Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 14 Nov 2019 23:45:24 +0100 | Subject | Re: [PATCH v3] driver core: Allow device link operations inside sync_state() |
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On Thu, Nov 14, 2019 at 11:23 PM Saravana Kannan <saravanak@google.com> wrote: > > Some sync_state() implementations might need to call APIs that in turn > make calls to device link APIs. So, do the sync_state() callbacks > without holding the device link lock. > > Signed-off-by: Saravana Kannan <saravanak@google.com> > --- > drivers/base/core.c | 80 ++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 72 insertions(+), 8 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index e6d3e6d485da..9a88bcfd5d33 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -695,7 +695,26 @@ int device_links_check_suppliers(struct device *dev) > return ret; > } > > -static void __device_links_supplier_sync_state(struct device *dev) > +/** > + * __device_links_queue_sync_state - Queue a device for sync_state() callback > + * @dev: Device to call sync_state() on > + * @list: List head to queue the @dev on > + * > + * Queues a device for a sync_state() callback when the device links write lock > + * isn't held. This allows the sync_state() execution flow to use device links > + * APIs. The caller must ensure this function is called with > + * device_links_write_lock() held. > + * > + * This function does a get_device() to make sure the device is not freed while > + * on this list. > + * > + * So the caller must also ensure that device_links_flush_sync_list() is called > + * as soon as the caller releases device_links_write_lock(). This is necessary > + * to make sure the sync_state() is called in a timely fashion and the > + * put_device() is called on this device. > + */ > +static void __device_links_queue_sync_state(struct device *dev, > + struct list_head *list) > { > struct device_link *link; > > @@ -709,12 +728,46 @@ static void __device_links_supplier_sync_state(struct device *dev) > return; > } > > - if (dev->bus->sync_state) > - dev->bus->sync_state(dev); > - else if (dev->driver && dev->driver->sync_state) > - dev->driver->sync_state(dev); > - > + /* > + * Set the flag here to avoid adding the same device to a list more > + * than once. This can happen if new consumers get added to the device > + * and probed before the list is flushed. > + */ > dev->state_synced = true; > + > + if (list_empty(&dev->links.defer_sync)) { > + get_device(dev); > + list_add_tail(&dev->links.defer_sync, list); > + } else { > + WARN_ON(1); > + }
Now you can do:
if (WARN_ON(!list_empty(&dev->links.defer_sync))) return;
get_device(dev); list_add_tail(&dev->links.defer_sync, list);
The rest of the patch LGTM.
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