ensure no races between the adaptor being removed and + * the Host Notification being processed. + */ +void i2c_cancel_smbus_host_notify(struct smbus_host_notify *host_notify) +{ + if (!host_notify) + return; + + cancel_work_sync(&host_notify->work); +} +EXPORT_SYMBOL_GPL(i2c_cancel_smbus_host_notify); + +/** * i2c_handle_smbus_host_notify - Forward a Host Notify event to the correct * I2C client. * @host_notify: the struct host_notify attached to the relevant adapter
diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
index c2e3324..ac02827 100644
--- a/include/linux/i2c-smbus.h
+++ b/include/linux/i2c-smbus.h@@ -76,5 +76,6 @@ struct smbus_host_notify { struct smbus_host_notify *i2c_setup_smbus_host_notify(struct i2c_adapter *adap); int i2c_handle_smbus_host_notify(struct smbus_host_notify *host_notify, unsigned short addr, unsigned int data); +void i2c_cancel_smbus_host_notify(struct smbus_host_notify *host_notify); #endif /* _LINUX_I2C_SMBUS_H */
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2.7.4