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move_to_close_lru() waits for sc_count to become zero while holding rp_mutex. This can deadlock if another thread holds a reference and is waiting for rp_mutex. By the time we get to move_to_close_lru() the openowner is unhashed and cannot be found any more. So code waiting for the mutex can safely retry the lookup if move_to_close_lru() has started. So change rp_mutex to an atomic_t with three states: RP_UNLOCK - state is still hashed, not locked for reply RP_LOCKED - state is still hashed, is locked for reply RP_UNHASHED - state is not hashed, no code can get a lock. Use wait_var_event() to wait for either a lock, or for the owner to be unhashed. In the latter case, retry the lookup. Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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 reStructuredText 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.