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cpus: kick all vCPUs when running thread=single

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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.

Message-Id: <20191001160426.26644-1-alex.bennee@linaro.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Alex Bennée 2019-10-01 17:04:26 +01:00 committed by Richard Henderson
parent b7ce3cff21
commit e8f22f7684
1 changed files with 18 additions and 6 deletions
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24
cpus.c
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@ -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()) {
/*