[v2,1/2] driver: core: add dedicated workqueue for devlink removal
Commit Message
From: Nuno Sa <nuno.sa@analog.com>
Let's use a dedicated queue for devlinks since releasing a link happens
asynchronously but some code paths, like DT overlays, have some
expectations regarding the of_node when being removed (the refcount must
be 1). Given how devlinks are released that cannot be assured. Hence, add a
dedicated queue so that it's easy to sync against devlinks removal.
While at it, make sure to explicitly include <linux/workqueue.h>.
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
---
drivers/base/core.c | 32 ++++++++++++++++++++++++++++----
include/linux/fwnode.h | 1 +
2 files changed, 29 insertions(+), 4 deletions(-)
Comments
On Mon, Feb 05, 2024 at 01:09:32PM +0100, Nuno Sa via B4 Relay wrote:
> From: Nuno Sa <nuno.sa@analog.com>
>
> Let's use a dedicated queue for devlinks since releasing a link happens
> asynchronously but some code paths, like DT overlays, have some
> expectations regarding the of_node when being removed (the refcount must
> be 1). Given how devlinks are released that cannot be assured. Hence, add a
> dedicated queue so that it's easy to sync against devlinks removal.
>
> While at it, make sure to explicitly include <linux/workqueue.h>.
..
> +++ b/include/linux/fwnode.h
> @@ -213,5 +213,6 @@ extern bool fw_devlink_is_strict(void);
> int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup);
> void fwnode_links_purge(struct fwnode_handle *fwnode);
> void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
> +void fwnode_links_flush_queue(void);
I am not sure if you have seen my comment against v1.
I find the namespace a bit messy for devlinks. And to me seems the best place
for this line is to be before fwnode_links_purge().
On Mon, Feb 5, 2024 at 1:09 PM Nuno Sa via B4 Relay
<devnull+nuno.sa.analog.com@kernel.org> wrote:
>
> From: Nuno Sa <nuno.sa@analog.com>
>
> Let's use a dedicated queue for devlinks since releasing a link happens
> asynchronously but some code paths, like DT overlays, have some
> expectations regarding the of_node when being removed (the refcount must
> be 1). Given how devlinks are released that cannot be assured. Hence, add a
> dedicated queue so that it's easy to sync against devlinks removal.
>
> While at it, make sure to explicitly include <linux/workqueue.h>.
>
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
> ---
> drivers/base/core.c | 32 ++++++++++++++++++++++++++++----
> include/linux/fwnode.h | 1 +
> 2 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 14d46af40f9a..4bb9c10489ed 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -31,6 +31,7 @@
> #include <linux/swiotlb.h>
> #include <linux/sysfs.h>
> #include <linux/dma-map-ops.h> /* for dma_default_coherent */
> +#include <linux/workqueue.h>
>
> #include "base.h"
> #include "physical_location.h"
> @@ -44,6 +45,7 @@ static bool fw_devlink_is_permissive(void);
> static void __fw_devlink_link_to_consumers(struct device *dev);
> static bool fw_devlink_drv_reg_done;
> static bool fw_devlink_best_effort;
> +static struct workqueue_struct *devlink_release_queue __ro_after_init;
>
> /**
> * __fwnode_link_add - Create a link between two fwnode_handles.
> @@ -235,6 +237,12 @@ static void __fw_devlink_pickup_dangling_consumers(struct fwnode_handle *fwnode,
> __fw_devlink_pickup_dangling_consumers(child, new_sup);
> }
>
> +void fwnode_links_flush_queue(void)
> +{
> + if (devlink_release_queue)
> + flush_workqueue(devlink_release_queue);
> +}
> +
> static DEFINE_MUTEX(device_links_lock);
> DEFINE_STATIC_SRCU(device_links_srcu);
>
> @@ -531,9 +539,13 @@ static void devlink_dev_release(struct device *dev)
> * It may take a while to complete this work because of the SRCU
> * synchronization in device_link_release_fn() and if the consumer or
> * supplier devices get deleted when it runs, so put it into the "long"
> - * workqueue.
> + * devlink workqueue (in case we could allocate one).
> + *
> */
> - queue_work(system_long_wq, &link->rm_work);
> + if (devlink_release_queue)
> + queue_work(devlink_release_queue, &link->rm_work);
> + else
> + device_link_release_fn(&link->rm_work);
> }
>
> static struct class devlink_class = {
> @@ -636,10 +648,22 @@ static int __init devlink_class_init(void)
> return ret;
>
> ret = class_interface_register(&devlink_class_intf);
> - if (ret)
> + if (ret) {
> class_unregister(&devlink_class);
> + return ret;
> + }
>
> - return ret;
> + /*
> + * Using a dedicated queue for devlinks since releasing a link happens
> + * asynchronously but some code paths, like DT overlays, have some
> + * expectations regarding the of_node when being removed (the refcount
> + * must be 1). Given how devlinks are released that cannot be assured.
> + * Hence, add a dedicated queue so that it's easy to sync against
> + * devlinks removal.
> + */
> + devlink_release_queue = alloc_workqueue("devlink_release", 0, 0);
> +
> + return 0;
> }
> postcore_initcall(devlink_class_init);
>
> diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
> index 2a72f55d26eb..017b170e9903 100644
> --- a/include/linux/fwnode.h
> +++ b/include/linux/fwnode.h
> @@ -213,5 +213,6 @@ extern bool fw_devlink_is_strict(void);
> int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup);
> void fwnode_links_purge(struct fwnode_handle *fwnode);
> void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
> +void fwnode_links_flush_queue(void);
>
> #endif
>
> --
> 2.43.0
>
On Mon, 2024-02-05 at 14:35 +0200, Andy Shevchenko wrote:
> On Mon, Feb 05, 2024 at 01:09:32PM +0100, Nuno Sa via B4 Relay wrote:
> > From: Nuno Sa <nuno.sa@analog.com>
> >
> > Let's use a dedicated queue for devlinks since releasing a link happens
> > asynchronously but some code paths, like DT overlays, have some
> > expectations regarding the of_node when being removed (the refcount must
> > be 1). Given how devlinks are released that cannot be assured. Hence, add a
> > dedicated queue so that it's easy to sync against devlinks removal.
> >
> > While at it, make sure to explicitly include <linux/workqueue.h>.
>
> ...
>
> > +++ b/include/linux/fwnode.h
> > @@ -213,5 +213,6 @@ extern bool fw_devlink_is_strict(void);
> > int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup);
> > void fwnode_links_purge(struct fwnode_handle *fwnode);
> > void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
> > +void fwnode_links_flush_queue(void);
>
> I am not sure if you have seen my comment against v1.
>
I did received it like 30min ago...
> I find the namespace a bit messy for devlinks. And to me seems the best place
> for this line is to be before fwnode_links_purge().
>
TBH, I'm not really keen on sending a v3 just for that (unless I'm asked otherwise).
But If I have (still missing DT guys feedback), I'll do as you suggested.
- Nuno Sá
@@ -31,6 +31,7 @@
#include <linux/swiotlb.h>
#include <linux/sysfs.h>
#include <linux/dma-map-ops.h> /* for dma_default_coherent */
+#include <linux/workqueue.h>
#include "base.h"
#include "physical_location.h"
@@ -44,6 +45,7 @@ static bool fw_devlink_is_permissive(void);
static void __fw_devlink_link_to_consumers(struct device *dev);
static bool fw_devlink_drv_reg_done;
static bool fw_devlink_best_effort;
+static struct workqueue_struct *devlink_release_queue __ro_after_init;
/**
* __fwnode_link_add - Create a link between two fwnode_handles.
@@ -235,6 +237,12 @@ static void __fw_devlink_pickup_dangling_consumers(struct fwnode_handle *fwnode,
__fw_devlink_pickup_dangling_consumers(child, new_sup);
}
+void fwnode_links_flush_queue(void)
+{
+ if (devlink_release_queue)
+ flush_workqueue(devlink_release_queue);
+}
+
static DEFINE_MUTEX(device_links_lock);
DEFINE_STATIC_SRCU(device_links_srcu);
@@ -531,9 +539,13 @@ static void devlink_dev_release(struct device *dev)
* It may take a while to complete this work because of the SRCU
* synchronization in device_link_release_fn() and if the consumer or
* supplier devices get deleted when it runs, so put it into the "long"
- * workqueue.
+ * devlink workqueue (in case we could allocate one).
+ *
*/
- queue_work(system_long_wq, &link->rm_work);
+ if (devlink_release_queue)
+ queue_work(devlink_release_queue, &link->rm_work);
+ else
+ device_link_release_fn(&link->rm_work);
}
static struct class devlink_class = {
@@ -636,10 +648,22 @@ static int __init devlink_class_init(void)
return ret;
ret = class_interface_register(&devlink_class_intf);
- if (ret)
+ if (ret) {
class_unregister(&devlink_class);
+ return ret;
+ }
- return ret;
+ /*
+ * Using a dedicated queue for devlinks since releasing a link happens
+ * asynchronously but some code paths, like DT overlays, have some
+ * expectations regarding the of_node when being removed (the refcount
+ * must be 1). Given how devlinks are released that cannot be assured.
+ * Hence, add a dedicated queue so that it's easy to sync against
+ * devlinks removal.
+ */
+ devlink_release_queue = alloc_workqueue("devlink_release", 0, 0);
+
+ return 0;
}
postcore_initcall(devlink_class_init);
@@ -213,5 +213,6 @@ extern bool fw_devlink_is_strict(void);
int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup);
void fwnode_links_purge(struct fwnode_handle *fwnode);
void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
+void fwnode_links_flush_queue(void);
#endif