On 19/01/2018 13:05, Pavel Dovgalyuk wrote:
>> From: Paolo Bonzini [mailto:[email protected]]
>> On 19/01/2018 09:44, Pavel Dovgalyuk wrote:
>>> while (all_cpu_threads_idle()) {
>>> + qemu_mutex_lock_iothread();
>>> stop_tcg_kick_timer();
>>> qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
>>> + qemu_mutex_unlock_iothread();
>>> }
>>
>> cpu_has_work cannot be called outside BQL yet. You first need to access
>> cpu->interrupt_request with atomics.
>>
>> In general, testing the condition outside the mutex is a very dangerous
>> pattern (and I'm usually the one who enjoys dangerous patterns).
>
> It means, that I'll have to fix all the has_work function to avoid races,
> because x86_cpu_has_work may have them?
Why only x86_cpu_has_work?
Even reading cs->interrupt_request outside the mutex is unsafe.
Paolo
> static bool x86_cpu_has_work(CPUState *cs)
> {
> X86CPU *cpu = X86_CPU(cs);
> CPUX86State *env = &cpu->env;
>
> return ((cs->interrupt_request & (CPU_INTERRUPT_HARD |
> CPU_INTERRUPT_POLL)) &&
> (env->eflags & IF_MASK)) ||
> (cs->interrupt_request & (CPU_INTERRUPT_NMI |
> CPU_INTERRUPT_INIT |
> CPU_INTERRUPT_SIPI |
> CPU_INTERRUPT_MCE)) ||
> ((cs->interrupt_request & CPU_INTERRUPT_SMI) &&
> !(env->hflags & HF_SMM_MASK));
> }
>
> Pavel Dovgalyuk
>
