Commit 512d3c80 authored by Alex Bennée's avatar Alex Bennée
Browse files

cpus: introduce cpu_update_icount helper 



By holding off updates to timer_state.qemu_icount we can run into
trouble when the non-vCPU thread needs to know the time. This helper
ensures we atomically update timers_state.qemu_icount based on what
has been currently executed.

Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
parent e4cd9657

cpus.c

+21 −2
Original line number Diff line number Diff line
@@ -232,12 +232,31 @@ static int64_t cpu_get_icount_executed(CPUState *cpu) 
    return cpu->icount_budget - (cpu->icount_decr.u16.low + cpu->icount_extra);

}



/*

 * Update the global shared timer_state.qemu_icount to take into

 * account executed instructions. This is done by the TCG vCPU

 * thread so the main-loop can see time has moved forward.

 */

void cpu_update_icount(CPUState *cpu)

{

    int64_t executed = cpu_get_icount_executed(cpu);

    cpu->icount_budget -= executed;



#ifdef CONFIG_ATOMIC64

    atomic_set__nocheck(&timers_state.qemu_icount,

                        atomic_read__nocheck(&timers_state.qemu_icount) +

                        executed);

#else /* FIXME: we need 64bit atomics to do this safely */

    timers_state.qemu_icount += executed;

#endif

}



int64_t cpu_get_icount_raw(void)

{

    int64_t icount;

    CPUState *cpu = current_cpu;



    icount = timers_state.qemu_icount;

    icount = atomic_read(&timers_state.qemu_icount);

    if (cpu && cpu->running) {

        if (!cpu->can_do_io) {

            fprintf(stderr, "Bad icount read\n");
@@ -1220,7 +1239,7 @@ static void process_icount_data(CPUState *cpu) 
{

    if (use_icount) {

        /* Account for executed instructions */

        timers_state.qemu_icount += cpu_get_icount_executed(cpu);

        cpu_update_icount(cpu);



        /* Reset the counters */

        cpu->icount_decr.u16.low = 0;

include/qemu/timer.h

+1 −0
Original line number Diff line number Diff line
@@ -869,6 +869,7 @@ int64_t cpu_get_icount_raw(void); 
int64_t cpu_get_icount(void);

int64_t cpu_get_clock(void);

int64_t cpu_icount_to_ns(int64_t icount);

void    cpu_update_icount(CPUState *cpu);



/*******************************************/

/* host CPU ticks (if available) */