Re: [PATCH v1] driver core: Update device link status correctly for SYNC_STATE_ONLY links

On Tue, May 26, 2020 at 12:05 AM Saravana Kannan saravanak@google.com wrote:

When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag"), SYNC_STATE_ONLY links were treated similar to STATELESS links in terms of not blocking consumer probe if the supplier hasn't probed yet.

That caused a SYNC_STATE_ONLY device link's status to not get updated. Since SYNC_STATE_ONLY device link is no longer useful once the consumer probes, commit 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation") addresses the status update issue by deleting the SYNC_STATE_ONLY device link instead of complicating the status update code.

However, there are still some cases where we need to update the status of a SYNC_STATE_ONLY device link. A SYNC_STATE_ONLY device link can later get converted into a normal MANAGED device link when a normal MANAGED device link is created between a supplier and consumer that already have a SYNC_STATE_ONLY device link between them. If a SYNC_STATE_ONLY device link's status isn't maintained correctly till it's converted to a normal MANAGED device link, then the normal MANAGED device link will end up with a wrong link status. This can cause a warning stack trace[1] when the consumer device probes.

This commit fixes the SYNC_STATE_ONLY device link status update issue where it wouldn't transition correctly from DL_STATE_AVAILABLE to DL_STATE_CONSUMER_PROBE.

[1] - https://lore.kernel.org/lkml/20200522204120.3b3c9ed6@apollo/ Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag") Fixes: 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation") Reported-by: Michael Walle michael@walle.cc Signed-off-by: Saravana Kannan saravanak@google.com

---

Greg,

I think this is the issue Michael ran into. I'd like him to test the fix before it's pulled in.

Michael,

If you can test this on the branch you saw the issue in and give a Tested-by if it works, that'd be great.

Thanks, Saravana

drivers/base/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c index 791b7530599f..9511be3f9a32 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -687,11 +687,11 @@ int device_links_check_suppliers(struct device *dev) device_links_write_lock();

    list_for_each_entry(link, &dev->links.suppliers, c_node) {

•           if (!(link->flags & DL_FLAG_MANAGED) ||
  

•               link->flags & DL_FLAG_SYNC_STATE_ONLY)
  

•           if (!(link->flags & DL_FLAG_MANAGED))
                    continue;
  
  

•           if (link->status != DL_STATE_AVAILABLE) {
  

•           if (link->status != DL_STATE_AVAILABLE &&
  

•               !(link->flags & DL_FLAG_SYNC_STATE_ONLY)) {
                    device_links_missing_supplier(dev);
                    ret = -EPROBE_DEFER;
                    break;
  

-- 2.27.0.rc0.183.gde8f92d652-goog

Adding stable@ that I forgot to add earlier.

-Saravana