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Re: [PATCH v2 4/4] migration/rdma: source: poll cm_event from return pat
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v2 4/4] migration/rdma: source: poll cm_event from return path |
Date: |
Tue, 25 May 2021 11:26:46 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
* Li Zhijian (lizhijian@cn.fujitsu.com) wrote:
> source side always blocks if postcopy is only enabled at source side.
> users are not able to cancel this migration in this case.
>
> Let source side have chance to cancel this migration
>
> Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
> ---
> V2: utilize poll to check cm event
> ---
> migration/rdma.c | 42 ++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/migration/rdma.c b/migration/rdma.c
> index d829d08d076..f67e21b4f54 100644
> --- a/migration/rdma.c
> +++ b/migration/rdma.c
> @@ -36,6 +36,7 @@
> #include <rdma/rdma_cma.h>
> #include "trace.h"
> #include "qom/object.h"
> +#include <poll.h>
>
> /*
> * Print and error on both the Monitor and the Log file.
> @@ -2460,7 +2461,36 @@ err_rdma_source_init:
> return -1;
> }
>
> -static int qemu_rdma_connect(RDMAContext *rdma, Error **errp)
> +static int qemu_get_cm_event_timeout(RDMAContext *rdma,
> + struct rdma_cm_event **cm_event,
> + long msec, Error **errp)
> +{
> + int ret;
> + struct pollfd poll_fd = {
> + .fd = rdma->channel->fd,
> + .events = POLLIN,
> + .revents = 0
> + };
> +
> + do {
> + ret = poll(&poll_fd, 1, msec);
> + } while (ret < 0 && errno == EINTR);
> +
> + if (ret == 0) {
> + ERROR(errp, "poll cm event timeout");
> + return -1;
> + } else if (ret < 0) {
> + ERROR(errp, "failed to pull cm event, errno=%i", errno);
Typo: 'poll' - I can fix that.
> + return -1;
> + } else if (poll_fd.revents & POLLIN) {
> + return rdma_get_cm_event(rdma->channel, cm_event);
> + } else {
> + ERROR(errp, "no POLLIN event, revent=%x", poll_fd.revents);
> + return -1;
> + }
> +}
> +
> +static int qemu_rdma_connect(RDMAContext *rdma, Error **errp, bool
> return_path)
> {
> RDMACapabilities cap = {
> .version = RDMA_CONTROL_VERSION_CURRENT,
> @@ -2498,7 +2528,11 @@ static int qemu_rdma_connect(RDMAContext *rdma, Error
> **errp)
> goto err_rdma_source_connect;
> }
>
> - ret = rdma_get_cm_event(rdma->channel, &cm_event);
> + if (return_path) {
> + ret = qemu_get_cm_event_timeout(rdma, &cm_event, 5000, errp);
Fixed timeouts are not a great fix; but I can't think of anything
better; the only alternative would be to register the fd on the main
thread's poll and get it to be called back when the event happened.
But for now;
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> + } else {
> + ret = rdma_get_cm_event(rdma->channel, &cm_event);
> + }
> if (ret) {
> perror("rdma_get_cm_event after rdma_connect");
> ERROR(errp, "connecting to destination!");
> @@ -4111,7 +4145,7 @@ void rdma_start_outgoing_migration(void *opaque,
> }
>
> trace_rdma_start_outgoing_migration_after_rdma_source_init();
> - ret = qemu_rdma_connect(rdma, errp);
> + ret = qemu_rdma_connect(rdma, errp, false);
>
> if (ret) {
> goto err;
> @@ -4132,7 +4166,7 @@ void rdma_start_outgoing_migration(void *opaque,
> goto return_path_err;
> }
>
> - ret = qemu_rdma_connect(rdma_return_path, errp);
> + ret = qemu_rdma_connect(rdma_return_path, errp, true);
>
> if (ret) {
> goto return_path_err;
> --
> 2.30.2
>
>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK