Extend the workqueue API so that singlethread workqueues can be exposed
in sysfs. Guarantee max_active is 1 by turning it read-only.
This allows admins to control the cpumask of a workqueue, and apply
the desired system cpu separation/isolation policy.
Signed-off-by: Tariq Toukan <tar...@nvidia.com>
---
drivers/net/ethernet/mellanox/mlx5/core/cmd.c | 2 +-
include/linux/workqueue.h | 4 ++++
kernel/workqueue.c | 21 +++++++++++++++++--
3 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
index 1d91a0d0ab1d..5106820a5cd5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
@@ -2033,7 +2033,7 @@ int mlx5_cmd_init(struct mlx5_core_dev *dev)
create_msg_cache(dev);
set_wqname(dev);
- cmd->wq = create_singlethread_workqueue(cmd->wq_name);
+ cmd->wq = create_singlethread_sysfs_workqueue(cmd->wq_name);
if (!cmd->wq) {
mlx5_core_err(dev, "failed to create command workqueue\n");
err = -ENOMEM;
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 26de0cae2a0a..d4d4ca2b041a 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -344,6 +344,7 @@ enum {
__WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
__WQ_LEGACY = 1 << 18, /* internal: create*_workqueue() */
__WQ_ORDERED_EXPLICIT = 1 << 19, /* internal:
alloc_ordered_workqueue() */
+ __WQ_MAX_ACTIVE_RO = 1 << 20, /* internal: make max_active
read-only */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
@@ -432,6 +433,9 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
WQ_MEM_RECLAIM, 1, (name))
#define create_singlethread_workqueue(name) \
alloc_ordered_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)
+#define create_singlethread_sysfs_workqueue(name) \
+ alloc_ordered_workqueue("%s", __WQ_MAX_ACTIVE_RO | \
+ __WQ_LEGACY | WQ_MEM_RECLAIM, name)
extern void destroy_workqueue(struct workqueue_struct *wq);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c41c3c17b86a..a80d34726e68 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4258,6 +4258,9 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
flags |= WQ_UNBOUND;
+ if (flags & __WQ_MAX_ACTIVE_RO)
+ flags |= WQ_SYSFS;
+
/* allocate wq and format name */
if (flags & WQ_UNBOUND)
tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
@@ -5401,9 +5404,11 @@ static ssize_t max_active_store(struct device *dev,
}
static DEVICE_ATTR_RW(max_active);
+static struct device_attribute dev_attr_max_active_ro =
+ __ATTR(max_active, 0444, max_active_show, NULL);
+
static struct attribute *wq_sysfs_attrs[] = {
&dev_attr_per_cpu.attr,
- &dev_attr_max_active.attr,
NULL,
};
ATTRIBUTE_GROUPS(wq_sysfs);
@@ -5642,6 +5647,7 @@ static void wq_device_release(struct device *dev)
*/
int workqueue_sysfs_register(struct workqueue_struct *wq)
{
+ const struct device_attribute *max_active_entry;
struct wq_device *wq_dev;
int ret;
@@ -5650,7 +5656,8 @@ int workqueue_sysfs_register(struct workqueue_struct *wq)
* attributes breaks ordering guarantee. Disallow exposing ordered
* workqueues.
*/
- if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
+ if (WARN_ON(!(wq->flags & __WQ_MAX_ACTIVE_RO) &&
+ wq->flags & __WQ_ORDERED_EXPLICIT))
return -EINVAL;
wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
@@ -5675,6 +5682,16 @@ int workqueue_sysfs_register(struct workqueue_struct *wq)
return ret;
}
+ max_active_entry = wq->flags & __WQ_MAX_ACTIVE_RO ?
+ &dev_attr_max_active_ro : &dev_attr_max_active;
+
+ ret = device_create_file(&wq_dev->dev, max_active_entry);
+ if (ret) {
+ device_unregister(&wq_dev->dev);
+ wq->wq_dev = NULL;
+ return ret;
+ }
+
if (wq->flags & WQ_UNBOUND) {
struct device_attribute *attr;
--
2.21.0
