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From:   John Garry <john.g.garry@oracle.com>
To:     jejb@linux.ibm.com, martin.petersen@oracle.com,
        dgilbert@interlog.com
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        bvanassche@acm.org, John Garry <john.g.garry@oracle.com>
Subject: [PATCH v3 03/11] scsi: scsi_debug: Change shost list lock to a mutex
Date:   Mon, 27 Mar 2023 07:43:02 +0000
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The shost list lock, sdebug_host_list_lock, is a spinlock. We would only
lock in non-atomic context in this driver, so use a mutex instead, which
is friendlier if we need to schedule when iterating.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
 drivers/scsi/scsi_debug.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index eba6eca81e84..a61e7c31dab5 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -816,7 +816,7 @@ static int sdebug_cylinders_per;	/* cylinders per surface */
 static int sdebug_sectors_per;		/* sectors per cylinder */
 
 static LIST_HEAD(sdebug_host_list);
-static DEFINE_SPINLOCK(sdebug_host_list_lock);
+static DEFINE_MUTEX(sdebug_host_list_mutex);
 
 static struct xarray per_store_arr;
 static struct xarray *per_store_ap = &per_store_arr;
@@ -908,7 +908,7 @@ static void sdebug_max_tgts_luns(void)
 	struct sdebug_host_info *sdbg_host;
 	struct Scsi_Host *hpnt;
 
-	spin_lock(&sdebug_host_list_lock);
+	mutex_lock(&sdebug_host_list_mutex);
 	list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
 		hpnt = sdbg_host->shost;
 		if ((hpnt->this_id >= 0) &&
@@ -919,7 +919,7 @@ static void sdebug_max_tgts_luns(void)
 		/* sdebug_max_luns; */
 		hpnt->max_lun = SCSI_W_LUN_REPORT_LUNS + 1;
 	}
-	spin_unlock(&sdebug_host_list_lock);
+	mutex_unlock(&sdebug_host_list_mutex);
 }
 
 enum sdeb_cmd_data {SDEB_IN_DATA = 0, SDEB_IN_CDB = 1};
@@ -1051,14 +1051,14 @@ static void all_config_cdb_len(void)
 	struct Scsi_Host *shost;
 	struct scsi_device *sdev;
 
-	spin_lock(&sdebug_host_list_lock);
+	mutex_lock(&sdebug_host_list_mutex);
 	list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
 		shost = sdbg_host->shost;
 		shost_for_each_device(sdev, shost) {
 			config_cdb_len(sdev);
 		}
 	}
-	spin_unlock(&sdebug_host_list_lock);
+	mutex_unlock(&sdebug_host_list_mutex);
 }
 
 static void clear_luns_changed_on_target(struct sdebug_dev_info *devip)
@@ -5423,7 +5423,7 @@ static int scsi_debug_host_reset(struct scsi_cmnd *SCpnt)
 	++num_host_resets;
 	if (SDEBUG_OPT_ALL_NOISE & sdebug_opts)
 		sdev_printk(KERN_INFO, SCpnt->device, "%s\n", __func__);
-	spin_lock(&sdebug_host_list_lock);
+	mutex_lock(&sdebug_host_list_mutex);
 	list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
 		list_for_each_entry(devip, &sdbg_host->dev_info_list,
 				    dev_list) {
@@ -5431,7 +5431,7 @@ static int scsi_debug_host_reset(struct scsi_cmnd *SCpnt)
 			++k;
 		}
 	}
-	spin_unlock(&sdebug_host_list_lock);
+	mutex_unlock(&sdebug_host_list_mutex);
 	stop_all_queued();
 	if (SDEBUG_OPT_RESET_NOISE & sdebug_opts)
 		sdev_printk(KERN_INFO, SCpnt->device,
@@ -6337,13 +6337,13 @@ static ssize_t lun_format_store(struct device_driver *ddp, const char *buf,
 			struct sdebug_host_info *sdhp;
 			struct sdebug_dev_info *dp;
 
-			spin_lock(&sdebug_host_list_lock);
+			mutex_lock(&sdebug_host_list_mutex);
 			list_for_each_entry(sdhp, &sdebug_host_list, host_list) {
 				list_for_each_entry(dp, &sdhp->dev_info_list, dev_list) {
 					set_bit(SDEBUG_UA_LUNS_CHANGED, dp->uas_bm);
 				}
 			}
-			spin_unlock(&sdebug_host_list_lock);
+			mutex_unlock(&sdebug_host_list_mutex);
 		}
 		return count;
 	}
@@ -6373,7 +6373,7 @@ static ssize_t max_luns_store(struct device_driver *ddp, const char *buf,
 			struct sdebug_host_info *sdhp;
 			struct sdebug_dev_info *dp;
 
-			spin_lock(&sdebug_host_list_lock);
+			mutex_lock(&sdebug_host_list_mutex);
 			list_for_each_entry(sdhp, &sdebug_host_list,
 					    host_list) {
 				list_for_each_entry(dp, &sdhp->dev_info_list,
@@ -6382,7 +6382,7 @@ static ssize_t max_luns_store(struct device_driver *ddp, const char *buf,
 						dp->uas_bm);
 				}
 			}
-			spin_unlock(&sdebug_host_list_lock);
+			mutex_unlock(&sdebug_host_list_mutex);
 		}
 		return count;
 	}
@@ -6489,7 +6489,7 @@ static ssize_t virtual_gb_store(struct device_driver *ddp, const char *buf,
 			struct sdebug_host_info *sdhp;
 			struct sdebug_dev_info *dp;
 
-			spin_lock(&sdebug_host_list_lock);
+			mutex_lock(&sdebug_host_list_mutex);
 			list_for_each_entry(sdhp, &sdebug_host_list,
 					    host_list) {
 				list_for_each_entry(dp, &sdhp->dev_info_list,
@@ -6498,7 +6498,7 @@ static ssize_t virtual_gb_store(struct device_driver *ddp, const char *buf,
 						dp->uas_bm);
 				}
 			}
-			spin_unlock(&sdebug_host_list_lock);
+			mutex_unlock(&sdebug_host_list_mutex);
 		}
 		return count;
 	}
@@ -7258,9 +7258,9 @@ static int sdebug_add_host_helper(int per_host_idx)
 			goto clean;
 	}
 
-	spin_lock(&sdebug_host_list_lock);
+	mutex_lock(&sdebug_host_list_mutex);
 	list_add_tail(&sdbg_host->host_list, &sdebug_host_list);
-	spin_unlock(&sdebug_host_list_lock);
+	mutex_unlock(&sdebug_host_list_mutex);
 
 	sdbg_host->dev.bus = &pseudo_lld_bus;
 	sdbg_host->dev.parent = pseudo_primary;
@@ -7269,9 +7269,9 @@ static int sdebug_add_host_helper(int per_host_idx)
 
 	error = device_register(&sdbg_host->dev);
 	if (error) {
-		spin_lock(&sdebug_host_list_lock);
+		mutex_lock(&sdebug_host_list_mutex);
 		list_del(&sdbg_host->host_list);
-		spin_unlock(&sdebug_host_list_lock);
+		mutex_unlock(&sdebug_host_list_mutex);
 		goto clean;
 	}
 
@@ -7311,7 +7311,7 @@ static void sdebug_do_remove_host(bool the_end)
 	struct sdebug_host_info *sdbg_host = NULL;
 	struct sdebug_host_info *sdbg_host2;
 
-	spin_lock(&sdebug_host_list_lock);
+	mutex_lock(&sdebug_host_list_mutex);
 	if (!list_empty(&sdebug_host_list)) {
 		sdbg_host = list_entry(sdebug_host_list.prev,
 				       struct sdebug_host_info, host_list);
@@ -7336,7 +7336,7 @@ static void sdebug_do_remove_host(bool the_end)
 	}
 	if (sdbg_host)
 		list_del(&sdbg_host->host_list);
-	spin_unlock(&sdebug_host_list_lock);
+	mutex_unlock(&sdebug_host_list_mutex);
 
 	if (!sdbg_host)
 		return;
-- 
2.35.3