Messages in this thread | | | Date | Mon, 25 May 2020 13:31:27 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v3] driver core: Fix SYNC_STATE_ONLY device link implementation |
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Am 2020-05-23 00:47, schrieb Michael Walle: > Am 2020-05-23 00:21, schrieb Saravana Kannan: >> On Fri, May 22, 2020 at 11:41 AM Michael Walle <michael@walle.cc> >> wrote: >>> >>> Am Mon, 18 May 2020 23:30:00 -0700 >>> schrieb Saravana Kannan <saravanak@google.com>: >>> >>> > When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("driver >>> > core: Add device link support for SYNC_STATE_ONLY flag"), >>> > device_link_add() incorrectly skipped adding the new SYNC_STATE_ONLY >>> > device link to the supplier's and consumer's "device link" list. >>> > >>> > This causes multiple issues: >>> > - The device link is lost forever from driver core if the caller >>> > didn't keep track of it (caller typically isn't expected to). This >>> > is a memory leak. >>> > - The device link is also never visible to any other code path after >>> > device_link_add() returns. >>> > >>> > If we fix the "device link" list handling, that exposes a bunch of >>> > issues. >>> > >>> > 1. The device link "status" state management code rightfully doesn't >>> > handle the case where a DL_FLAG_MANAGED device link exists between a >>> > supplier and consumer, but the consumer manages to probe successfully >>> > before the supplier. The addition of DL_FLAG_SYNC_STATE_ONLY links >>> > break this assumption. This causes device_links_driver_bound() to >>> > throw a warning when this happens. >>> > >>> > Since DL_FLAG_SYNC_STATE_ONLY device links are mainly used for >>> > creating proxy device links for child device dependencies and aren't >>> > useful once the consumer device probes successfully, this patch just >>> > deletes DL_FLAG_SYNC_STATE_ONLY device links once its consumer device >>> > probes. This way, we avoid the warning, free up some memory and avoid >>> > complicating the device links "status" state management code. >>> > >>> > 2. Creating a DL_FLAG_STATELESS device link between two devices that >>> > already have a DL_FLAG_SYNC_STATE_ONLY device link will result in the >>> > DL_FLAG_STATELESS flag not getting set correctly. This patch also >>> > fixes this. >>> > >>> > Lastly, this patch also fixes minor whitespace issues. >>> >>> My board triggers the >>> WARN_ON(link->status != DL_STATE_CONSUMER_PROBE); >>> >>> Full bootlog: > [..] > >> Thanks for the log and report. I haven't spent too much time thinking >> about this, but can you give this a shot? >> https://lore.kernel.org/lkml/20200520043626.181820-1-saravanak@google.com/ > > I've already tried that, as this is already in linux-next. Doesn't fix > it, > though.
btw. this only happens on linux-next (tested with next-20200522), not on 5.7-rc7 (which has the same two patches of yours)
-michael
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