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[ Upstream commit13b7955a02] Standard kernel mutexes cannot be used in any way from interrupt or softirq context, so the user_mutex which manages access to a call cannot be a mutex since on a new call the mutex must start off locked and be unlocked within the softirq handler to prevent userspace interfering with a call we're setting up. Commita0855d24fc("locking/mutex: Complain upon mutex API misuse in IRQ contexts") causes big warnings to be splashed in dmesg for each a new call that comes in from the server. Whilst it *seems* like it should be okay, since the accept path uses trylock, there are issues with PI boosting and marking the wrong task as the owner. Fix this by not taking the mutex in the softirq path at all. It's not obvious that there should be any need for it as the state is set before the first notification is generated for the new call. There's also no particular reason why the link-assessing ping should be triggered inside the mutex. It's not actually transmitted there anyway, but rather it has to be deferred to a workqueue. Further, I don't think that there's any particular reason that the socket notification needs to be done from within rx->incoming_lock, so the amount of time that lock is held can be shortened too and the ping prepared before the new call notification is sent. Fixes:540b1c48c3("rxrpc: Fix deadlock between call creation and sendmsg/recvmsg") Signed-off-by: David Howells <dhowells@redhat.com> cc: Peter Zijlstra (Intel) <peterz@infradead.org> cc: Ingo Molnar <mingo@redhat.com> cc: Will Deacon <will@kernel.org> cc: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.