user/sven/linux.git/kernel/stop_machine.c, branch v4.4.10

kernel: remove stop_machine() Kconfig dependency

2015-12-12T18:15:34Z

Currently the full stop_machine() routine is only enabled on SMP if module unloading is enabled, or if the CPUs are hotpluggable. This leads to configurations where stop_machine() is broken as it will then only run the callback on the local CPU with irqs disabled, and not stop the other CPUs or run the callback on them. For example, this breaks MTRR setup on x86 in certain configs since ea8596bb2d8d379 ("kprobes/x86: Remove unused text_poke_smp() and text_poke_smp_batch() functions") as the MTRR is only established on the boot CPU. This patch removes the Kconfig option for STOP_MACHINE and uses the SMP and HOTPLUG_CPU config options to compile the correct stop_machine() for the architecture, removing the false dependency on MODULE_UNLOAD in the process. Link: https://lkml.org/lkml/2014/10/8/124 References: https://bugs.freedesktop.org/show_bug.cgi?id=84794 Signed-off-by: Chris Wilson Acked-by: Ingo Molnar Cc: "Paul E. McKenney" Cc: Pranith Kumar Cc: Michal Hocko Cc: Vladimir Davydov Cc: Johannes Weiner Cc: H. Peter Anvin Cc: Tejun Heo Cc: Iulia Manda Cc: Andy Lutomirski Cc: Rusty Russell Cc: Peter Zijlstra Cc: Chuck Ebbert Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sched: Move cpu_active() tests from stop_two_cpus() into migrate_swap_stop()

2015-10-20T08:25:56Z

The cpu_active() tests are not fundamentally part of stop_two_cpus(), move then into the scheduler where they belong. Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar

stop_machine: Kill cpu_stop_threads->setup() and cpu_stop_unpark()

2015-10-20T08:23:56Z

Now that we always use stop_machine_unpark() to wake the stopper threas up, we can kill ->setup() and fold cpu_stop_unpark() into stop_machine_unpark(). And we do not need stopper->lock to set stopper->enabled = true. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151009160051.GA10169@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark()

2015-10-20T08:23:55Z

1. Change smpboot_unpark_thread() to check ->selfparking, just like smpboot_park_thread() does. 2. Introduce stop_machine_unpark() which sets ->enabled and calls kthread_unpark(). 3. Change smpboot_thread_call() and cpu_stop_init() to call stop_machine_unpark() by hand. This way: - IMO the ->selfparking logic becomes more consistent. - We can kill the smp_hotplug_thread->pre_unpark() method. - We can easily unpark the stopper thread earlier. Say, we can move stop_machine_unpark() from smpboot_thread_call() to sched_cpu_active() as Peter suggests. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151009160049.GA10166@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Change cpu_stop_queue_two_works() to rely on stopper->enabled

2015-10-20T08:23:55Z

Change cpu_stop_queue_two_works() to ensure that both CPU's have stopper->enabled == T or fail otherwise. This way stop_two_cpus() no longer needs to check cpu_active() to avoid the deadlock. This patch doesn't remove these checks, we will do this later. Note: we need to take both stopper->lock's at the same time, but this will also help to remove lglock from stop_machine.c, so I hope this is fine. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151008170141.GA25537@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Introduce __cpu_stop_queue_work() and cpu_stop_queue_two_works()

2015-10-20T08:23:54Z

Preparation to simplify the review of the next change. Add two simple helpers, __cpu_stop_queue_work() and cpu_stop_queue_two_works() which simply take a bit of code from their callers. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151008145134.GA18146@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Ensure that a queued callback will be called before cpu_stop_park()

2015-10-20T08:23:53Z

cpu_stop_queue_work() checks stopper->enabled before it queues the work, but ->enabled == T can only guarantee cpu_stop_signal_done() if we race with cpu_down(). This is not enough for stop_two_cpus() or stop_machine(), they will deadlock if multi_cpu_stop() won't be called by one of the target CPU's. stop_machine/stop_cpus are fine, they rely on stop_cpus_mutex. But stop_two_cpus() has to check cpu_active() to avoid the same race with hotplug, and this check is very unobvious and probably not even correct if we race with cpu_up(). Change cpu_down() pass to clear ->enabled before cpu_stopper_thread() flushes the pending ->works and returns with KTHREAD_SHOULD_PARK set. Note also that smpboot_thread_call() calls cpu_stop_unpark() which sets enabled == T at CPU_ONLINE stage, so this CPU can't go away until cpu_stopper_thread() is called at least once. This all means that if cpu_stop_queue_work() succeeds, we know that work->fn() will be called. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151008145131.GA18139@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Remove cpu_stop_work's from list in cpu_stop_park()

2015-08-03T10:21:28Z

cpu_stop_park() does cpu_stop_signal_done() but leaves the work on stopper->works. The owner of this work can free/reuse this memory right after that and corrupt the list, so if this CPU becomes online again cpu_stopper_thread() will crash. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Tejun Heo Cc: Thomas Gleixner Cc: dave@stgolabs.net Cc: der.herr@hofr.at Cc: paulmck@linux.vnet.ibm.com Cc: riel@redhat.com Cc: viro@ZenIV.linux.org.uk Link: http://lkml.kernel.org/r/20150630012958.GA23944@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Use 'cpu_stop_fn_t' where possible

2015-08-03T10:21:27Z

Cosmetic, but 'cpu_stop_fn_t' actually makes the code more readable and it doesn't break cscope. And most of the declarations already use it. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Tejun Heo Cc: Thomas Gleixner Cc: dave@stgolabs.net Cc: der.herr@hofr.at Cc: paulmck@linux.vnet.ibm.com Cc: riel@redhat.com Cc: viro@ZenIV.linux.org.uk Link: http://lkml.kernel.org/r/20150630012955.GA23937@redhat.com Signed-off-by: Ingo Molnar

stop_machine: Unexport __stop_machine()

2015-08-03T10:21:26Z

The only caller outside of stop_machine.c is _cpu_down(), it can use stop_machine(). get_online_cpus() is fine under cpu_hotplug_begin(). Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Tejun Heo Cc: Thomas Gleixner Cc: dave@stgolabs.net Cc: der.herr@hofr.at Cc: paulmck@linux.vnet.ibm.com Cc: riel@redhat.com Cc: viro@ZenIV.linux.org.uk Link: http://lkml.kernel.org/r/20150630012951.GA23934@redhat.com Signed-off-by: Ingo Molnar