On 05/04/2017 15:25, Alex Bennée wrote:
> This ensures each time the vCPU thread reads the icount we update the
> master timer_state.qemu_icount field. This way as long as updates are
> in BQL protected sections (which they should be) the main-loop can
> never come to update the log and find time has gone backwards.
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
> ---
> cpus.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index ff75af449a..63de033cc8 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -246,19 +246,17 @@ void cpu_update_icount(CPUState *cpu)
>
> int64_t cpu_get_icount_raw(void)
> {
> - int64_t icount;
> CPUState *cpu = current_cpu;
>
> - icount = atomic_read(&timers_state.qemu_icount);
> if (cpu && cpu->running) {
> if (!cpu->can_do_io) {
> fprintf(stderr, "Bad icount read\n");
> exit(1);
> }
> /* Take into account what has run */
> - icount += cpu_get_icount_executed(cpu);
> + cpu_update_icount(cpu);
> }
> - return icount;
> + return atomic_read(&timers_state.qemu_icount);
> }
>
> /* Return the virtual CPU time, based on the instruction counter. */
>
Maybe the update should be done in gen_io_start instead. There
shouldn't be any interference between vCPU and I/O threads except
between gen_io_start and gen_io_end.
Paolo
