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Re: [Qemu-devel] [PATCH v12 19/21] migration: Wait for blocking IO
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v12 19/21] migration: Wait for blocking IO |
Date: |
Thu, 3 May 2018 16:04:06 +0100 |
User-agent: |
Mutt/1.9.5 (2018-04-13) |
* Juan Quintela (address@hidden) wrote:
> We have three conditions here:
> - channel fails -> error
> - we have to quit: we close the channel and reads fails
> - normal read that success, we are in bussiness
>
> So forget the complications of waiting in a semaphore.
>
> Signed-off-by: Juan Quintela <address@hidden>
I *think* this is OK; but I'd prefer to see most of this folded into
earlier patches where I think they'd be cleaner rather than putting
stuff in and shuffling it around.
Dave
> ---
> migration/ram.c | 81 ++++++++++++++++++-------------------------------
> 1 file changed, 29 insertions(+), 52 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 9adbaa81f9..2734f91ded 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -496,8 +496,6 @@ typedef struct {
> bool running;
> /* should this thread finish */
> bool quit;
> - /* thread has work to do */
> - bool pending_job;
> /* array of pages to receive */
> MultiFDPages_t *pages;
> /* packet allocated len */
> @@ -1056,14 +1054,6 @@ static void multifd_recv_sync_main(void)
> for (i = 0; i < migrate_multifd_channels(); i++) {
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> - trace_multifd_recv_sync_main_signal(p->id);
> - qemu_mutex_lock(&p->mutex);
> - p->pending_job = true;
> - qemu_mutex_unlock(&p->mutex);
> - }
> - for (i = 0; i < migrate_multifd_channels(); i++) {
> - MultiFDRecvParams *p = &multifd_recv_state->params[i];
> -
> trace_multifd_recv_sync_main_wait(p->id);
> qemu_sem_wait(&multifd_recv_state->sem_sync);
> qemu_mutex_lock(&p->mutex);
> @@ -1076,7 +1066,6 @@ static void multifd_recv_sync_main(void)
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> trace_multifd_recv_sync_main_signal(p->id);
> -
> qemu_sem_post(&p->sem_sync);
> }
> trace_multifd_recv_sync_main(multifd_recv_state->seq);
> @@ -1091,51 +1080,40 @@ static void *multifd_recv_thread(void *opaque)
> trace_multifd_recv_thread_start(p->id);
>
> while (true) {
> + uint32_t used;
> + uint32_t flags;
> +
> + ret = qio_channel_read_all_eof(p->c, (void *)p->packet,
> + p->packet_len, &local_err);
> + if (ret == 0) { /* EOF */
> + break;
> + }
> + if (ret == -1) { /* Error */
> + break;
> + }
> +
> qemu_mutex_lock(&p->mutex);
> - if (true || p->pending_job) {
> - uint32_t used;
> - uint32_t flags;
> - qemu_mutex_unlock(&p->mutex);
> -
> - ret = qio_channel_read_all_eof(p->c, (void *)p->packet,
> - p->packet_len, &local_err);
> - if (ret == 0) { /* EOF */
> - break;
> - }
> - if (ret == -1) { /* Error */
> - break;
> - }
> -
> - qemu_mutex_lock(&p->mutex);
> - ret = multifd_recv_unfill_packet(p, &local_err);
> - if (ret) {
> - qemu_mutex_unlock(&p->mutex);
> - break;
> - }
> -
> - used = p->pages->used;
> - flags = p->flags;
> - trace_multifd_recv(p->id, p->seq, used, flags);
> - p->pending_job = false;
> - p->num_packets++;
> - p->num_pages += used;
> + ret = multifd_recv_unfill_packet(p, &local_err);
> + if (ret) {
> qemu_mutex_unlock(&p->mutex);
> + break;
> + }
>
> - ret = qio_channel_readv_all(p->c, p->pages->iov, used,
> &local_err);
> - if (ret != 0) {
> - break;
> - }
> + used = p->pages->used;
> + flags = p->flags;
> + trace_multifd_recv(p->id, p->seq, used, flags);
> + p->num_packets++;
> + p->num_pages += used;
> + qemu_mutex_unlock(&p->mutex);
>
> - if (flags & MULTIFD_FLAG_SYNC) {
> - qemu_sem_post(&multifd_recv_state->sem_sync);
> - qemu_sem_wait(&p->sem_sync);
> - }
> - } else if (p->quit) {
> - qemu_mutex_unlock(&p->mutex);
> + ret = qio_channel_readv_all(p->c, p->pages->iov, used, &local_err);
> + if (ret != 0) {
> break;
> - } else {
> - qemu_mutex_unlock(&p->mutex);
> - /* sometimes there are spurious wakeups */
> + }
> +
> + if (flags & MULTIFD_FLAG_SYNC) {
> + qemu_sem_post(&multifd_recv_state->sem_sync);
> + qemu_sem_wait(&p->sem_sync);
> }
> }
>
> @@ -1173,7 +1151,6 @@ int multifd_load_setup(void)
> qemu_sem_init(&p->sem, 0);
> qemu_sem_init(&p->sem_sync, 0);
> p->quit = false;
> - p->pending_job = false;
> p->id = i;
> multifd_pages_init(&p->pages, page_count);
> p->packet_len = sizeof(MultiFDPacket_t)
> --
> 2.17.0
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
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