75 lines
3.0 KiB
Diff
75 lines
3.0 KiB
Diff
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# Commit 41a0cc9e26160a89245c9ba3233e3f70bf9cd4b4
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# Date 2013-10-29 09:57:14 +0100
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# Author Jan Beulich <jbeulich@suse.com>
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# Committer Jan Beulich <jbeulich@suse.com>
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fix locking in cpu_disable_scheduler()
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So commit eedd6039 ("scheduler: adjust internal locking interface")
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uncovered - by now using proper spin lock constructs - a bug after all:
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When bringing down a CPU, cpu_disable_scheduler() gets called with
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interrupts disabled, and hence the use of vcpu_schedule_lock_irq() was
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never really correct (i.e. the caller ended up with interrupts enabled
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despite having disabled them explicitly).
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Fixing this however surfaced another problem: The call path
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vcpu_migrate() -> evtchn_move_pirqs() wants to acquire the event lock,
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which however is a non-IRQ-safe once, and hence check_lock() doesn't
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like this lock to be acquired when interrupts are already off. As we're
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in stop-machine context here, getting things wrong wrt interrupt state
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management during lock acquire/release is out of question though, so
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the simple solution to this appears to be to just suppress spin lock
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debugging for the period of time while the stop machine callback gets
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run.
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Signed-off-by: Jan Beulich <jbeulich@suse.com>
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Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Acked-by: Keir Fraser <keir@xen.org>
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--- a/xen/common/schedule.c
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+++ b/xen/common/schedule.c
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@@ -600,7 +600,8 @@ int cpu_disable_scheduler(unsigned int c
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{
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for_each_vcpu ( d, v )
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{
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- spinlock_t *lock = vcpu_schedule_lock_irq(v);
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+ unsigned long flags;
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+ spinlock_t *lock = vcpu_schedule_lock_irqsave(v, &flags);
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cpumask_and(&online_affinity, v->cpu_affinity, c->cpu_valid);
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if ( cpumask_empty(&online_affinity) &&
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@@ -621,14 +622,12 @@ int cpu_disable_scheduler(unsigned int c
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if ( v->processor == cpu )
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{
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set_bit(_VPF_migrating, &v->pause_flags);
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- vcpu_schedule_unlock_irq(lock, v);
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+ vcpu_schedule_unlock_irqrestore(lock, flags, v);
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vcpu_sleep_nosync(v);
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vcpu_migrate(v);
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}
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else
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- {
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- vcpu_schedule_unlock_irq(lock, v);
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- }
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+ vcpu_schedule_unlock_irqrestore(lock, flags, v);
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/*
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* A vcpu active in the hypervisor will not be migratable.
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--- a/xen/common/stop_machine.c
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+++ b/xen/common/stop_machine.c
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@@ -110,6 +110,7 @@ int stop_machine_run(int (*fn)(void *),
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local_irq_disable();
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stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
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stopmachine_wait_state();
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+ spin_debug_disable();
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stopmachine_set_state(STOPMACHINE_INVOKE);
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if ( (cpu == smp_processor_id()) || (cpu == NR_CPUS) )
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@@ -117,6 +118,7 @@ int stop_machine_run(int (*fn)(void *),
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stopmachine_wait_state();
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ret = stopmachine_data.fn_result;
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+ spin_debug_enable();
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stopmachine_set_state(STOPMACHINE_EXIT);
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stopmachine_wait_state();
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local_irq_enable();
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