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authorAlan Stern <stern@rowland.harvard.edu>2007-03-15 15:50:34 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-15 15:29:26 -0700
commitd9a9cdfb078d755e648d53ec25b7370f84ee5729 (patch)
tree308380483fd6241b1d0ef5916b9329c1c5df00f6 /drivers
parent6ab27c6bf38d5ff71dafeca77b79e7c284804b75 (diff)
downloadop-kernel-dev-d9a9cdfb078d755e648d53ec25b7370f84ee5729.zip
op-kernel-dev-d9a9cdfb078d755e648d53ec25b7370f84ee5729.tar.gz
[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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/base/core.c29
-rw-r--r--drivers/s390/cio/ccwgroup.c18
-rw-r--r--drivers/scsi/scsi_sysfs.c14
3 files changed, 57 insertions, 4 deletions
diff --git a/drivers/base/core.c b/drivers/base/core.c
index f191afe..ad0f4a2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -407,6 +407,35 @@ void device_remove_bin_file(struct device *dev, struct bin_attribute *attr)
}
EXPORT_SYMBOL_GPL(device_remove_bin_file);
+/**
+ * device_schedule_callback - helper to schedule a callback for a device
+ * @dev: device.
+ * @func: callback function to invoke later.
+ *
+ * Attribute methods must not unregister themselves or their parent device
+ * (which would amount to the same thing). Attempts to do so will deadlock,
+ * since unregistration is mutually exclusive with driver callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @dev as its
+ * argument in the workqueue's process context. @dev will be pinned until
+ * @func returns.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated.
+ *
+ * NOTE: This routine won't work if CONFIG_SYSFS isn't set! It uses an
+ * underlying sysfs routine (since it is intended for use by attribute
+ * methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
+ */
+int device_schedule_callback(struct device *dev,
+ void (*func)(struct device *))
+{
+ return sysfs_schedule_callback(&dev->kobj,
+ (void (*)(void *)) func, dev);
+}
+EXPORT_SYMBOL_GPL(device_schedule_callback);
+
static void klist_children_get(struct klist_node *n)
{
struct device *dev = container_of(n, struct device, knode_parent);
diff --git a/drivers/s390/cio/ccwgroup.c b/drivers/s390/cio/ccwgroup.c
index d48e3ca..5aeb68e 100644
--- a/drivers/s390/cio/ccwgroup.c
+++ b/drivers/s390/cio/ccwgroup.c
@@ -71,19 +71,31 @@ __ccwgroup_remove_symlinks(struct ccwgroup_device *gdev)
* Provide an 'ungroup' attribute so the user can remove group devices no
* longer needed or accidentially created. Saves memory :)
*/
+static void ccwgroup_ungroup_callback(struct device *dev)
+{
+ struct ccwgroup_device *gdev = to_ccwgroupdev(dev);
+
+ __ccwgroup_remove_symlinks(gdev);
+ device_unregister(dev);
+}
+
static ssize_t
ccwgroup_ungroup_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
struct ccwgroup_device *gdev;
+ int rc;
gdev = to_ccwgroupdev(dev);
if (gdev->state != CCWGROUP_OFFLINE)
return -EINVAL;
- __ccwgroup_remove_symlinks(gdev);
- device_unregister(dev);
-
+ /* Note that we cannot unregister the device from one of its
+ * attribute methods, so we have to use this roundabout approach.
+ */
+ rc = device_schedule_callback(dev, ccwgroup_ungroup_callback);
+ if (rc)
+ count = rc;
return count;
}
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index c275dca..939de0d 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);
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