On 01/10/19 19:40, Alex Bennée wrote:
>
> Paolo Bonzini <pbonz...@redhat.com> writes:
>
>> On 01/10/19 18:04, Alex Bennée wrote:
>>> qemu_cpu_kick is used for a number of reasons including to indicate
>>> there is work to be done. However when thread=single the old
>>> qemu_cpu_kick_rr_cpu only advanced the vCPU to the next executing one
>>> which can lead to a hang in the case that:
>>>
>>> a) the kick is from outside the vCPUs (e.g. iothread)
>>> b) the timers are paused (i.e. iothread calling run_on_cpu)
>>>
>>> To avoid this lets split qemu_cpu_kick_rr into two functions. One for
>>> the timer which continues to advance to the next timeslice and another
>>> for all other kicks.
>>>
>>> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
>>> Cc: Doug Gale <doug...@gmail.com>
>>> Cc: Paolo Bonzini <pbonz...@redhat.com>
>>> Cc: Peter Maydell <peter.mayd...@linaro.org>
>>> ---
>>> cpus.c | 24 ++++++++++++++++++------
>>> 1 file changed, 18 insertions(+), 6 deletions(-)
>>
>> Looks good to me. Single-threaded TCG is not going to have high vCPU
>> counts anyway.
>
> Are you going to take this via your queue?
I wasn't, since we have had a proper TCG maintainer for a while. :)
Paolo
>
>>
>> Paolo
>>
>>> diff --git a/cpus.c b/cpus.c
>>> index d2c61ff155..bee7209134 100644
>>> --- a/cpus.c
>>> +++ b/cpus.c
>>> @@ -949,8 +949,8 @@ static inline int64_t qemu_tcg_next_kick(void)
>>> return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
>>> }
>>>
>>> -/* Kick the currently round-robin scheduled vCPU */
>>> -static void qemu_cpu_kick_rr_cpu(void)
>>> +/* Kick the currently round-robin scheduled vCPU to next */
>>> +static void qemu_cpu_kick_rr_next_cpu(void)
>>> {
>>> CPUState *cpu;
>>> do {
>>> @@ -961,6 +961,16 @@ static void qemu_cpu_kick_rr_cpu(void)
>>> } while (cpu != atomic_mb_read(&tcg_current_rr_cpu));
>>> }
>>>
>>> +/* Kick all RR vCPUs */
>>> +static void qemu_cpu_kick_rr_cpus(void)
>>> +{
>>> + CPUState *cpu;
>>> +
>>> + CPU_FOREACH(cpu) {
>>> + cpu_exit(cpu);
>>> + };
>>> +}
>>> +
>>> static void do_nothing(CPUState *cpu, run_on_cpu_data unused)
>>> {
>>> }
>>> @@ -993,7 +1003,7 @@ void qemu_timer_notify_cb(void *opaque, QEMUClockType
>>> type)
>>> static void kick_tcg_thread(void *opaque)
>>> {
>>> timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
>>> - qemu_cpu_kick_rr_cpu();
>>> + qemu_cpu_kick_rr_next_cpu();
>>> }
>>>
>>> static void start_tcg_kick_timer(void)
>>> @@ -1828,9 +1838,11 @@ void qemu_cpu_kick(CPUState *cpu)
>>> {
>>> qemu_cond_broadcast(cpu->halt_cond);
>>> if (tcg_enabled()) {
>>> - cpu_exit(cpu);
>>> - /* NOP unless doing single-thread RR */
>>> - qemu_cpu_kick_rr_cpu();
>>> + if (qemu_tcg_mttcg_enabled()) {
>>> + cpu_exit(cpu);
>>> + } else {
>>> + qemu_cpu_kick_rr_cpus();
>>> + }
>>> } else {
>>> if (hax_enabled()) {
>>> /*
>>>
>
>
> --
> Alex Bennée
>
