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qom: convert the CPU list to RCU

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Iterating over the list without using atomics is undefined behaviour,
since the list can be modified concurrently by other threads (e.g.
every time a new thread is created in user-mode).

Fix it by implementing the CPU list as an RCU QTAILQ. This requires
a little bit of extra work to traverse list in reverse order (see
previous patch), but other than that the conversion is trivial.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <20180819091335.22863-12-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Emilio G. Cota
2018-08-19 05:13:35 -04:00
committed by Paolo Bonzini
parent 04d595b300
commit 068a5ea02f
6 changed files with 11 additions and 12 deletions
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4
cpus-common.c
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@@ -84,7 +84,7 @@ void cpu_list_add(CPUState *cpu)
} else {
assert(!cpu_index_auto_assigned);
}
QTAILQ_INSERT_TAIL(&cpus, cpu, node);
QTAILQ_INSERT_TAIL_RCU(&cpus, cpu, node);
qemu_mutex_unlock(&qemu_cpu_list_lock);
finish_safe_work(cpu);
@@ -101,7 +101,7 @@ void cpu_list_remove(CPUState *cpu)
assert(!(cpu_index_auto_assigned && cpu != QTAILQ_LAST(&cpus, CPUTailQ)));
QTAILQ_REMOVE(&cpus, cpu, node);
QTAILQ_REMOVE_RCU(&cpus, cpu, node);
cpu->cpu_index = UNASSIGNED_CPU_INDEX;
qemu_mutex_unlock(&qemu_cpu_list_lock);
}