alloc_acpi_hotplug_work() is used to move event handler from
kacpi_notify_wq to kacpi_hotplug_wq, so the event handler could
call acpi_remove_notify_handler() to unreigster itself, otherwise
it will deaklock. But alloc_acpi_hotplug_work() mechanism introduces
a small race window as below:
1. kacpi_notify_wq invokes the wrapper event handler, which enqueues
the real event handler onto kacpi_hotplug_wq by calling
alloc_acpi_hotplug_work().
2. Another thread calls acpi_remove_notify_handler() and releases
all resources used by the real event handler.
3. kacpi_hotplug_wq invokes the real event handler, which may access
the already released resources now.
This patch tries to close the small race window.
Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
---
drivers/pci/hotplug/acpiphp.h | 7 ++++-
drivers/pci/hotplug/acpiphp_glue.c | 50 +++++++++++++++++++++++++++++++----
2 files changed, 50 insertions(+), 7 deletions(-)
diff --git a/drivers/pci/hotplug/acpiphp.h b/drivers/pci/hotplug/acpiphp.h
index 1a62e7b..ca2da17 100644
--- a/drivers/pci/hotplug/acpiphp.h
+++ b/drivers/pci/hotplug/acpiphp.h
@@ -37,6 +37,7 @@
#include <linux/acpi.h>
#include <linux/mutex.h>
+#include <linux/kref.h>
#include <linux/pci_hotplug.h>
#define dbg(format, arg...) \
@@ -74,6 +75,7 @@ static inline const char *slot_name(struct slot *slot)
struct acpiphp_bridge {
struct list_head list;
acpi_handle handle;
+ struct kref kref;
struct acpiphp_slot *slots;
/* Ejectable PCI-to-PCI bridge (PCI bridge and PCI function) */
@@ -124,6 +126,7 @@ struct acpiphp_func {
struct list_head sibling;
struct notifier_block nb;
acpi_handle handle;
+ struct kref kref;
u8 function; /* pci function# */
u32 flags; /* see below */
@@ -160,6 +163,7 @@ struct acpiphp_attention_info
#define BRIDGE_HAS_PS1 (0x00000020)
#define BRIDGE_HAS_PS2 (0x00000040)
#define BRIDGE_HAS_PS3 (0x00000080)
+#define BRIDGE_IS_DEAD (0x80000000)
/* slot flags */
@@ -175,7 +179,8 @@ struct acpiphp_attention_info
#define FUNC_HAS_PS1 (0x00000020)
#define FUNC_HAS_PS2 (0x00000040)
#define FUNC_HAS_PS3 (0x00000080)
-#define FUNC_HAS_DCK (0x00000100)
+#define FUNC_HAS_DCK (0x00000100)
+#define FUNC_IS_DEAD (0x80000000)
/* function prototypes */
diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 003a6d5..764891e 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -115,6 +115,14 @@ static const struct acpi_dock_ops acpiphp_dock_ops = {
.handler = handle_hotplug_event_func,
};
+static void acpiphp_release_func(struct kref *kref)
+{
+ struct acpiphp_func *func;
+
+ func = container_of(kref, struct acpiphp_func, kref);
+ kfree(func);
+}
+
/* callback routine to register each ACPI PCI slot object */
static acpi_status
register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
@@ -153,6 +161,7 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
return AE_NO_MEMORY;
INIT_LIST_HEAD(&newfunc->sibling);
+ kref_init(&newfunc->kref);
newfunc->handle = handle;
newfunc->function = function;
@@ -191,7 +200,7 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
if (!slot) {
slot = kzalloc(sizeof(struct acpiphp_slot), GFP_KERNEL);
if (!slot) {
- kfree(newfunc);
+ kref_put(&newfunc->kref, acpiphp_release_func);
return AE_NO_MEMORY;
}
@@ -266,7 +275,7 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
bridge->nr_slots--;
bridge->slots = slot->next;
kfree(slot);
- kfree(newfunc);
+ kref_put(&newfunc->kref, acpiphp_release_func);
return AE_OK;
}
@@ -371,8 +380,16 @@ static inline void config_p2p_bridge_flags(struct acpiphp_bridge *bridge)
}
}
+static void acpiphp_release_bridge(struct kref *kref)
+{
+ struct acpiphp_bridge *bridge;
+
+ bridge = container_of(kref, struct acpiphp_bridge, kref);
+ kfree(bridge);
+}
+
/* allocate and initialize PCI-to-PCI bridge data structure */
-static void add_p2p_bridge(acpi_handle *handle)
+static void add_p2p_bridge(acpi_handle handle)
{
struct acpiphp_bridge *bridge;
@@ -382,6 +399,7 @@ static void add_p2p_bridge(acpi_handle *handle)
return;
}
+ kref_init(&bridge->kref);
bridge->handle = handle;
config_p2p_bridge_flags(bridge);
@@ -403,7 +421,7 @@ static void add_p2p_bridge(acpi_handle *handle)
return;
err:
pci_dev_put(bridge->pci_dev);
- kfree(bridge);
+ kref_put(&bridge->kref, acpiphp_release_bridge);
return;
}
@@ -515,7 +533,8 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
err("failed to remove notify handler\n");
}
list_del(&func->sibling);
- kfree(func);
+ func->flags |= FUNC_IS_DEAD;
+ kref_put(&func->kref, acpiphp_release_func);
}
acpiphp_unregister_hotplug_slot(slot);
list_del(&slot->funcs);
@@ -531,7 +550,8 @@ static void cleanup_bridge(struct acpiphp_bridge *bridge)
pci_dev_put(bridge->pci_dev);
list_del(&bridge->list);
- kfree(bridge);
+ bridge->flags |= BRIDGE_IS_DEAD;
+ kref_put(&bridge->kref, acpiphp_release_bridge);
}
static acpi_status
@@ -1075,6 +1095,8 @@ static void _handle_hotplug_event_bridge(struct work_struct *work)
handle = hp_work->handle;
type = hp_work->type;
bridge = (struct acpiphp_bridge *)hp_work->context;
+ if (bridge->flags & BRIDGE_IS_DEAD)
+ goto out;
acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
@@ -1133,6 +1155,8 @@ static void _handle_hotplug_event_bridge(struct work_struct *work)
break;
}
+out:
+ kref_put(&bridge->kref, acpiphp_release_bridge);
kfree(hp_work); /* allocated in handle_hotplug_event_bridge */
}
@@ -1147,6 +1171,11 @@ 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 = (struct acpiphp_bridge *)context;
+
+ /* Will be released by _handle_hotplug_event_bridge() */
+ kref_get(&bridge->kref);
+
/*
* Currently the code adds all hotplug events to the kacpid_wq
* queue when it should add hotplug events to the kacpi_hotplug_wq.
@@ -1172,6 +1201,8 @@ static void _handle_hotplug_event_func(struct work_struct *work)
handle = hp_work->handle;
type = hp_work->type;
func = (struct acpiphp_func *)hp_work->context;
+ if (func->flags & FUNC_IS_DEAD)
+ goto out;
acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);
@@ -1205,6 +1236,8 @@ static void _handle_hotplug_event_func(struct work_struct *work)
break;
}
+out:
+ kref_put(&func->kref, acpiphp_release_func);
kfree(hp_work); /* allocated in handle_hotplug_event_func */
}
@@ -1219,6 +1252,11 @@ 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 = (struct acpiphp_func *)context;
+
+ /* Will be released by _handle_hotplug_event_func() */
+ kref_get(&func->kref);
+
/*
* Currently the code adds all hotplug events to the kacpid_wq
* queue when it should add hotplug events to the kacpi_hotplug_wq.
--
1.7.5.4
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