driver core: fw_devlink: Stop trying to optimize cycle detection logic

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

---
 drivers/base/core.c | 55 ++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 31 deletions(-)

Tomi,

Thanks for all the testing and debugging help! And do use post-init-providers even with this patch to improve ordering enforcement. I probably should change the cycle log from info to warn in a separate patch :)

Greg,

I no longer have concerns about pulling this into 6.13. But we can give a week or so to Geert/Francesco to do some additional testing.

Geert/Francesco,

If you want to test this patch, pull it in and compare the output of the following:

ls -1 /sys/class/devlink

The only device links that should be missing with the patch should be device links in a cycle that weren't detected before.

Also, if you notice any significant boot time increase with this change, let me know.

Thanks,
Saravana

drivers/base/core.c +24 -32

index 3b13fed1c3e3..9a490b1b7a6f 100644
@@ -1990,10 +1990,10 @@ static struct device *fwnode_get_next_parent_dev(const struct fwnode_handle *fwn
  *
  * Return true if one or more cycles were found. Otherwise, return false.
  */
-static bool __fw_devlink_relax_cycles(struct device *con,
+static bool __fw_devlink_relax_cycles(struct fwnode_handle *con_handle,
                                 struct fwnode_handle *sup_handle)
 {
-       struct device *sup_dev = NULL, *par_dev = NULL;
+       struct device *sup_dev = NULL, *par_dev = NULL, *con_dev = NULL;
        struct fwnode_link *link;
        struct device_link *dev_link;
        bool ret = false;

@@ -2010,22 +2010,22 @@ static bool __fw_devlink_relax_cycles(struct device *con,
 
        sup_handle->flags |= FWNODE_FLAG_VISITED;
 
-       sup_dev = get_dev_from_fwnode(sup_handle);
-
        /* Termination condition. */
-       if (sup_dev == con) {
+       if (sup_handle == con_handle) {
                pr_debug("----- cycle: start -----\n");
                ret = true;
                goto out;
        }
 
+       sup_dev = get_dev_from_fwnode(sup_handle);
+       con_dev = get_dev_from_fwnode(con_handle);
        /*
         * If sup_dev is bound to a driver and @con hasn't started binding to a
         * driver, sup_dev can't be a consumer of @con. So, no need to check
         * further.
         */
        if (sup_dev && sup_dev->links.status ==  DL_DEV_DRIVER_BOUND &&
-           con->links.status == DL_DEV_NO_DRIVER) {
+           con_dev && con_dev->links.status == DL_DEV_NO_DRIVER) {
                ret = false;
                goto out;
        }

@@ -2034,7 +2034,7 @@ static bool __fw_devlink_relax_cycles(struct device *con,
                if (link->flags & FWLINK_FLAG_IGNORE)
                        continue;
 
-               if (__fw_devlink_relax_cycles(con, link->supplier)) {
+               if (__fw_devlink_relax_cycles(con_handle, link->supplier)) {
                        __fwnode_link_cycle(link);
                        ret = true;
                }

@@ -2049,7 +2049,7 @@ static bool __fw_devlink_relax_cycles(struct device *con,
        else
                par_dev = fwnode_get_next_parent_dev(sup_handle);
 
-       if (par_dev && __fw_devlink_relax_cycles(con, par_dev->fwnode)) {
+       if (par_dev && __fw_devlink_relax_cycles(con_handle, par_dev->fwnode)) {
                pr_debug("%pfwf: cycle: child of %pfwf\n", sup_handle,
                         par_dev->fwnode);
                ret = true;

@@ -2067,7 +2067,7 @@ static bool __fw_devlink_relax_cycles(struct device *con,
                    !(dev_link->flags & DL_FLAG_CYCLE))
                        continue;
 
-               if (__fw_devlink_relax_cycles(con,
+               if (__fw_devlink_relax_cycles(con_handle,
                                              dev_link->supplier->fwnode)) {
                        pr_debug("%pfwf: cycle: depends on %pfwf\n", sup_handle,
                                 dev_link->supplier->fwnode);

@@ -2115,11 +2115,6 @@ static int fw_devlink_create_devlink(struct device *con,
        if (link->flags & FWLINK_FLAG_IGNORE)
                return 0;
 
-       if (con->fwnode == link->consumer)
-               flags = fw_devlink_get_flags(link->flags);
-       else
-               flags = FW_DEVLINK_FLAGS_PERMISSIVE;
-
        /*
         * In some cases, a device P might also be a supplier to its child node
         * C. However, this would defer the probe of C until the probe of P

@@ -2140,25 +2135,23 @@ static int fw_devlink_create_devlink(struct device *con,
                return -EINVAL;
 
        /*
-        * SYNC_STATE_ONLY device links don't block probing and supports cycles.
-        * So, one might expect that cycle detection isn't necessary for them.
-        * However, if the device link was marked as SYNC_STATE_ONLY because
-        * it's part of a cycle, then we still need to do cycle detection. This
-        * is because the consumer and supplier might be part of multiple cycles
-        * and we need to detect all those cycles.
+        * Don't try to optimize by not calling the cycle detection logic under
+        * certain conditions. There's always some corner case that won't get
+        * detected.
         */
-       if (!device_link_flag_is_sync_state_only(flags) ||
-           flags & DL_FLAG_CYCLE) {
-               device_links_write_lock();
-               if (__fw_devlink_relax_cycles(con, sup_handle)) {
-                       __fwnode_link_cycle(link);
-                       flags = fw_devlink_get_flags(link->flags);
-                       pr_debug("----- cycle: end -----\n");
-                       dev_info(con, "Fixed dependency cycle(s) with %pfwf\n",
-                                sup_handle);
-               }
-               device_links_write_unlock();
+       device_links_write_lock();
+       if (__fw_devlink_relax_cycles(link->consumer, sup_handle)) {
+               __fwnode_link_cycle(link);
+               pr_debug("----- cycle: end -----\n");
+               pr_info("%pfwf: Fixed dependency cycle(s) with %pfwf\n",
+                       link->consumer, sup_handle);
        }
+       device_links_write_unlock();
+
+       if (con->fwnode == link->consumer)
+               flags = fw_devlink_get_flags(link->flags);
+       else
+               flags = FW_DEVLINK_FLAGS_PERMISSIVE;
 
        if (sup_handle->flags & FWNODE_FLAG_NOT_DEVICE)
                sup_dev = fwnode_get_next_parent_dev(sup_handle);
--

2.47.0.163.g1226f6d8fa-goog

Quoted 41 lines · Saravana Kannan

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

---
 drivers/base/core.c | 55 ++++++++++++++++++++-------------------------
 1 file changed, 24 insertions(+), 31 deletions(-)

Tomi,

Thanks for all the testing and debugging help! And do use post-init-providers even with this patch to improve ordering enforcement. I probably should change the cycle log from info to warn in a separate patch :)

Greg,

I no longer have concerns about pulling this into 6.13. But we can give a week or so to Geert/Francesco to do some additional testing.

Quoted 1 line

Geert/Francesco,

Heads up. Greg has pulled this into driver-core git's driver-core-testing branch. Which means in a week or two it'll get into the actual driver-core-next branch. So, if you want to do additional testing, you might want to jump on it soon.

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

Geert/Francesco,

If you want to test this patch, pull it in and compare the output of the following:

ls -1 /sys/class/devlink

The only device links that should be missing with the patch should be device links in a cycle that weren't detected before.

Hi Saravana,

Quoted 19 lines · Saravana Kannan

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Quoted 5 lines

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

Thanks for your patch, which is now commit bac3b10b78e54b7d ("driver
core: fw_devlink: Stop trying to optimize cycle detection logic") in next-20241107 and later.

Quoted 5 lines

Geert/Francesco,

If you want to test this patch, pull it in and compare the output of the following:

Quoted 4 lines

ls -1 /sys/class/devlink

The only device links that should be missing with the patch should be device links in a cycle that weren't detected before.

I gave it a try on all my boards, and compared the output on a few of them, and everything looks fine.

Quoted 40 lines · Geert Uytterhoeven

Quoted 19 lines · Saravana Kannan

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Quoted 5 lines

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

Thanks for your patch, which is now commit bac3b10b78e54b7d ("driver
core: fw_devlink: Stop trying to optimize cycle detection logic") in next-20241107 and later.

Quoted 9 lines

Geert/Francesco,

If you want to test this patch, pull it in and compare the output of the following:

ls -1 /sys/class/devlink

The only device links that should be missing with the patch should be device links in a cycle that weren't detected before.

Quoted 2 lines

I gave it a try on all my boards, and compared the output on a few of them, and everything looks fine.

Thanks for testing the series Geert!

And no noticeable boot time increases?

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

Quoted 19 lines · On Wed, 30 Oct 2024 10:10:07 -0700 Saravana Kannan <[email protected]> wrote:

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Quoted 5 lines

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

After rebasing my work for the hotplug connector driver using device tree overlays [0] on v6.13-rc1 I started getting these OF errors on overlay removal:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys

...and many more. Exactly one per each device in the overlay 'devices' node, each implemented by a platform driver.

Hi Luca,

Quoted 38 lines · Luca Ceresoli

Quoted 19 lines · On Wed, 30 Oct 2024 10:10:07 -0700 Saravana Kannan <[email protected]> wrote:

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Quoted 5 lines

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

After rebasing my work for the hotplug connector driver using device tree overlays [0] on v6.13-rc1 I started getting these OF errors on overlay removal:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys

Quoted 2 lines

...and many more. Exactly one per each device in the overlay 'devices' node, each implemented by a platform driver.

FTR, I am not seeing that when loading/removing
r8a77990-ebisu-cn41-msiof0-25lc040.dtso
https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/commit/?h=topic/renesas-overlays&id=dd998e8db58b67744eb91f11f13544401c975470

Hello Saravana,

+Cc. DT maintainers, Hervé

Quoted 19 lines · On Wed, 30 Oct 2024 10:10:07 -0700 Saravana Kannan <[email protected]> wrote:

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Quoted 5 lines

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

After rebasing my work for the hotplug connector driver using device tree overlays [0] on v6.13-rc1 I started getting these OF errors on overlay removal:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys

...and many more. Exactly one per each device in the overlay 'devices' node, each implemented by a platform driver.

Bisecting found this patch is triggering these error messages, which in fact disappear by reverting it.

I looked at the differences in dmesg and /sys/class/devlink/ in the "good" and "bad" cases, and found almost no differences. The only relevant difference is in cycle detection for the panel node, which was expected, but nothing about all the other nodes like regulators.

Enabling debug messages in core.c also does not show significant changes between the two cases, even though it's hard to be sure given the verbosity of the log and the reordering of messages.

I suspect the new version of the cycle removal code is missing an of_node_get() somewhere, but that is not directly visible in the patch diff itself.

Quoted 21 lines

After rebasing my work for the hotplug connector driver using device tree overlays [0] on v6.13-rc1 I started getting these OF errors on overlay removal:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys

...and many more. Exactly one per each device in the overlay 'devices' node, each implemented by a platform driver.

Bisecting found this patch is triggering these error messages, which in fact disappear by reverting it.

I looked at the differences in dmesg and /sys/class/devlink/ in the "good" and "bad" cases, and found almost no differences. The only relevant difference is in cycle detection for the panel node, which was expected, but nothing about all the other nodes like regulators.

Quoted 7 lines

Enabling debug messages in core.c also does not show significant changes between the two cases, even though it's hard to be sure given the verbosity of the log and the reordering of messages.

I suspect the new version of the cycle removal code is missing an of_node_get() somewhere, but that is not directly visible in the patch diff itself.

I collected some more info by adding a bit of logging for one of the affected devices.

It looks like the of_node_get() and of_node_put() in the overlay loading phase are the same, even though not completely in the same order. So after overlay insertion we should have the same refcount with and without your patch.

There is a difference on overlay removal however: an of_node_put() call is absent with 6.13-rc1 code (errors emitted), and becomes present by just reverting your patch (the "good" case). Here's the stack trace of this call:

 Call trace:
  show_stack+0x20/0x38 (C)
  dump_stack_lvl+0x74/0x90
  dump_stack+0x18/0x28
  of_node_put+0x50/0x70
  platform_device_release+0x24/0x68
  device_release+0x3c/0xa0
  kobject_put+0xa4/0x118
  device_link_release_fn+0x60/0xd8
  process_one_work+0x158/0x3c0
  worker_thread+0x2d8/0x3e8
  kthread+0x118/0x128
  ret_from_fork+0x10/0x20

So for some reason device_link_release_fn() is not leading to a of_node_put() call after adding your patch.

Quick code inspection did not show any useful info for me to understand more.

Hello,

Quoted 56 lines · On Fri, 6 Dec 2024 10:31:43 +0100 Luca Ceresoli <[email protected]>…

Quoted 21 lines

After rebasing my work for the hotplug connector driver using device tree overlays [0] on v6.13-rc1 I started getting these OF errors on overlay removal:

OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys

...and many more. Exactly one per each device in the overlay 'devices' node, each implemented by a platform driver.

Bisecting found this patch is triggering these error messages, which in fact disappear by reverting it.

I looked at the differences in dmesg and /sys/class/devlink/ in the "good" and "bad" cases, and found almost no differences. The only relevant difference is in cycle detection for the panel node, which was expected, but nothing about all the other nodes like regulators.

Quoted 7 lines

Enabling debug messages in core.c also does not show significant changes between the two cases, even though it's hard to be sure given the verbosity of the log and the reordering of messages.

I suspect the new version of the cycle removal code is missing an of_node_get() somewhere, but that is not directly visible in the patch diff itself.

I collected some more info by adding a bit of logging for one of the affected devices.

It looks like the of_node_get() and of_node_put() in the overlay loading phase are the same, even though not completely in the same order. So after overlay insertion we should have the same refcount with and without your patch.

There is a difference on overlay removal however: an of_node_put() call is absent with 6.13-rc1 code (errors emitted), and becomes present by just reverting your patch (the "good" case). Here's the stack trace of this call:

 Call trace:
  show_stack+0x20/0x38 (C)
  dump_stack_lvl+0x74/0x90
  dump_stack+0x18/0x28
  of_node_put+0x50/0x70
  platform_device_release+0x24/0x68
  device_release+0x3c/0xa0
  kobject_put+0xa4/0x118
  device_link_release_fn+0x60/0xd8
  process_one_work+0x158/0x3c0
  worker_thread+0x2d8/0x3e8
  kthread+0x118/0x128
  ret_from_fork+0x10/0x20

Quoted 5 lines

So for some reason device_link_release_fn() is not leading to a of_node_put() call after adding your patch.

Quick code inspection did not show any useful info for me to understand more.

I just sent a patch fixing
this: https://lore.kernel.org/20250212-fix__fw_devlink_relax_cycles_missing_device_put-v1-1-41818c7d7722@bootlin.com

In attempting to optimize fw_devlink runtime, I introduced numerous cycle detection bugs by foregoing cycle detection logic under specific conditions. Each fix has further narrowed the conditions for optimization.

It's time to give up on these optimization attempts and just run the cycle detection logic every time fw_devlink tries to create a device link.

The specific bug report that triggered this fix involved a supplier fwnode that never gets a device created for it. Instead, the supplier fwnode is represented by the device that corresponds to an ancestor fwnode.

In this case, fw_devlink didn't do any cycle detection because the cycle detection logic is only run when a device link is created between the devices that correspond to the actual consumer and supplier fwnodes.

With this change, fw_devlink will run cycle detection logic even when creating SYNC_STATE_ONLY proxy device links from a device that is an ancestor of a consumer fwnode.

Reported-by Tomi Valkeinen <[email protected]>

Closes https://lore.kernel.org/all/[email protected]/ open here

Fixes 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")

Tested-by Tomi Valkeinen <[email protected]>

Signed-off-by Saravana Kannan <[email protected]>

---
  drivers/base/core.c | 55 ++++++++++++++++++++-------------------------
  1 file changed, 24 insertions(+), 31 deletions(-)

Tomi,

Thanks for all the testing and debugging help! And do use post-init-providers even with this patch to improve ordering enforcement. I probably should change the cycle log from info to warn in a separate patch :)