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commitc749d8c018upstream. Currently css_wait_for_slow_path() gets called inside the chp->lock. The path-verification-loop of slowpath inside this lock could lead to deadlock as reported by the lockdep validator. The ccw_device_get_chp_desc() during the instance of a device-set-online would try to acquire the same 'chp->lock' to read the chp->desc. The instance of this function can get called from multiple scenario, like probing or setting-device online manually. This could, in some corner-cases lead to the deadlock. lockdep validator reported this as, CPU0 CPU1 ---- ---- lock(&chp->lock); lock(kn->active#43); lock(&chp->lock); lock((wq_completion)cio); The chp->lock was introduced to serialize the access of struct channel_path. This lock is not needed for the css_wait_for_slow_path() function, so invoke the slow-path function outside this lock. Fixes:b730f3a933("[S390] cio: add lock to struct channel_path") Cc: <stable@vger.kernel.org> Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com> Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.