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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: Alex Bennée <alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2017-04-05 12:32:37 +01:00
parent e4cd96571f
commit 512d3c8071
2 changed files with 22 additions and 2 deletions
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23
cpus.c
View File

@ -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;

1
include/qemu/timer.h
View File

@ -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) */