[PATCH v3 04/11] scsi: scsi_debug: Protect block_unblock_all_queues() with mutex

John Garry
2023-03-27T07:44:03Z

There is no reason that calls to block_unblock_all_queues() from different
context can't race with one another, so protect with the
sdebug_host_list_mutex. There's no need for a more fine-grained per shost
locking here (and we don't have a per-host lock anyway).

Also simplify some touched code in sdebug_change_qdepth().

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
drivers/scsi/scsi_debug.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index a61e7c31dab5..cd05e2f87417 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5497,6 +5497,8 @@ static void block_unblock_all_queues(bool block)
int j;
struct sdebug_queue *sqp;

+ lockdep_assert_held(&sdebug_host_list_mutex);
+
for (j = 0, sqp = sdebug_q_arr; j < submit_queues; ++j, ++sqp)
atomic_set(&sqp->blocked, (int)block);
}
@@ -5511,10 +5513,13 @@ static void tweak_cmnd_count(void)
modulo = abs(sdebug_every_nth);
if (modulo < 2)
return;
+
+ mutex_lock(&sdebug_host_list_mutex);
block_unblock_all_queues(true);
count = atomic_read(&sdebug_cmnd_count);
atomic_set(&sdebug_cmnd_count, (count / modulo) * modulo);
block_unblock_all_queues(false);
+ mutex_unlock(&sdebug_host_list_mutex);
}

static void clear_queue_stats(void)
@@ -6036,6 +6041,7 @@ static ssize_t delay_store(struct device_driver *ddp, const char *buf,
int j, k;
struct sdebug_queue *sqp;

+ mutex_lock(&sdebug_host_list_mutex);
block_unblock_all_queues(true);
for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
++j, ++sqp) {
@@ -6051,6 +6057,7 @@ static ssize_t delay_store(struct device_driver *ddp, const char *buf,
sdebug_ndelay = 0;
}
block_unblock_all_queues(false);
+ mutex_unlock(&sdebug_host_list_mutex);
}
return res;
}
@@ -6076,6 +6083,7 @@ static ssize_t ndelay_store(struct device_driver *ddp, const char *buf,
int j, k;
struct sdebug_queue *sqp;

+ mutex_lock(&sdebug_host_list_mutex);
block_unblock_all_queues(true);
for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
++j, ++sqp) {
@@ -6092,6 +6100,7 @@ static ssize_t ndelay_store(struct device_driver *ddp, const char *buf,
: DEF_JDELAY;
}
block_unblock_all_queues(false);
+ mutex_unlock(&sdebug_host_list_mutex);
}
return res;
}
@@ -6405,6 +6414,7 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n > 0) &&
(n <= SDEBUG_CANQUEUE) &&
(sdebug_host_max_queue == 0)) {
+ mutex_lock(&sdebug_host_list_mutex);
block_unblock_all_queues(true);
k = 0;
for (j = 0, sqp = sdebug_q_arr; j < submit_queues;
@@ -6421,6 +6431,7 @@ static ssize_t max_queue_store(struct device_driver *ddp, const char *buf,
else
atomic_set(&retired_max_queue, 0);
block_unblock_all_queues(false);
+ mutex_unlock(&sdebug_host_list_mutex);
return count;
}
return -EINVAL;
@@ -7352,7 +7363,9 @@ static int sdebug_change_qdepth(struct scsi_device *sdev, int qdepth)
if (!devip)
return -ENODEV;

+ mutex_lock(&sdebug_host_list_mutex);
block_unblock_all_queues(true);
+
if (qdepth > SDEBUG_CANQUEUE) {
qdepth = SDEBUG_CANQUEUE;
pr_warn("%s: requested qdepth [%d] exceeds canqueue [%d], trim\n", __func__,
@@ -7363,9 +7376,12 @@ static int sdebug_change_qdepth(struct scsi_device *sdev, int qdepth)
if (qdepth != sdev->queue_depth)
scsi_change_queue_depth(sdev, qdepth);

+ block_unblock_all_queues(false);
+ mutex_unlock(&sdebug_host_list_mutex);
+
if (SDEBUG_OPT_Q_NOISE & sdebug_opts)
sdev_printk(KERN_INFO, sdev, "%s: qdepth=%d\n", __func__, qdepth);
- block_unblock_all_queues(false);
+
return sdev->queue_depth;
}

--
2.35.3