* Juan Quintela (quint...@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote:
> > * Juan Quintela (quint...@redhat.com) wrote:
> >> "Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote:
> >> > * Juan Quintela (quint...@redhat.com) wrote:
> >> >> "Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote:
> >> >> > * Juan Quintela (quint...@redhat.com) wrote:
> >> >> >> We know quit closing the QIO.
>
> ...
> >> > Two questions from that then:
> >> > a) Are you sure it's safe to close the qio_channel while another
> >> > thread is in qio_channel_read_all_eof? Is it really defined that it
> >> > causes the other thread to exit with an error; close() in some stuff
> >> > frees data structures that the other thread is still reading; that's
> >> > why I've used shutdown(2) in the past rather than close on fd's
> >>
> >> Dunno if it is safe (I think it is), but I agree that shutdown will also
> >> get what I need.
> >>
> >> > b) I don't think your answer explains why it's an object_unref?
> >>
> >> That is the standard way to closing qios to not have to take into
> >> account who have it oppened. See previous paragraph, it is better to
> >> use shutdown, done.
> >
> > OK, great; I suspect it's unsafe because as soon as you do the unref
> > it could free the object; actually you should have a ref from each of
> > the threads to sotp it being freed while they use it.
> >
> > Dave
> >
> >> Thanks, Juan.
> >>
> >> > Dave
> >> >
> >> >> Later, Juan.
> >> > --
> >> > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
> > --
> > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
>
> What do you think about this, to avoid me resend the whole series?
>
> From e03d77de1ca179fa0168cead7c23cfeae57f1787 Mon Sep 17 00:00:00 2001
> From: Juan Quintela <quint...@redhat.com>
> Date: Wed, 18 Apr 2018 00:49:19 +0200
> Subject: [PATCH 17/18] migration: Remove not needed semaphore and quit
>
> We know quit with shutdwon in the QIO.
>
> Signed-off-by: Juan Quintela <quint...@redhat.com>
> --
> Add comment
> Use shutdown() instead of unref()
> ---
> migration/ram.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 2c3a452a7d..be5d26f4cb 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -594,14 +594,10 @@ typedef struct {
> QemuThread thread;
> /* communication channel */
> QIOChannel *c;
> - /* sem where to wait for more work */
> - QemuSemaphore sem;
> /* this mutex protects the following parameters */
> QemuMutex mutex;
> /* is this channel thread running */
> bool running;
> - /* should this thread finish */
> - bool quit;
> /* array of pages to receive */
> MultiFDPages_t *pages;
> /* packet allocated len */
> @@ -1152,8 +1148,11 @@ static void multifd_recv_terminate_threads(Error *err)
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> qemu_mutex_lock(&p->mutex);
> - p->quit = true;
> - qemu_sem_post(&p->sem);
> + /* We could arrive here for two reasons:
> + - normal quit, i.e. everything went fine, just finished
> + - error quit: We close the channels so the channel threads
> + finish the qio_channel_read_all_eof() */
> + qio_channel_shutdown(p->c, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
OK, so with any luck all the threads now exit; do we still have a
close/unref once we're sure they have all exited?
Dave
> qemu_mutex_unlock(&p->mutex);
> }
> }
> @@ -1176,7 +1175,6 @@ int multifd_load_cleanup(Error **errp)
> object_unref(OBJECT(p->c));
> p->c = NULL;
> qemu_mutex_destroy(&p->mutex);
> - qemu_sem_destroy(&p->sem);
> qemu_sem_destroy(&p->sem_sync);
> g_free(p->name);
> p->name = NULL;
> @@ -1299,9 +1297,7 @@ int multifd_load_setup(void)
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> qemu_mutex_init(&p->mutex);
> - qemu_sem_init(&p->sem, 0);
> qemu_sem_init(&p->sem_sync, 0);
> - p->quit = false;
> p->id = i;
> p->pages = multifd_pages_init(page_count);
> p->packet_len = sizeof(MultiFDPacket_t)
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
