cxl: Prove CXL locking

When CONFIG_PROVE_LOCKING is enabled the 'struct device' definition gets
an additional mutex that is not clobbered by
lockdep_set_novalidate_class() like the typical device_lock(). This
allows for local annotation of subsystem locks with mutex_lock_nested()
per the subsystem's object/lock hierarchy. For CXL, this primarily needs
the ability to lock ports by depth and child objects of ports by their
parent parent-port lock.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/164365853422.99383.1052399160445197427.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index 4e80865..93d1dc5 100644 (file)
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -176,14 +176,14 @@ static struct cxl_dport *find_dport_by_dev(struct cxl_port *port, struct device
 {
        struct cxl_dport *dport;
 
-       device_lock(&port->dev);
+       cxl_device_lock(&port->dev);
        list_for_each_entry(dport, &port->dports, list)
                if (dport->dport == dev) {
-                       device_unlock(&port->dev);
+                       cxl_device_unlock(&port->dev);
                        return dport;
                }
 
-       device_unlock(&port->dev);
+       cxl_device_unlock(&port->dev);
        return NULL;
 }
 
@@ -264,9 +264,9 @@ static int add_host_bridge_uport(struct device *match, void *arg)
        if (IS_ERR(cxld))
                return PTR_ERR(cxld);
 
-       device_lock(&port->dev);
+       cxl_device_lock(&port->dev);
        dport = list_first_entry(&port->dports, typeof(*dport), list);
-       device_unlock(&port->dev);
+       cxl_device_unlock(&port->dev);
 
        single_port_map[0] = dport->port_id;
 

diff --git a/drivers/cxl/core/pmem.c b/drivers/cxl/core/pmem.c
index b5fca97..40b3f50 100644 (file)
--- a/drivers/cxl/core/pmem.c
+++ b/drivers/cxl/core/pmem.c
@@ -115,10 +115,10 @@ static void unregister_nvb(void *_cxl_nvb)
         * work to flush. Once the state has been changed to 'dead' then no new
         * work can be queued by user-triggered bind.
         */
-       device_lock(&cxl_nvb->dev);
+       cxl_device_lock(&cxl_nvb->dev);
        flush = cxl_nvb->state != CXL_NVB_NEW;
        cxl_nvb->state = CXL_NVB_DEAD;
-       device_unlock(&cxl_nvb->dev);
+       cxl_device_unlock(&cxl_nvb->dev);
 
        /*
         * Even though the device core will trigger device_release_driver()

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index f287d87..9285cdb 100644 (file)
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -111,7 +111,7 @@ static ssize_t target_list_show(struct device *dev,
        ssize_t offset = 0;
        int i, rc = 0;
 
-       device_lock(dev);
+       cxl_device_lock(dev);
        for (i = 0; i < cxld->interleave_ways; i++) {
                struct cxl_dport *dport = cxld->target[i];
                struct cxl_dport *next = NULL;
@@ -127,7 +127,7 @@ static ssize_t target_list_show(struct device *dev,
                        break;
                offset += rc;
        }
-       device_unlock(dev);
+       cxl_device_unlock(dev);
 
        if (rc < 0)
                return rc;
@@ -214,6 +214,12 @@ bool is_root_decoder(struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(is_root_decoder, CXL);
 
+bool is_cxl_decoder(struct device *dev)
+{
+       return dev->type->release == cxl_decoder_release;
+}
+EXPORT_SYMBOL_NS_GPL(is_cxl_decoder, CXL);
+
 struct cxl_decoder *to_cxl_decoder(struct device *dev)
 {
        if (dev_WARN_ONCE(dev, dev->type->release != cxl_decoder_release,
@@ -235,10 +241,10 @@ static void cxl_port_release(struct device *dev)
        struct cxl_port *port = to_cxl_port(dev);
        struct cxl_dport *dport, *_d;
 
-       device_lock(dev);
+       cxl_device_lock(dev);
        list_for_each_entry_safe(dport, _d, &port->dports, list)
                cxl_dport_release(dport);
-       device_unlock(dev);
+       cxl_device_unlock(dev);
        ida_free(&cxl_port_ida, port->id);
        kfree(port);
 }
@@ -254,6 +260,12 @@ static const struct device_type cxl_port_type = {
        .groups = cxl_port_attribute_groups,
 };
 
+bool is_cxl_port(struct device *dev)
+{
+       return dev->type == &cxl_port_type;
+}
+EXPORT_SYMBOL_NS_GPL(is_cxl_port, CXL);
+
 struct cxl_port *to_cxl_port(struct device *dev)
 {
        if (dev_WARN_ONCE(dev, dev->type != &cxl_port_type,
@@ -261,13 +273,14 @@ struct cxl_port *to_cxl_port(struct device *dev)
                return NULL;
        return container_of(dev, struct cxl_port, dev);
 }
+EXPORT_SYMBOL_NS_GPL(to_cxl_port, CXL);
 
 static void unregister_port(void *_port)
 {
        struct cxl_port *port = _port;
        struct cxl_dport *dport;
 
-       device_lock(&port->dev);
+       cxl_device_lock(&port->dev);
        list_for_each_entry(dport, &port->dports, list) {
                char link_name[CXL_TARGET_STRLEN];
 
@@ -276,7 +289,7 @@ static void unregister_port(void *_port)
                        continue;
                sysfs_remove_link(&port->dev.kobj, link_name);
        }
-       device_unlock(&port->dev);
+       cxl_device_unlock(&port->dev);
        device_unregister(&port->dev);
 }
 
@@ -407,7 +420,7 @@ static int add_dport(struct cxl_port *port, struct cxl_dport *new)
 {
        struct cxl_dport *dup;
 
-       device_lock(&port->dev);
+       cxl_device_lock(&port->dev);
        dup = find_dport(port, new->port_id);
        if (dup)
                dev_err(&port->dev,
@@ -416,7 +429,7 @@ static int add_dport(struct cxl_port *port, struct cxl_dport *new)
                        dev_name(dup->dport));
        else
                list_add_tail(&new->list, &port->dports);
-       device_unlock(&port->dev);
+       cxl_device_unlock(&port->dev);
 
        return dup ? -EEXIST : 0;
 }
@@ -475,7 +488,7 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
        if (!target_map)
                return 0;
 
-       device_lock(&port->dev);
+       cxl_device_lock(&port->dev);
        if (list_empty(&port->dports)) {
                rc = -EINVAL;
                goto out_unlock;
@@ -492,7 +505,7 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
        }
 
 out_unlock:
-       device_unlock(&port->dev);
+       cxl_device_unlock(&port->dev);
 
        return rc;
 }
@@ -717,15 +730,27 @@ static int cxl_bus_match(struct device *dev, struct device_driver *drv)
 
 static int cxl_bus_probe(struct device *dev)
 {
-       return to_cxl_drv(dev->driver)->probe(dev);
+       int rc;
+
+       /*
+        * Take the CXL nested lock since the driver core only holds
+        * @dev->mutex and not @dev->lockdep_mutex.
+        */
+       cxl_nested_lock(dev);
+       rc = to_cxl_drv(dev->driver)->probe(dev);
+       cxl_nested_unlock(dev);
+
+       return rc;
 }
 
 static void cxl_bus_remove(struct device *dev)
 {
        struct cxl_driver *cxl_drv = to_cxl_drv(dev->driver);
 
+       cxl_nested_lock(dev);
        if (cxl_drv->remove)
                cxl_drv->remove(dev);
+       cxl_nested_unlock(dev);
 }
 
 struct bus_type cxl_bus_type = {

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 7ade555..6a38d2e 100644 (file)
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -291,6 +291,7 @@ static inline bool is_cxl_root(struct cxl_port *port)
        return port->uport == port->dev.parent;
 }
 
+bool is_cxl_port(struct device *dev);
 struct cxl_port *to_cxl_port(struct device *dev);
 struct cxl_port *devm_cxl_add_port(struct device *host, struct device *uport,
                                   resource_size_t component_reg_phys,
@@ -301,6 +302,7 @@ int cxl_add_dport(struct cxl_port *port, struct device *dport, int port_id,
 
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 bool is_root_decoder(struct device *dev);
+bool is_cxl_decoder(struct device *dev);
 struct cxl_decoder *cxl_root_decoder_alloc(struct cxl_port *port,
                                           unsigned int nr_targets);
 struct cxl_decoder *cxl_switch_decoder_alloc(struct cxl_port *port,
@@ -353,4 +355,83 @@ struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_nvdimm *cxl_nvd);
 #ifndef __mock
 #define __mock static
 #endif
+
+#ifdef CONFIG_PROVE_CXL_LOCKING
+enum cxl_lock_class {
+       CXL_ANON_LOCK,
+       CXL_NVDIMM_LOCK,
+       CXL_NVDIMM_BRIDGE_LOCK,
+       CXL_PORT_LOCK,
+       /*
+        * Be careful to add new lock classes here, CXL_PORT_LOCK is
+        * extended by the port depth, so a maximum CXL port topology
+        * depth would need to be defined first.
+        */
+};
+
+static inline void cxl_nested_lock(struct device *dev)
+{
+       if (is_cxl_port(dev)) {
+               struct cxl_port *port = to_cxl_port(dev);
+
+               mutex_lock_nested(&dev->lockdep_mutex,
+                                 CXL_PORT_LOCK + port->depth);
+       } else if (is_cxl_decoder(dev)) {
+               struct cxl_port *port = to_cxl_port(dev->parent);
+
+               /*
+                * A decoder is the immediate child of a port, so set
+                * its lock class equal to other child device siblings.
+                */
+               mutex_lock_nested(&dev->lockdep_mutex,
+                                 CXL_PORT_LOCK + port->depth + 1);
+       } else if (is_cxl_nvdimm_bridge(dev))
+               mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_BRIDGE_LOCK);
+       else if (is_cxl_nvdimm(dev))
+               mutex_lock_nested(&dev->lockdep_mutex, CXL_NVDIMM_LOCK);
+       else
+               mutex_lock_nested(&dev->lockdep_mutex, CXL_ANON_LOCK);
+}
+
+static inline void cxl_nested_unlock(struct device *dev)
+{
+       mutex_unlock(&dev->lockdep_mutex);
+}
+
+static inline void cxl_device_lock(struct device *dev)
+{
+       /*
+        * For double lock errors the lockup will happen before lockdep
+        * warns at cxl_nested_lock(), so assert explicitly.
+        */
+       lockdep_assert_not_held(&dev->lockdep_mutex);
+
+       device_lock(dev);
+       cxl_nested_lock(dev);
+}
+
+static inline void cxl_device_unlock(struct device *dev)
+{
+       cxl_nested_unlock(dev);
+       device_unlock(dev);
+}
+#else
+static inline void cxl_nested_lock(struct device *dev)
+{
+}
+
+static inline void cxl_nested_unlock(struct device *dev)
+{
+}
+
+static inline void cxl_device_lock(struct device *dev)
+{
+       device_lock(dev);
+}
+
+static inline void cxl_device_unlock(struct device *dev)
+{
+       device_unlock(dev);
+}
+#endif
 #endif /* __CXL_H__ */

diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
index b65a272..15ad666 100644 (file)
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -43,7 +43,7 @@ static int cxl_nvdimm_probe(struct device *dev)
        if (!cxl_nvb)
                return -ENXIO;
 
-       device_lock(&cxl_nvb->dev);
+       cxl_device_lock(&cxl_nvb->dev);
        if (!cxl_nvb->nvdimm_bus) {
                rc = -ENXIO;
                goto out;
@@ -68,7 +68,7 @@ static int cxl_nvdimm_probe(struct device *dev)
        dev_set_drvdata(dev, nvdimm);
        rc = devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
 out:
-       device_unlock(&cxl_nvb->dev);
+       cxl_device_unlock(&cxl_nvb->dev);
        put_device(&cxl_nvb->dev);
 
        return rc;
@@ -233,7 +233,7 @@ static void cxl_nvb_update_state(struct work_struct *work)
        struct nvdimm_bus *victim_bus = NULL;
        bool release = false, rescan = false;
 
-       device_lock(&cxl_nvb->dev);
+       cxl_device_lock(&cxl_nvb->dev);
        switch (cxl_nvb->state) {
        case CXL_NVB_ONLINE:
                if (!online_nvdimm_bus(cxl_nvb)) {
@@ -251,7 +251,7 @@ static void cxl_nvb_update_state(struct work_struct *work)
        default:
                break;
        }
-       device_unlock(&cxl_nvb->dev);
+       cxl_device_unlock(&cxl_nvb->dev);
 
        if (release)
                device_release_driver(&cxl_nvb->dev);
@@ -327,9 +327,9 @@ static int cxl_nvdimm_bridge_reset(struct device *dev, void *data)
                return 0;
 
        cxl_nvb = to_cxl_nvdimm_bridge(dev);
-       device_lock(dev);
+       cxl_device_lock(dev);
        cxl_nvb->state = CXL_NVB_NEW;
-       device_unlock(dev);
+       cxl_device_unlock(dev);
 
        return 0;
 }

diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
index a11850d..2650a85 100644 (file)
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -185,7 +185,7 @@ static inline void devm_nsio_disable(struct device *dev,
 }
 #endif
 
-#ifdef CONFIG_PROVE_LOCKING
+#ifdef CONFIG_PROVE_NVDIMM_LOCKING
 extern struct class *nd_class;
 
 enum {

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 14b89aa..7dea203 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1516,6 +1516,29 @@ config CSD_LOCK_WAIT_DEBUG
          include the IPI handler function currently executing (if any)
          and relevant stack traces.
 
+choice
+       prompt "Lock debugging: prove subsystem device_lock() correctness"
+       depends on PROVE_LOCKING
+       help
+         For subsystems that have instrumented their usage of the device_lock()
+         with nested annotations, enable lock dependency checking. The locking
+         hierarchy 'subclass' identifiers are not compatible across
+         sub-systems, so only one can be enabled at a time.
+
+config PROVE_NVDIMM_LOCKING
+       bool "NVDIMM"
+       depends on LIBNVDIMM
+       help
+         Enable lockdep to validate nd_device_lock() usage.
+
+config PROVE_CXL_LOCKING
+       bool "CXL"
+       depends on CXL_BUS
+       help
+         Enable lockdep to validate cxl_device_lock() usage.
+
+endchoice
+
 endmenu # lock debugging
 
 config TRACE_IRQFLAGS