[libata] locking rewrite (== fix)
A lot of power packed into a little patch.
This change eliminates the sharing between our controller-wide spinlock
and the SCSI core's Scsi_Host lock. As the locking in libata was
already highly compartmentalized, always referencing our own lock, and
never scsi_host::host_lock.
As a side effect, this change eliminates a deadlock from calling
scsi_finish_command() while inside our spinlock.
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 1e3792f..248baae 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -39,6 +39,7 @@
#include <scsi/scsi.h>
#include "scsi.h"
#include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
#include <linux/libata.h>
#include <linux/hdreg.h>
#include <asm/uaccess.h>
@@ -2405,8 +2406,12 @@
struct ata_port *ap;
struct ata_device *dev;
struct scsi_device *scsidev = cmd->device;
+ struct Scsi_Host *shost = scsidev->host;
- ap = (struct ata_port *) &scsidev->host->hostdata[0];
+ ap = (struct ata_port *) &shost->hostdata[0];
+
+ spin_unlock(shost->host_lock);
+ spin_lock(&ap->host_set->lock);
ata_scsi_dump_cdb(ap, cmd);
@@ -2429,6 +2434,8 @@
ata_scsi_translate(ap, dev, cmd, done, atapi_xlat);
out_unlock:
+ spin_unlock(&ap->host_set->lock);
+ spin_lock(shost->host_lock);
return 0;
}