bd0f93a630
commit cfd355145c32bb7ccb65fccbe2d67280dc2119e1 upstream.
When cpu_stop_queue_work() releases the lock for the stopper
thread that was queued into its wake queue, preemption is
enabled, which leads to the following deadlock:
CPU0 CPU1
sched_setaffinity(0, ...)
__set_cpus_allowed_ptr()
stop_one_cpu(0, ...) stop_two_cpus(0, 1, ...)
cpu_stop_queue_work(0, ...) cpu_stop_queue_two_works(0, ..., 1, ...)
-grabs lock for migration/0-
-spins with preemption disabled,
waiting for migration/0's lock to be
released-
-adds work items for migration/0
and queues migration/0 to its
wake_q-
-releases lock for migration/0
and preemption is enabled-
-current thread is preempted,
and __set_cpus_allowed_ptr
has changed the thread's
cpu allowed mask to CPU1 only-
-acquires migration/0 and migration/1's
locks-
-adds work for migration/0 but does not
add migration/0 to wake_q, since it is
already in a wake_q-
-adds work for migration/1 and adds
migration/1 to its wake_q-
-releases migration/0 and migration/1's
locks, wakes migration/1, and enables
preemption-
-since migration/1 is requested to run,
migration/1 begins to run and waits on
migration/0, but migration/0 will never
be able to run, since the thread that
can wake it is affine to CPU1-
Disable preemption in cpu_stop_queue_work() before queueing works for
stopper threads, and queueing the stopper thread in the wake queue, to
ensure that the operation of queueing the works and waking the stopper
threads is atomic.
Fixes: 0b26351b910f ("stop_machine, sched: Fix migrate_swap() vs. active_balance() deadlock")
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: matt@codeblueprint.co.uk
Cc: bigeasy@linutronix.de
Cc: gregkh@linuxfoundation.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1533329766-4856-1-git-send-email-isaacm@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-Developed-by: Isaac J. Manjarres <isaacm@codeaurora.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.