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Re: [PATCH 4/4] migration: Make sure that we don't call write() in case
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH 4/4] migration: Make sure that we don't call write() in case of error |
Date: |
Wed, 18 Dec 2019 16:33:01 +0000 |
User-agent: |
Mutt/1.13.0 (2019-11-30) |
* Juan Quintela (address@hidden) wrote:
> If we are exiting due to an error/finish/.... Just don't try to even
> touch the channel with one IO operation.
>
> Signed-off-by: Juan Quintela <address@hidden>
> ---
> migration/ram.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 4b44578e57..909ef6d237 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -1601,6 +1601,12 @@ struct {
> QemuSemaphore channels_ready;
> /* multifd ops */
> MultiFDMethods *ops;
> + /*
> + * Have we already run terminate threads. There is a race when it
> + * happens that we got one error while we are exiting.
> + * We will use atomic operations. Only valid values are 0 and 1.
> + */
> + int exiting;
> } *multifd_send_state;
>
> /*
> @@ -1629,6 +1635,10 @@ static int multifd_send_pages(RAMState *rs)
> MultiFDPages_t *pages = multifd_send_state->pages;
> uint64_t transferred;
>
> + if (atomic_read(&multifd_send_state->exiting)) {
> + return -1;
> + }
> +
> qemu_sem_wait(&multifd_send_state->channels_ready);
> for (i = next_channel;; i = (i + 1) % migrate_multifd_channels()) {
> p = &multifd_send_state->params[i];
> @@ -1710,6 +1720,10 @@ static void multifd_send_terminate_threads(Error *err)
> }
> }
>
> + if (atomic_xchg(&multifd_send_state->exiting, 1)) {
> + return;
> + }
That could do with a comment on it; I think what you're saying is
'don't do send_terminate_threads twice'
With a comment,
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> for (i = 0; i < migrate_multifd_channels(); i++) {
> MultiFDSendParams *p = &multifd_send_state->params[i];
>
> @@ -1824,6 +1838,10 @@ static void *multifd_send_thread(void *opaque)
>
> while (true) {
> qemu_sem_wait(&p->sem);
> +
> + if (atomic_read(&multifd_send_state->exiting)) {
> + break;
> + }
> qemu_mutex_lock(&p->mutex);
>
> if (p->pending_job) {
> @@ -1938,6 +1956,7 @@ int multifd_save_setup(Error **errp)
> multifd_send_state->pages = multifd_pages_init(page_count);
> qemu_sem_init(&multifd_send_state->channels_ready, 0);
> multifd_send_state->ops = multifd_ops[migrate_multifd_method()];
> + atomic_set(&multifd_send_state->exiting, 0);
>
> for (i = 0; i < thread_count; i++) {
> MultiFDSendParams *p = &multifd_send_state->params[i];
> --
> 2.23.0
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK