fix a deadlock issue when poking "eject" file

"/sys/devices/LNXSYSTM:00/.../eject" is used to evaluate _EJx method
and eject a device in user space.
But system hangs when poking the "eject" file because that
the device hot-removal code invoke the driver .remove method which will
try to remove the "eject" file as a result.

Queues the hot-removal function for deferred execution in this patch.
http://bugzilla.kernel.org/show_bug.cgi?id=9772

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 6d85289..9a84ed2 100644 (file)
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -6,6 +6,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/acpi.h>
+#include <asm/signal.h>
 
 #include <acpi/acpi_drivers.h>
 #include <acpi/acinterp.h>     /* for acpi_ex_eisa_id_to_string() */
@@ -92,17 +93,37 @@ acpi_device_modalias_show(struct device *dev, struct device_attribute *attr, cha
 }
 static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
 
-static int acpi_eject_operation(acpi_handle handle, int lockable)
+static int acpi_bus_hot_remove_device(void *context)
 {
+       struct acpi_device *device;
+       acpi_handle handle = context;
        struct acpi_object_list arg_list;
        union acpi_object arg;
        acpi_status status = AE_OK;
 
-       /*
-        * TBD: evaluate _PS3?
-        */
+       if (acpi_bus_get_device(handle, &device))
+               return 0;
 
-       if (lockable) {
+       if (!device)
+               return 0;
+
+       ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+               "Hot-removing device %s...\n", device->dev.bus_id));
+
+
+       if (acpi_bus_trim(device, 1)) {
+               ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
+                               "Removing device failed\n"));
+               return -1;
+       }
+
+       /* power off device */
+       status = acpi_evaluate_object(handle, "_PS3", NULL, NULL);
+       if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
+               ACPI_DEBUG_PRINT((ACPI_DB_WARN,
+                               "Power-off device failed\n"));
+
+       if (device->flags.lockable) {
                arg_list.count = 1;
                arg_list.pointer = &arg;
                arg.type = ACPI_TYPE_INTEGER;
@@ -118,24 +139,19 @@ static int acpi_eject_operation(acpi_handle handle, int lockable)
        /*
         * TBD: _EJD support.
         */
-
        status = acpi_evaluate_object(handle, "_EJ0", &arg_list, NULL);
-       if (ACPI_FAILURE(status)) {
-               return (-ENODEV);
-       }
+       if (ACPI_FAILURE(status))
+               return -ENODEV;
 
-       return (0);
+       return 0;
 }
 
 static ssize_t
 acpi_eject_store(struct device *d, struct device_attribute *attr,
                const char *buf, size_t count)
 {
-       int result;
        int ret = count;
-       int islockable;
        acpi_status status;
-       acpi_handle handle;
        acpi_object_type type = 0;
        struct acpi_device *acpi_device = to_acpi_device(d);
 
@@ -154,17 +170,9 @@ acpi_eject_store(struct device *d, struct device_attribute *attr,
                goto err;
        }
 
-       islockable = acpi_device->flags.lockable;
-       handle = acpi_device->handle;
-
-       result = acpi_bus_trim(acpi_device, 1);
-
-       if (!result)
-               result = acpi_eject_operation(handle, islockable);
-
-       if (result) {
-               ret = -EBUSY;
-       }
+       /* remove the device in another thread to fix the deadlock issue */
+       ret = kernel_thread(acpi_bus_hot_remove_device,
+                               acpi_device->handle, SIGCHLD);
       err:
        return ret;
 }