@@ -104,14 +104,11 @@ static ssize_t target_type_show(struct device *dev,
}
static DEVICE_ATTR_RO(target_type);
-static ssize_t target_list_show(struct device *dev,
- struct device_attribute *attr, char *buf)
+static ssize_t emit_target_list(struct cxl_decoder *cxld, char *buf)
{
- struct cxl_decoder *cxld = to_cxl_decoder(dev);
ssize_t offset = 0;
int i, rc = 0;
- cxl_device_lock(dev);
for (i = 0; i < cxld->interleave_ways; i++) {
struct cxl_dport *dport = cxld->target[i];
struct cxl_dport *next = NULL;
@@ -127,10 +124,28 @@ static ssize_t target_list_show(struct device *dev,
break;
offset += rc;
}
- cxl_device_unlock(dev);
if (rc < 0)
return rc;
+ return offset;
+}
+
+static ssize_t target_list_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct cxl_decoder *cxld = to_cxl_decoder(dev);
+ ssize_t offset;
+ unsigned int seq;
+ int rc;
+
+ do {
+ seq = read_seqbegin(&cxld->target_lock);
+ rc = emit_target_list(cxld, buf);
+ } while (read_seqretry(&cxld->target_lock, seq));
+
+ if (rc < 0)
+ return rc;
+ offset = rc;
rc = sysfs_emit_at(buf, offset, "\n");
if (rc < 0)
@@ -494,6 +509,7 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
goto out_unlock;
}
+ write_seqlock(&cxld->target_lock);
for (i = 0; i < cxld->nr_targets; i++) {
struct cxl_dport *dport = find_dport(port, target_map[i]);
@@ -503,6 +519,7 @@ static int decoder_populate_targets(struct cxl_decoder *cxld,
}
cxld->target[i] = dport;
}
+ write_sequnlock(&cxld->target_lock);
out_unlock:
cxl_device_unlock(&port->dev);
@@ -543,6 +560,7 @@ static struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port,
cxld->id = rc;
cxld->nr_targets = nr_targets;
+ seqlock_init(&cxld->target_lock);
dev = &cxld->dev;
device_initialize(dev);
device_set_pm_not_required(dev);
@@ -185,6 +185,7 @@ enum cxl_decoder_type {
* @interleave_granularity: data stride per dport
* @target_type: accelerator vs expander (type2 vs type3) selector
* @flags: memory type capabilities and locking
+ * @target_lock: coordinate coherent reads of the target list
* @nr_targets: number of elements in @target
* @target: active ordered target list in current decoder configuration
*/
@@ -199,6 +200,7 @@ struct cxl_decoder {
int interleave_granularity;
enum cxl_decoder_type target_type;
unsigned long flags;
+ seqlock_t target_lock;
int nr_targets;
struct cxl_dport *target[];
};
Lockdep reports: ====================================================== WARNING: possible circular locking dependency detected 5.16.0-rc1+ #142 Tainted: G OE ------------------------------------------------------ cxl/1220 is trying to acquire lock: ffff979b85475460 (kn->active#144){++++}-{0:0}, at: __kernfs_remove+0x1ab/0x1e0 but task is already holding lock: ffff979b87ab38e8 (&dev->lockdep_mutex#2/4){+.+.}-{3:3}, at: cxl_remove_ep+0x50c/0x5c0 [cxl_core] ...where cxl_remove_ep() is a helper that wants to delete ports while holding a lock on the host device for that port. That sets up a lockdep violation whereby target_list_show() can not rely holding the decoder's device lock while walking the target_list. Switch to a dedicated seqlock for this purpose. Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- drivers/cxl/core/port.c | 28 +++++++++++++++++++++++----- drivers/cxl/cxl.h | 2 ++ 2 files changed, 25 insertions(+), 5 deletions(-)