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cxl: Prove CXL locking
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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 <[email protected]>
Reviewed-by: Ben Widawsky <[email protected]>
Link: https://lore.kernel.org/r/164365853422.99383.1052399160445197427.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <[email protected]>
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@djbw
djbw committed Feb 9, 2022
1 parent 53fa1bf commit 3c5b903
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Showing 7 changed files with 154 additions and 25 deletions.
10 changes: 5 additions & 5 deletions drivers/cxl/acpi.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;

Expand Down
4 changes: 2 additions & 2 deletions drivers/cxl/core/pmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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()
Expand Down
47 changes: 36 additions & 11 deletions drivers/cxl/core/port.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -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,
Expand All @@ -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);
}
Expand All @@ -254,20 +260,27 @@ 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,
"not a cxl_port device\n"))
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];

Expand All @@ -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);
}

Expand Down Expand Up @@ -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,
Expand All @@ -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;
}
Expand Down Expand Up @@ -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;
Expand All @@ -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;
}
Expand Down Expand Up @@ -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 = {
Expand Down
81 changes: 81 additions & 0 deletions drivers/cxl/cxl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand All @@ -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,
Expand Down Expand Up @@ -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__ */
12 changes: 6 additions & 6 deletions drivers/cxl/pmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -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)) {
Expand All @@ -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);
Expand Down Expand Up @@ -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;
}
Expand Down
2 changes: 1 addition & 1 deletion drivers/nvdimm/nd-core.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down
23 changes: 23 additions & 0 deletions lib/Kconfig.debug
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down

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