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PCI: acpiphp: Protect acpiphp data structures from concurrent updates
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Now acpiphp_enumerate_slots() and acpiphp_remove_slots() may be invoked
concurrently by the PCI core, so add a bridge_mutex and reference count
mechanism to protect acpiphp bridge/slot/function data structures.

To avoid deadlock, handle_hotplug_event_bridge() will requeue the
hotplug event onto the kacpi_hotplug_wq by calling alloc_acpi_hp_work().
But the workaround has introduced a minor race window because the
'bridge' passed to _handle_hotplug_event_bridge() may have already been
destroyed when _handle_hotplug_event_bridge() is actually executed by
the kacpi_hotplug_wq.  So hold a reference count on the passed 'bridge'.
Fix the same issue for handle_hotplug_event_func() too.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Yinghai Lu <yinghai@kernel.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Toshi Kani <toshi.kani@hp.com>
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Jiang Liu authored and Bjorn Helgaas committed Apr 16, 2013
1 parent ad41dd9 commit 3d54a31
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Showing 2 changed files with 78 additions and 18 deletions.
1 change: 1 addition & 0 deletions drivers/pci/hotplug/acpiphp.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,7 @@ static inline const char *slot_name(struct slot *slot)
struct acpiphp_bridge {
struct list_head list;
struct list_head slots;
struct kref ref;
acpi_handle handle;

/* Ejectable PCI-to-PCI bridge (PCI bridge and PCI function) */
Expand Down
95 changes: 77 additions & 18 deletions drivers/pci/hotplug/acpiphp_glue.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -54,13 +54,15 @@
#include "acpiphp.h"

static LIST_HEAD(bridge_list);
static DEFINE_MUTEX(bridge_mutex);

#define MY_NAME "acpiphp_glue"

static void handle_hotplug_event_bridge (acpi_handle, u32, void *);
static void acpiphp_sanitize_bus(struct pci_bus *bus);
static void acpiphp_set_hpp_values(struct pci_bus *bus);
static void handle_hotplug_event_func(acpi_handle handle, u32 type, void *context);
static void free_bridge(struct kref *kref);

/* callback routine to check for the existence of a pci dock device */
static acpi_status
Expand All @@ -76,6 +78,39 @@ is_pci_dock_device(acpi_handle handle, u32 lvl, void *context, void **rv)
}
}

static inline void get_bridge(struct acpiphp_bridge *bridge)
{
kref_get(&bridge->ref);
}

static inline void put_bridge(struct acpiphp_bridge *bridge)
{
kref_put(&bridge->ref, free_bridge);
}

static void free_bridge(struct kref *kref)
{
struct acpiphp_bridge *bridge;
struct acpiphp_slot *slot, *next;
struct acpiphp_func *func, *tmp;

bridge = container_of(kref, struct acpiphp_bridge, ref);

list_for_each_entry_safe(slot, next, &bridge->slots, node) {
list_for_each_entry_safe(func, tmp, &slot->funcs, sibling) {
kfree(func);
}
kfree(slot);
}

/* Release reference acquired by acpiphp_bridge_handle_to_function() */
if ((bridge->flags & BRIDGE_HAS_EJ0) && bridge->func)
put_bridge(bridge->func->slot->bridge);
put_device(&bridge->pci_bus->dev);
pci_dev_put(bridge->pci_dev);
kfree(bridge);
}

/*
* the _DCK method can do funny things... and sometimes not
* hah-hah funny.
Expand Down Expand Up @@ -171,15 +206,14 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
device = (adr >> 16) & 0xffff;
function = adr & 0xffff;

pdev = pbus->self;
pdev = bridge->pci_dev;
if (pdev && device_is_managed_by_native_pciehp(pdev))
return AE_OK;

newfunc = kzalloc(sizeof(struct acpiphp_func), GFP_KERNEL);
if (!newfunc)
return AE_NO_MEMORY;

INIT_LIST_HEAD(&newfunc->sibling);
newfunc->handle = handle;
newfunc->function = function;

Expand Down Expand Up @@ -229,7 +263,9 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
INIT_LIST_HEAD(&slot->funcs);
mutex_init(&slot->crit_sect);

mutex_lock(&bridge_mutex);
list_add_tail(&slot->node, &bridge->slots);
mutex_unlock(&bridge_mutex);
bridge->nr_slots++;

dbg("found ACPI PCI Hotplug slot %llu at PCI %04x:%02x:%02x\n",
Expand All @@ -247,7 +283,9 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
}

newfunc->slot = slot;
mutex_lock(&bridge_mutex);
list_add_tail(&newfunc->sibling, &slot->funcs);
mutex_unlock(&bridge_mutex);

if (pci_bus_read_dev_vendor_id(pbus, PCI_DEVFN(device, function),
&val, 60*1000))
Expand Down Expand Up @@ -288,7 +326,9 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)

err_exit:
bridge->nr_slots--;
mutex_lock(&bridge_mutex);
list_del(&slot->node);
mutex_unlock(&bridge_mutex);
kfree(slot);
kfree(newfunc);

Expand All @@ -313,13 +353,17 @@ static void init_bridge_misc(struct acpiphp_bridge *bridge)
acpi_status status;

/* must be added to the list prior to calling register_slot */
mutex_lock(&bridge_mutex);
list_add(&bridge->list, &bridge_list);
mutex_unlock(&bridge_mutex);

/* register all slot objects under this bridge */
status = acpi_walk_namespace(ACPI_TYPE_DEVICE, bridge->handle, (u32)1,
register_slot, NULL, bridge, NULL);
if (ACPI_FAILURE(status)) {
mutex_lock(&bridge_mutex);
list_del(&bridge->list);
mutex_unlock(&bridge_mutex);
return;
}

Expand Down Expand Up @@ -349,16 +393,21 @@ static struct acpiphp_func *acpiphp_bridge_handle_to_function(acpi_handle handle
{
struct acpiphp_bridge *bridge;
struct acpiphp_slot *slot;
struct acpiphp_func *func;
struct acpiphp_func *func = NULL;

mutex_lock(&bridge_mutex);
list_for_each_entry(bridge, &bridge_list, list) {
list_for_each_entry(slot, &bridge->slots, node) {
list_for_each_entry(func, &slot->funcs, sibling) {
if (func->handle == handle)
if (func->handle == handle) {
get_bridge(func->slot->bridge);
mutex_unlock(&bridge_mutex);
return func;
}
}
}
}
mutex_unlock(&bridge_mutex);

return NULL;
}
Expand All @@ -368,17 +417,22 @@ static struct acpiphp_bridge *acpiphp_handle_to_bridge(acpi_handle handle)
{
struct acpiphp_bridge *bridge;

mutex_lock(&bridge_mutex);
list_for_each_entry(bridge, &bridge_list, list)
if (bridge->handle == handle)
if (bridge->handle == handle) {
get_bridge(bridge);
mutex_unlock(&bridge_mutex);
return bridge;
}
mutex_unlock(&bridge_mutex);

return NULL;
}

static void cleanup_bridge(struct acpiphp_bridge *bridge)
{
struct acpiphp_slot *slot, *next;
struct acpiphp_func *func, *tmp;
struct acpiphp_slot *slot;
struct acpiphp_func *func;
acpi_status status;
acpi_handle handle = bridge->handle;

Expand All @@ -399,8 +453,8 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
err("failed to install interrupt notify handler\n");
}

list_for_each_entry_safe(slot, next, &bridge->slots, node) {
list_for_each_entry_safe(func, tmp, &slot->funcs, sibling) {
list_for_each_entry(slot, &bridge->slots, node) {
list_for_each_entry(func, &slot->funcs, sibling) {
if (is_dock_device(func->handle)) {
unregister_hotplug_dock_device(func->handle);
unregister_dock_notifier(&func->nb);
Expand All @@ -412,18 +466,13 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
if (ACPI_FAILURE(status))
err("failed to remove notify handler\n");
}
list_del(&func->sibling);
kfree(func);
}
acpiphp_unregister_hotplug_slot(slot);
list_del(&slot->funcs);
kfree(slot);
}

put_device(&bridge->pci_bus->dev);
pci_dev_put(bridge->pci_dev);
mutex_lock(&bridge_mutex);
list_del(&bridge->list);
kfree(bridge);
mutex_unlock(&bridge_mutex);
}

static int power_on_slot(struct acpiphp_slot *slot)
Expand Down Expand Up @@ -620,7 +669,6 @@ static int __ref enable_device(struct acpiphp_slot *slot)
struct pci_dev *dev;
struct pci_bus *bus = slot->bridge->pci_bus;
struct acpiphp_func *func;
int retval = 0;
int num, max, pass;

if (slot->flags & SLOT_ENABLED)
Expand Down Expand Up @@ -680,7 +728,7 @@ static int __ref enable_device(struct acpiphp_slot *slot)


err_exit:
return retval;
return 0;
}

/* return first device in slot, acquiring a reference on it */
Expand Down Expand Up @@ -897,6 +945,7 @@ check_sub_bridges(acpi_handle handle, u32 lvl, void *context, void **rv)
dbg("%s: re-enumerating slots under %s\n",
__func__, objname);
acpiphp_check_bridge(bridge);
put_bridge(bridge);
}
return AE_OK ;
}
Expand Down Expand Up @@ -974,6 +1023,7 @@ static void _handle_hotplug_event_bridge(struct work_struct *work)

acpi_scan_lock_release();
kfree(hp_work); /* allocated in handle_hotplug_event_bridge */
put_bridge(bridge);
}

/**
Expand All @@ -987,6 +1037,8 @@ static void _handle_hotplug_event_bridge(struct work_struct *work)
static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
void *context)
{
struct acpiphp_bridge *bridge = context;

/*
* Currently the code adds all hotplug events to the kacpid_wq
* queue when it should add hotplug events to the kacpi_hotplug_wq.
Expand All @@ -995,6 +1047,7 @@ static void handle_hotplug_event_bridge(acpi_handle handle, u32 type,
* For now just re-add this work to the kacpi_hotplug_wq so we
* don't deadlock on hotplug actions.
*/
get_bridge(bridge);
alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_bridge);
}

Expand Down Expand Up @@ -1049,6 +1102,7 @@ static void _handle_hotplug_event_func(struct work_struct *work)

acpi_scan_lock_release();
kfree(hp_work); /* allocated in handle_hotplug_event_func */
put_bridge(func->slot->bridge);
}

/**
Expand All @@ -1062,6 +1116,8 @@ static void _handle_hotplug_event_func(struct work_struct *work)
static void handle_hotplug_event_func(acpi_handle handle, u32 type,
void *context)
{
struct acpiphp_func *func = context;

/*
* Currently the code adds all hotplug events to the kacpid_wq
* queue when it should add hotplug events to the kacpi_hotplug_wq.
Expand All @@ -1070,6 +1126,7 @@ static void handle_hotplug_event_func(acpi_handle handle, u32 type,
* For now just re-add this work to the kacpi_hotplug_wq so we
* don't deadlock on hotplug actions.
*/
get_bridge(func->slot->bridge);
alloc_acpi_hp_work(handle, type, context, _handle_hotplug_event_func);
}

Expand All @@ -1095,6 +1152,7 @@ void acpiphp_enumerate_slots(struct pci_bus *bus, acpi_handle handle)
}

INIT_LIST_HEAD(&bridge->slots);
kref_init(&bridge->ref);
bridge->handle = handle;
bridge->pci_dev = pci_dev_get(bus->self);
bridge->pci_bus = bus;
Expand Down Expand Up @@ -1128,6 +1186,7 @@ void acpiphp_remove_slots(struct pci_bus *bus)
list_for_each_entry_safe(bridge, tmp, &bridge_list, list)
if (bridge->pci_bus == bus) {
cleanup_bridge(bridge);
put_bridge(bridge);
break;
}
}
Expand Down

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