Commit e8f22f76 authored by Alex Bennée's avatar Alex Bennée Committed by Richard Henderson
Browse files

cpus: kick all vCPUs when running thread=single 



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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
parent b7ce3cff

cpus.c

+18 −6
Original line number Diff line number Diff line
@@ -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()) {

        if (qemu_tcg_mttcg_enabled()) {

            cpu_exit(cpu);

        /* NOP unless doing single-thread RR */

        qemu_cpu_kick_rr_cpu();

        } else {

            qemu_cpu_kick_rr_cpus();

        }

    } else {

        if (hax_enabled()) {

            /*