linux-user: properly "unrealize" vCPU object
We shouldn't be messing around with the CPU list in linux-user save for the very special case of do_fork(). When threads end we need to properly follow QOM object lifetime handling and allow the eventual cpu_common_unrealizefn to both remove the CPU and ensure any clean-up actions are taken place, for example calling plugin exit hooks. There is still a race condition to avoid so use the linux-user specific clone_lock instead of the cpu_list_lock to avoid it. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Cc: Nikolay Igotti <igotti@gmail.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Daniel P. Berrange <berrange@redhat.com> Cc: Eduardo Habkost <ehabkost@redhat.com> Cc: Markus Armbruster <armbru@redhat.com> Message-Id: <20200520140541.30256-14-alex.bennee@linaro.org>
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@ -7635,30 +7635,33 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
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return -TARGET_ERESTARTSYS;
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}
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cpu_list_lock();
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pthread_mutex_lock(&clone_lock);
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if (CPU_NEXT(first_cpu)) {
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TaskState *ts;
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TaskState *ts = cpu->opaque;
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/* Remove the CPU from the list. */
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QTAILQ_REMOVE_RCU(&cpus, cpu, node);
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object_property_set_bool(OBJECT(cpu), false, "realized", NULL);
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object_unref(OBJECT(cpu));
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/*
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* At this point the CPU should be unrealized and removed
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* from cpu lists. We can clean-up the rest of the thread
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* data without the lock held.
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*/
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cpu_list_unlock();
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pthread_mutex_unlock(&clone_lock);
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ts = cpu->opaque;
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if (ts->child_tidptr) {
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put_user_u32(0, ts->child_tidptr);
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do_sys_futex(g2h(ts->child_tidptr), FUTEX_WAKE, INT_MAX,
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NULL, NULL, 0);
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}
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thread_cpu = NULL;
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object_unref(OBJECT(cpu));
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g_free(ts);
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rcu_unregister_thread();
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pthread_exit(NULL);
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}
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cpu_list_unlock();
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pthread_mutex_unlock(&clone_lock);
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preexit_cleanup(cpu_env, arg1);
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_exit(arg1);
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return 0; /* avoid warning */
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