On Wed, 06/24 18:25, Paolo Bonzini wrote:
> The next patch will require the BQL to be always taken with
> qemu_mutex_lock_iothread(), while right now this isn't the case.
>
> Outside TCG mode this is not a problem. In TCG mode, we need to be
> careful and avoid the "prod out of compiled code" step if already
> in a VCPU thread. This is easily done with a check on current_cpu,
> i.e. qemu_in_vcpu_thread().
>
> Hopefully, multithreaded TCG will get rid of the whole logic to kick
> VCPUs whenever an I/O event occurs!
>
> Cc: Frederic Konrad <fred.kon...@greensocs.com>
> Message-Id: <1434646046-27150-2-git-send-email-pbonz...@redhat.com>
Why is this "Message-Id:" included in the commit message if it's not final?
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> cpus.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index b85fb5f..02cca5d 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -953,7 +953,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
> CPUState *cpu = arg;
> int r;
>
> - qemu_mutex_lock(&qemu_global_mutex);
> + qemu_mutex_lock_iothread();
> qemu_thread_get_self(cpu->thread);
> cpu->thread_id = qemu_get_thread_id();
> cpu->can_do_io = 1;
> @@ -1033,10 +1033,10 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
> {
> CPUState *cpu = arg;
>
> + qemu_mutex_lock_iothread();
> qemu_tcg_init_cpu_signals();
> qemu_thread_get_self(cpu->thread);
>
> - qemu_mutex_lock(&qemu_global_mutex);
> CPU_FOREACH(cpu) {
> cpu->thread_id = qemu_get_thread_id();
> cpu->created = true;
> @@ -1148,7 +1148,11 @@ bool qemu_in_vcpu_thread(void)
> void qemu_mutex_lock_iothread(void)
> {
> atomic_inc(&iothread_requesting_mutex);
> - if (!tcg_enabled() || !first_cpu || !first_cpu->thread) {
> + /* In the simple case there is no need to bump the VCPU thread out of
> + * TCG code execution.
> + */
> + if (!tcg_enabled() || qemu_in_vcpu_thread() ||
> + !first_cpu || !first_cpu->thread) {
This looks like a separate change from the above
"qemu_mutex_lock(&qemu_global_mutex)" conversion. Why do they belong to the
same patch?
Fam
> qemu_mutex_lock(&qemu_global_mutex);
> atomic_dec(&iothread_requesting_mutex);
> } else {
> --
> 1.8.3.1
>
>
