On 05/07/2016 15:11, Alex Bennée wrote:
>
> Paolo Bonzini <pbonz...@redhat.com> writes:
>
>> On 05/07/2016 13:14, Alex Bennée wrote:
>>> /*
>>> * Patch the last TB with a jump to the current TB.
>>> *
>>> * Modification of the TB has to be protected with tb_lock which can
>>> * either be already held or taken here.
>>> */
>>> static inline void maybe_patch_last_tb(CPUState *cpu,
>>> TranslationBlock *tb,
>>> TranslationBlock **last_tb,
>>> int tb_exit,
>>> bool locked)
>>> {
>>> if (cpu->tb_flushed) {
>>> /* Ensure that no TB jump will be modified as the
>>> * translation buffer has been flushed.
>>> */
>>> *last_tb = NULL;
>>> cpu->tb_flushed = false;
>>> }
>>> #ifndef CONFIG_USER_ONLY
>>> /* We don't take care of direct jumps when address mapping changes in
>>> * system emulation. So it's not safe to make a direct jump to a TB
>>> * spanning two pages because the mapping for the second page can
>>> change.
>>> */
>>> if (tb->page_addr[1] != -1) {
>>> *last_tb = NULL;
>>> }
>>> #endif
>>> /* See if we can patch the calling TB. */
>>> if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
>>> if (!locked) {
>>> tb_lock();
>>> }
>>> tb_add_jump(*last_tb, tb_exit, tb);
>>> if (!locked) {
>>> tb_unlock();
>>> }
>>> }
>>> }
>>
>> Why not add tb_lock_recursive() and tb_lock_reset()?
>
> I thought we didn't like having recursive locking? I agree it would make
> things a little neater though.
I didn't like having recursive mutexes (because recursive mutexes
encourage you to be sloppy). Explicitly tagging some tb_lock()s as
recursive is fine, though. The explicit tag tells you to be careful.
Paolo
