[PATCH] sysfs and driver core: add callback helper, used by SCSI and S390

This patch (as868) adds a helper routine for device drivers that need
to set up a callback to perform some action in a different process's
context.  This is intended for use by attribute methods that want to
unregister themselves or their parent device.  Attribute method calls
are mutually exclusive with unregistration, so such actions cannot be
taken directly.

Two attribute methods are converted to use the new helper routine: one
for SCSI device deletion and one for System/390 ccwgroup devices.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index c275dcac3f1..939de0de18b 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -452,10 +452,22 @@ store_rescan_field (struct device *dev, struct device_attribute *attr, const cha
 }
 static DEVICE_ATTR(rescan, S_IWUSR, NULL, store_rescan_field);
 
+static void sdev_store_delete_callback(struct device *dev)
+{
+        scsi_remove_device(to_scsi_device(dev));
+}
+
 static ssize_t sdev_store_delete(struct device *dev, struct device_attribute *attr, const char *buf,
                                  size_t count)
 {
-        scsi_remove_device(to_scsi_device(dev));
+        int rc;
+
+        /* An attribute cannot be unregistered by one of its own methods,
+         * so we have to use this roundabout approach.
+         */
+        rc = device_schedule_callback(dev, sdev_store_delete_callback);
+        if (rc)
+                count = rc;
         return count;
 };
 static DEVICE_ATTR(delete, S_IWUSR, NULL, sdev_store_delete);