On 08/11/2016 08:24 AM, Alex Bennée wrote:
Currently we rely on the side effect of the main loop grabbing the iothread_mutex to give any long running basic block chains a kick to ensure the next vCPU is scheduled. As this code is being re-factored and rationalised we now do it explicitly here.Signed-off-by: Alex Bennée <alex.ben...@linaro.org> --- v2 - re-base fixes - get_ticks_per_sec() -> NANOSECONDS_PER_SEC v3 - add define for TCG_KICK_FREQ - fix checkpatch warning v4 - wrap next calc in inline qemu_tcg_next_kick() instead of macro --- cpus.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/cpus.c b/cpus.c index b5b45b8..8c49d6c 100644 --- a/cpus.c +++ b/cpus.c @@ -1185,9 +1185,34 @@ static void deal_with_unplugged_cpus(void) } } +/* Single-threaded TCG + * + * In the single-threaded case each vCPU is simulated in turn. If + * there is more than a single vCPU we create a simple timer to kick + * the vCPU and ensure we don't get stuck in a tight loop in one vCPU. + * This is done explicitly rather than relying on side-effects + * elsewhere. + */ +static void qemu_cpu_kick_no_halt(void); + +#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10) + +static inline int64_t qemu_tcg_next_kick(void) +{ + return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD; +} + +static void kick_tcg_thread(void *opaque) +{ + QEMUTimer *self = *(QEMUTimer **) opaque; + timer_mod(self, qemu_tcg_next_kick()); + qemu_cpu_kick_no_halt(); +} + static void *qemu_tcg_cpu_thread_fn(void *arg) { CPUState *cpu = arg; + QEMUTimer *kick_timer; rcu_register_thread(); @@ -1211,6 +1236,13 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) } } + /* Set to kick if we have to do more than one vCPU */ + if (CPU_NEXT(first_cpu)) { + kick_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, kick_tcg_thread, + &kick_timer);
I'm not especially keen on this pointer to local variable thing. Perhaps better as kick_timer = timer_new_ns(..., NULL); kick_timer->opaque = kick_timer; and avoid the indirection in kick_tcg_thread. Also, we should shut down the timer when the cpu is removed, surely? r~
