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scst, scst_vdisk: Revert "Simplify the code for querying the vdisk filename" (merge r9375 from trunk)

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git-svn-id: http://svn.code.sf.net/p/scst/svn/branches/3.4.x@9377 d57e44dd-8a1f-0410-8b47-8ef2f437770f
This commit is contained in:
Bart Van Assche
2021-04-13 16:27:34 +00:00
parent f4dfc85312
commit effdb66b80
3 changed files with 27 additions and 13 deletions
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8
scst/include/scst.h
View File

@@ -2712,6 +2712,14 @@ struct scst_device {
/* Set, if a strictly serialized cmd is waiting blocked */
unsigned int strictly_serialized_cmd_waiting:1;
/*
* Set, if this device is being unregistered. Useful to let sysfs
* attributes know when they should exit immediately to prevent
* possible deadlocks with their device unregistration waiting for
* their kobj last put.
*/
unsigned int dev_unregistering:1;
/*
* Set if ext blocking is pending. It is just shortcut for
* !list_empty(&dev->ext_blockers_list) to save a cache miss.

25
scst/src/dev_handlers/scst_vdisk.c
View File

@@ -8463,17 +8463,6 @@ static ssize_t vdisk_sysfs_rotational_show(struct kobject *kobj,
return pos;
}
static bool scst_dev_being_unregistered(struct scst_device *dev)
{
bool res;
mutex_lock(&scst_mutex);
res = list_empty(&dev->dev_list_entry);
mutex_unlock(&scst_mutex);
return res;
}
static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
{
int res = 0;
@@ -8491,7 +8480,7 @@ static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
* under scst_vdisk_mutex.
*/
while (!mutex_trylock(&scst_vdisk_mutex)) {
if (scst_dev_being_unregistered(dev)) {
if (dev->dev_unregistering) {
TRACE_MGMT_DBG("Skipping being unregistered dev %s",
dev->virt_name);
res = -ENOENT;
@@ -8502,6 +8491,18 @@ static int vdev_sysfs_process_get_filename(struct scst_sysfs_work_item *work)
goto out_put;
}
msleep(100);
/*
* We need to reread dev_unregistering from memory, hence
* prevent compiler from putting it in a register. Generally,
* it shouldn't happen, because the compiler isn't allowed to do
* such a transformation if any functions that can cause side
* effects are called between successive accesses, but let's be
* on the safe side. We can't cast dev_unregistering to
* volatile, because it has no effect we need, and can't cast
* it to *(volatile bool*)&, because it isn't possible to get
* address of a bit field.
*/
barrier();
}
virt_dev = dev->dh_priv;

7
scst/src/scst_main.c
View File

@@ -1195,6 +1195,8 @@ static void scst_unregister_device(struct scsi_device *scsidp)
goto out_unlock;
}
dev->dev_unregistering = 1;
list_del_init(&dev->dev_list_entry);
#ifdef CONFIG_SCST_FORWARD_MODE_PASS_THROUGH
@@ -1418,7 +1420,8 @@ out:
return res;
out_unreg:
list_del_init(&dev->dev_list_entry);
dev->dev_unregistering = 1;
list_del(&dev->dev_list_entry);
scst_assign_dev_handler(dev, &scst_null_devtype);
goto out_pr_clear_dev;
@@ -1471,6 +1474,8 @@ void scst_unregister_virtual_device(int id,
goto out_unlock;
}
dev->dev_unregistering = 1;
scst_cm_on_dev_unregister(dev);
list_del_init(&dev->dev_list_entry);