This corrects the kobject_add -EEXIST failure reported in
http://marc.info/?l=linux-scsi&m=117699334422336&w=2
Basically, there was a collision between async scsi scan's
scsi_sysfs_add_devices() and asynchronous scanning kicked off by the
fc transport's rport code. Both called scsi_sysfs_add_sdev() for the
same sdev.
The problem was that async scsi scan's call did not hold the scan_mutex
when making the call to scsi_sysfs_add_sdev(). Additionally, looking at
the shost->async_scan flag, which is critical for whether the sdev gets
enumerated or not, many uses were fuzzy. As a bit flag, it should have
been under the scsi_host lock, but via the way it's used within
scsi_scan.c, it should have been under the scan_mutex. It was positioned
within the async scan semaphore, which didn't help anything. Key to its
change, is that is done prior to releasing the scan_mutex after around
the scsi_sysfs_add_sdev() calls. To avoid all the lock repositioning,
I simply converted it to an atomic. A little overkill, but has the
coherency it needs.
Confirmed by Josef that it corrected his problems.
-- james s
Signed-off-by: James Smart <[EMAIL PROTECTED]>
diff -upNr a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
--- a/drivers/scsi/scsi_scan.c 2007-04-25 23:08:32.000000000 -0400
+++ b/drivers/scsi/scsi_scan.c 2007-05-04 18:35:58.000000000 -0400
@@ -1081,7 +1081,8 @@ static int scsi_probe_and_add_lun(struct
goto out_free_result;
}
- res = scsi_add_lun(sdev, result, &bflags, shost->async_scan);
+ res = scsi_add_lun(sdev, result, &bflags,
+ atomic_read(&shost->async_scan));
if (res == SCSI_SCAN_LUN_PRESENT) {
if (bflags & BLIST_KEY) {
sdev->lockable = 0;
@@ -1470,7 +1471,7 @@ struct scsi_device *__scsi_add_device(st
if (strncmp(scsi_scan_type, "none", 4) == 0)
return ERR_PTR(-ENODEV);
- if (!shost->async_scan)
+ if (!atomic_read(&shost->async_scan))
scsi_complete_async_scans();
starget = scsi_alloc_target(parent, channel, id);
@@ -1590,7 +1591,7 @@ void scsi_scan_target(struct device *par
if (strncmp(scsi_scan_type, "none", 4) == 0)
return;
- if (!shost->async_scan)
+ if (!atomic_read(&shost->async_scan))
scsi_complete_async_scans();
mutex_lock(&shost->scan_mutex);
@@ -1638,7 +1639,7 @@ int scsi_scan_host_selected(struct Scsi_
"%s: <%u:%u:%u>\n",
__FUNCTION__, channel, id, lun));
- if (!shost->async_scan)
+ if (!atomic_read(&shost->async_scan))
scsi_complete_async_scans();
if (((channel != SCAN_WILD_CARD) && (channel > shost->max_channel)) ||
@@ -1687,7 +1688,7 @@ static struct async_scan_data *scsi_prep
if (strncmp(scsi_scan_type, "sync", 4) == 0)
return NULL;
- if (shost->async_scan) {
+ if (atomic_read(&shost->async_scan)) {
printk("%s called twice for host %d", __FUNCTION__,
shost->host_no);
dump_stack();
@@ -1702,8 +1703,9 @@ static struct async_scan_data *scsi_prep
goto err;
init_completion(&data->prev_finished);
+ atomic_set(&shost->async_scan, 1);
+
spin_lock(&async_scan_lock);
- shost->async_scan = 1;
if (list_empty(&scanning_hosts))
complete(&data->prev_finished);
list_add_tail(&data->list, &scanning_hosts);
@@ -1732,7 +1734,7 @@ static void scsi_finish_async_scan(struc
return;
shost = data->shost;
- if (!shost->async_scan) {
+ if (!atomic_read(&shost->async_scan)) {
printk("%s called twice for host %d", __FUNCTION__,
shost->host_no);
dump_stack();
@@ -1741,10 +1743,12 @@ static void scsi_finish_async_scan(struc
wait_for_completion(&data->prev_finished);
+ mutex_lock(&shost->scan_mutex);
scsi_sysfs_add_devices(shost);
+ atomic_set(&shost->async_scan, 0);
+ mutex_unlock(&shost->scan_mutex);
spin_lock(&async_scan_lock);
- shost->async_scan = 0;
list_del(&data->list);
if (!list_empty(&scanning_hosts)) {
struct async_scan_data *next = list_entry(scanning_hosts.next,
diff -upNr a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
--- a/include/scsi/scsi_host.h 2007-04-25 23:08:32.000000000 -0400
+++ b/include/scsi/scsi_host.h 2007-05-04 17:48:48.000000000 -0400
@@ -6,6 +6,7 @@
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
+#include <asm/atomic.h>
struct request_queue;
struct block_device;
@@ -605,7 +606,7 @@ struct Scsi_Host {
unsigned tmf_in_progress:1;
/* Asynchronous scan in progress */
- unsigned async_scan:1;
+ atomic_t async_scan;
/*
* Optional work queue to be utilized by the transport
-
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