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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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2
linux-user/main.c
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@ -126,7 +126,7 @@ void fork_end(int child)
Discard information about the parent threads. */
CPU_FOREACH_SAFE(cpu, next_cpu) {
if (cpu != thread_cpu) {
QTAILQ_REMOVE(&cpus, cpu, node);
QTAILQ_REMOVE_RCU(&cpus, cpu, node);
}
}
qemu_init_cpu_list();