[SCSI] Unlock accesses to eh_deadline

32bit accesses are guaranteed to be atomic, so we can remove
the spinlock when checking for eh_deadline. We only need to
make sure to catch any updates which might happened during
the call to time_before(); if so we just recheck with the
correct value.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 9 insertions, 35 deletions

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 3dd04026d466..4e4824beefe4 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -94,8 +94,15 @@ static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
         if (!shost->last_reset || !shost->eh_deadline)
                 return 0;
 
-        if (time_before(jiffies,
-                        shost->last_reset + shost->eh_deadline))
+        /*
+         * 32bit accesses are guaranteed to be atomic
+         * (on all supported architectures), so instead
+         * of using a spinlock we can as well double check
+         * if eh_deadline has been unset during the
+         * time_before call.
+         */
+        if (time_before(jiffies, shost->last_reset + shost->eh_deadline) &&
+            shost->eh_deadline != 0)
                 return 0;
 
         return 1;
@@ -111,18 +118,14 @@ scmd_eh_abort_handler(struct work_struct *work)
         struct scsi_cmnd *scmd =
                 container_of(work, struct scsi_cmnd, abort_work.work);
         struct scsi_device *sdev = scmd->device;
-        unsigned long flags;
         int rtn;
 
-        spin_lock_irqsave(sdev->host->host_lock, flags);
         if (scsi_host_eh_past_deadline(sdev->host)) {
-                spin_unlock_irqrestore(sdev->host->host_lock, flags);
                 SCSI_LOG_ERROR_RECOVERY(3,
                         scmd_printk(KERN_INFO, scmd,
                                     "scmd %p eh timeout, not aborting\n",
                                     scmd));
         } else {
-                spin_unlock_irqrestore(sdev->host->host_lock, flags);
                 SCSI_LOG_ERROR_RECOVERY(3,
                         scmd_printk(KERN_INFO, scmd,
                                     "aborting command %p\n", scmd));
@@ -1132,7 +1135,6 @@ int scsi_eh_get_sense(struct list_head *work_q,
         struct scsi_cmnd *scmd, *next;
         struct Scsi_Host *shost;
         int rtn;
-        unsigned long flags;
 
         list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
                 if ((scmd->eh_eflags & SCSI_EH_CANCEL_CMD) ||
@@ -1140,16 +1142,13 @@ int scsi_eh_get_sense(struct list_head *work_q,
                         continue;
 
                 shost = scmd->device->host;
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         SCSI_LOG_ERROR_RECOVERY(3,
                                 shost_printk(KERN_INFO, shost,
                                             "skip %s, past eh deadline\n",
                                              __func__));
                         break;
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
                 SCSI_LOG_ERROR_RECOVERY(2, scmd_printk(KERN_INFO, scmd,
                                                   "%s: requesting sense\n",
                                                   current->comm));
@@ -1235,26 +1234,21 @@ static int scsi_eh_test_devices(struct list_head *cmd_list,
         struct scsi_cmnd *scmd, *next;
         struct scsi_device *sdev;
         int finish_cmds;
-        unsigned long flags;
 
         while (!list_empty(cmd_list)) {
                 scmd = list_entry(cmd_list->next, struct scsi_cmnd, eh_entry);
                 sdev = scmd->device;
 
                 if (!try_stu) {
-                        spin_lock_irqsave(sdev->host->host_lock, flags);
                         if (scsi_host_eh_past_deadline(sdev->host)) {
                                 /* Push items back onto work_q */
                                 list_splice_init(cmd_list, work_q);
-                                spin_unlock_irqrestore(sdev->host->host_lock,
-                                                       flags);
                                 SCSI_LOG_ERROR_RECOVERY(3,
                                         shost_printk(KERN_INFO, sdev->host,
                                                      "skip %s, past eh deadline",
                                                      __func__));
                                 break;
                         }
-                        spin_unlock_irqrestore(sdev->host->host_lock, flags);
                 }
 
                 finish_cmds = !scsi_device_online(scmd->device) ||
@@ -1295,15 +1289,12 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
         LIST_HEAD(check_list);
         int rtn;
         struct Scsi_Host *shost;
-        unsigned long flags;
 
         list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
                 if (!(scmd->eh_eflags & SCSI_EH_CANCEL_CMD))
                         continue;
                 shost = scmd->device->host;
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         list_splice_init(&check_list, work_q);
                         SCSI_LOG_ERROR_RECOVERY(3,
                                 shost_printk(KERN_INFO, shost,
@@ -1311,7 +1302,6 @@ static int scsi_eh_abort_cmds(struct list_head *work_q,
                                              __func__));
                         return list_empty(work_q);
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
                 SCSI_LOG_ERROR_RECOVERY(3, printk("%s: aborting cmd:"
                                                   "0x%p\n", current->comm,
                                                   scmd));
@@ -1375,19 +1365,15 @@ static int scsi_eh_stu(struct Scsi_Host *shost,
 {
         struct scsi_cmnd *scmd, *stu_scmd, *next;
         struct scsi_device *sdev;
-        unsigned long flags;
 
         shost_for_each_device(sdev, shost) {
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         SCSI_LOG_ERROR_RECOVERY(3,
                                 shost_printk(KERN_INFO, shost,
                                             "skip %s, past eh deadline\n",
                                              __func__));
                         break;
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
                 stu_scmd = NULL;
                 list_for_each_entry(scmd, work_q, eh_entry)
                         if (scmd->device == sdev && SCSI_SENSE_VALID(scmd) &&
@@ -1441,20 +1427,16 @@ static int scsi_eh_bus_device_reset(struct Scsi_Host *shost,
 {
         struct scsi_cmnd *scmd, *bdr_scmd, *next;
         struct scsi_device *sdev;
-        unsigned long flags;
         int rtn;
 
         shost_for_each_device(sdev, shost) {
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         SCSI_LOG_ERROR_RECOVERY(3,
                                 shost_printk(KERN_INFO, shost,
                                             "skip %s, past eh deadline\n",
                                              __func__));
                         break;
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
                 bdr_scmd = NULL;
                 list_for_each_entry(scmd, work_q, eh_entry)
                         if (scmd->device == sdev) {
@@ -1515,11 +1497,8 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
                 struct scsi_cmnd *next, *scmd;
                 int rtn;
                 unsigned int id;
-                unsigned long flags;
 
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         /* push back on work queue for further processing */
                         list_splice_init(&check_list, work_q);
                         list_splice_init(&tmp_list, work_q);
@@ -1529,7 +1508,6 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
                                              __func__));
                         return list_empty(work_q);
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
 
                 scmd = list_entry(tmp_list.next, struct scsi_cmnd, eh_entry);
                 id = scmd_id(scmd);
@@ -1574,7 +1552,6 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
         LIST_HEAD(check_list);
         unsigned int channel;
         int rtn;
-        unsigned long flags;
 
         /*
          * we really want to loop over the various channels, and do this on
@@ -1584,9 +1561,7 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
          */
 
         for (channel = 0; channel <= shost->max_channel; channel++) {
-                spin_lock_irqsave(shost->host_lock, flags);
                 if (scsi_host_eh_past_deadline(shost)) {
-                        spin_unlock_irqrestore(shost->host_lock, flags);
                         list_splice_init(&check_list, work_q);
                         SCSI_LOG_ERROR_RECOVERY(3,
                                 shost_printk(KERN_INFO, shost,
@@ -1594,7 +1569,6 @@ static int scsi_eh_bus_reset(struct Scsi_Host *shost,
                                              __func__));
                         return list_empty(work_q);
                 }
-                spin_unlock_irqrestore(shost->host_lock, flags);
 
                 chan_scmd = NULL;
                 list_for_each_entry(scmd, work_q, eh_entry) {