Re: [Qemu-devel] [PATCH v2 3/3] Add a 'name' parameter to qemu_thread_create

[Laszlo Ersek <lersek@redhat.com>]

comments below

On 01/30/14 11:20, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> If enabled, set the thread name at creation (on GNU systems with
>   pthread_set_np)
> Fix up all the callers with a thread name
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  cpus.c                          | 25 ++++++++++++++++++++-----
>  hw/block/dataplane/virtio-blk.c |  2 +-
>  hw/usb/ccid-card-emulated.c     |  8 ++++----
>  include/qemu/thread.h           |  2 +-
>  libcacard/vscclient.c           |  2 +-
>  migration.c                     |  2 +-
>  thread-pool.c                   |  2 +-
>  ui/vnc-jobs.c                   |  3 ++-
>  util/compatfd.c                 |  3 ++-
>  util/qemu-thread-posix.c        |  9 +++++++--
>  util/qemu-thread-win32.c        |  2 +-
>  11 files changed, 41 insertions(+), 19 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index ca4c59f..e5bb271 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -1117,16 +1117,23 @@ void resume_all_vcpus(void)
>      }
>  }
>  
> +/* For temporary buffers for forming a name */
> +#define TMP_THREAD_NAME_LEN 16

This should be called _SIZE in my opinion, because it seems to include
the trailing NUL character.

Alternatively, as much as I hate glib's presence in qemu, you could
replace each (fixed size buffer, snprintf()) pair with a (pointer,
g_strdup_printf(), g_free()) triplet.

> +
>  static void qemu_tcg_init_vcpu(CPUState *cpu)
>  {
> +    char thread_name[TMP_THREAD_NAME_LEN];
> +
>      /* share a single thread for all cpus with TCG */
>      if (!tcg_cpu_thread) {
>          cpu->thread = g_malloc0(sizeof(QemuThread));
>          cpu->halt_cond = g_malloc0(sizeof(QemuCond));
>          qemu_cond_init(cpu->halt_cond);
>          tcg_halt_cond = cpu->halt_cond;
> -        qemu_thread_create(cpu->thread, qemu_tcg_cpu_thread_fn, cpu,
> -                           QEMU_THREAD_JOINABLE);
> +        snprintf(thread_name, TMP_THREAD_NAME_LEN, "CPU %d/TCG",
> +                 cpu->cpu_index);
> +        qemu_thread_create(cpu->thread, thread_name, qemu_tcg_cpu_thread_fn,
> +                           cpu, QEMU_THREAD_JOINABLE);
>  #ifdef _WIN32
>          cpu->hThread = qemu_thread_get_handle(cpu->thread);
>  #endif
> @@ -1142,11 +1149,15 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
>  
>  static void qemu_kvm_start_vcpu(CPUState *cpu)
>  {
> +    char thread_name[TMP_THREAD_NAME_LEN];
> +
>      cpu->thread = g_malloc0(sizeof(QemuThread));
>      cpu->halt_cond = g_malloc0(sizeof(QemuCond));
>      qemu_cond_init(cpu->halt_cond);
> -    qemu_thread_create(cpu->thread, qemu_kvm_cpu_thread_fn, cpu,
> -                       QEMU_THREAD_JOINABLE);
> +    snprintf(thread_name, TMP_THREAD_NAME_LEN, "CPU %d/KVM",
> +             cpu->cpu_index);
> +    qemu_thread_create(cpu->thread, thread_name, qemu_kvm_cpu_thread_fn,
> +                       cpu, QEMU_THREAD_JOINABLE);
>      while (!cpu->created) {
>          qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
>      }
> @@ -1154,10 +1165,14 @@ static void qemu_kvm_start_vcpu(CPUState *cpu)
>  
>  static void qemu_dummy_start_vcpu(CPUState *cpu)
>  {
> +    char thread_name[TMP_THREAD_NAME_LEN];
> +
>      cpu->thread = g_malloc0(sizeof(QemuThread));
>      cpu->halt_cond = g_malloc0(sizeof(QemuCond));
>      qemu_cond_init(cpu->halt_cond);
> -    qemu_thread_create(cpu->thread, qemu_dummy_cpu_thread_fn, cpu,
> +    snprintf(thread_name, TMP_THREAD_NAME_LEN, "CPU %d/DUMMY",
> +             cpu->cpu_index);
> +    qemu_thread_create(cpu->thread, thread_name, qemu_dummy_cpu_thread_fn, cpu,
>                         QEMU_THREAD_JOINABLE);
>      while (!cpu->created) {
>          qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 456d437..980a684 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -358,7 +358,7 @@ static void start_data_plane_bh(void *opaque)
>  
>      qemu_bh_delete(s->start_bh);
>      s->start_bh = NULL;
> -    qemu_thread_create(&s->thread, data_plane_thread,
> +    qemu_thread_create(&s->thread, "data_plane", data_plane_thread,
>                         s, QEMU_THREAD_JOINABLE);
>  }

Don't really want to suggest feature creep, but since we can have
several dataplane threads as well, I suggest appending the serial number
of the virtio-blk device, s->blk->serial (can be NULL). Example for
access is in do_get_id_cmd(). Of course with this free-form string,
g_strdup_printf() becomes more attractive.

>  
> diff --git a/hw/usb/ccid-card-emulated.c b/hw/usb/ccid-card-emulated.c
> index aa913df..7213c89 100644
> --- a/hw/usb/ccid-card-emulated.c
> +++ b/hw/usb/ccid-card-emulated.c
> @@ -546,10 +546,10 @@ static int emulated_initfn(CCIDCardState *base)
>          printf("%s: failed to initialize vcard\n", EMULATED_DEV_NAME);
>          return -1;
>      }
> -    qemu_thread_create(&card->event_thread_id, event_thread, card,
> -                       QEMU_THREAD_JOINABLE);
> -    qemu_thread_create(&card->apdu_thread_id, handle_apdu_thread, card,
> -                       QEMU_THREAD_JOINABLE);
> +    qemu_thread_create(&card->event_thread_id, "ccid/event", event_thread,
> +                       card, QEMU_THREAD_JOINABLE);
> +    qemu_thread_create(&card->apdu_thread_id, "ccid/apdu", handle_apdu_thread,
> +                       card, QEMU_THREAD_JOINABLE);
>      return 0;
>  }

No clue how many there can be of these.

>  
> diff --git a/include/qemu/thread.h b/include/qemu/thread.h
> index bf1e110..f7e3b9b 100644
> --- a/include/qemu/thread.h
> +++ b/include/qemu/thread.h
> @@ -52,7 +52,7 @@ void qemu_event_reset(QemuEvent *ev);
>  void qemu_event_wait(QemuEvent *ev);
>  void qemu_event_destroy(QemuEvent *ev);
>  
> -void qemu_thread_create(QemuThread *thread,
> +void qemu_thread_create(QemuThread *thread, const char *name,
>                          void *(*start_routine)(void *),
>                          void *arg, int mode);
>  void *qemu_thread_join(QemuThread *thread);
> diff --git a/libcacard/vscclient.c b/libcacard/vscclient.c
> index 24f7088..3477ab3 100644
> --- a/libcacard/vscclient.c
> +++ b/libcacard/vscclient.c
> @@ -269,7 +269,7 @@ on_host_init(VSCMsgHeader *mhHeader, VSCMsgInit *incoming)
>      send_msg(VSC_ReaderRemove, VSCARD_MINIMAL_READER_ID, NULL, 0);
>      /* launch the event_thread. This will trigger reader adds for all the
>       * existing readers */
> -    qemu_thread_create(&thread_id, event_thread, NULL, 0);
> +    qemu_thread_create(&thread_id, "vsc/event", event_thread, NULL, 0);
>      return 0;
>  }

Ditto.

>  
> diff --git a/migration.c b/migration.c
> index 7235c23..bddec7e 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -679,6 +679,6 @@ void migrate_fd_connect(MigrationState *s)
>      /* Notify before starting migration thread */
>      notifier_list_notify(&migration_state_notifiers, s);
>  
> -    qemu_thread_create(&s->thread, migration_thread, s,
> +    qemu_thread_create(&s->thread, "migration", migration_thread, s,
>                         QEMU_THREAD_JOINABLE);
>  }

At most one such thread at a time, right?

> diff --git a/thread-pool.c b/thread-pool.c
> index 3735fd3..fbdd3ff 100644
> --- a/thread-pool.c
> +++ b/thread-pool.c
> @@ -140,7 +140,7 @@ static void do_spawn_thread(ThreadPool *pool)
>      pool->new_threads--;
>      pool->pending_threads++;
>  
> -    qemu_thread_create(&t, worker_thread, pool, QEMU_THREAD_DETACHED);
> +    qemu_thread_create(&t, "worker", worker_thread, pool, QEMU_THREAD_DETACHED);
>  }

I do think these guys should be numbered somehow. "pending_threads"
looks like an obvious choice, but it might be incorrect.

>  
>  static void spawn_thread_bh_fn(void *opaque)
> diff --git a/ui/vnc-jobs.c b/ui/vnc-jobs.c
> index 2d3fce8..3f3c47b 100644
> --- a/ui/vnc-jobs.c
> +++ b/ui/vnc-jobs.c
> @@ -333,7 +333,8 @@ void vnc_start_worker_thread(void)
>          return ;
>  
>      q = vnc_queue_init();
> -    qemu_thread_create(&q->thread, vnc_worker_thread, q, QEMU_THREAD_DETACHED);
> +    qemu_thread_create(&q->thread, "vnc_worker", vnc_worker_thread, q,
> +                       QEMU_THREAD_DETACHED);
>      queue = q; /* Set global queue */
>  }

Probably one thread only.

>  
> diff --git a/util/compatfd.c b/util/compatfd.c
> index 430a41c..341ada6 100644
> --- a/util/compatfd.c
> +++ b/util/compatfd.c
> @@ -88,7 +88,8 @@ static int qemu_signalfd_compat(const sigset_t *mask)
>      memcpy(&info->mask, mask, sizeof(*mask));
>      info->fd = fds[1];
>  
> -    qemu_thread_create(&thread, sigwait_compat, info, QEMU_THREAD_DETACHED);
> +    qemu_thread_create(&thread, "signalfd_compat", sigwait_compat, info,
> +                       QEMU_THREAD_DETACHED);
>  
>      return fds[0];
>  }

Ditto.

> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index 0fa6c81..45113b4 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -394,8 +394,7 @@ void qemu_event_wait(QemuEvent *ev)
>      }
>  }
>  
> -
> -void qemu_thread_create(QemuThread *thread,
> +void qemu_thread_create(QemuThread *thread, const char *name,
>                         void *(*start_routine)(void*),
>                         void *arg, int mode)
>  {
> @@ -421,6 +420,12 @@ void qemu_thread_create(QemuThread *thread,
>      if (err)
>          error_exit(err, __func__);
>  
> +#ifdef _GNU_SOURCE
> +    if (name_threads) {
> +        pthread_setname_np(thread->thread, name);
> +    }
> +#endif
> +

Maybe a retval check? Or do we ignore ERANGE on purpose?

>      pthread_sigmask(SIG_SETMASK, &oldset, NULL);
>  
>      pthread_attr_destroy(&attr);
> diff --git a/util/qemu-thread-win32.c b/util/qemu-thread-win32.c
> index e42cb77..b9c957b 100644
> --- a/util/qemu-thread-win32.c
> +++ b/util/qemu-thread-win32.c
> @@ -333,7 +333,7 @@ void *qemu_thread_join(QemuThread *thread)
>      return ret;
>  }
>  
> -void qemu_thread_create(QemuThread *thread,
> +void qemu_thread_create(QemuThread *thread, const char *name,
>                         void *(*start_routine)(void *),
>                         void *arg, int mode)
>  {
> 

Anyway this is for helping debugging, and there's nothing in here that
I'd call a bug, so I won't waste your time with asking for a new version. :)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo