diff mbox series

[v2,1/2] driver: core: add dedicated workqueue for devlink removal

Message ID 20240205-fix-device-links-overlays-v2-1-5344f8c79d57@analog.com (mailing list archive)
State Handled Elsewhere, archived
Headers show
Series fix DT overlays when device links are released | expand

Commit Message

Nuno Sa via B4 Relay Feb. 5, 2024, 12:09 p.m. UTC 
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

Rafael J. Wysocki Feb. 5, 2024, 1:37 p.m. UTC | #1 
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
>
Nuno Sá Feb. 5, 2024, 2:32 p.m. UTC | #2 
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
diff mbox series

Patch

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