Re: [PATCH v8 03/13] perf evlist: implement control command handling functions

Jiri Olsa
2020-06-23T14:56:24Z

On Wed, Jun 17, 2020 at 11:36:46AM +0300, Alexey Budankov wrote:

SNIP

> +static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
> + char *cmd_data, size_t data_size)
> +{
> + int err;
> + char c;
> + size_t bytes_read = 0;
> +
> + memset(cmd_data, 0, data_size--);
> +
> + do {
> + err = read(evlist->ctl_fd.fd, &c, 1);
> + if (err > 0) {
> + if (c == '\n' || c == '\0')
> + break;
> + cmd_data[bytes_read++] = c;
> + if (bytes_read == data_size)
> + break;
> + } else {
> + if (err == -1)
> + pr_err("Failed to read from ctlfd %d: %m\n", evlist->ctl_fd.fd);
> + break;
> + }
> + } while (1);
> +
> + pr_debug("Message from ctl_fd: \"%s%s\"\n", cmd_data,
> + bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0");

do you want to display the message above only if (err > 0) ?

> +
> + if (err > 0) {
> + if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
> + strlen(EVLIST_CTL_CMD_ENABLE_TAG))) {
> + *cmd = EVLIST_CTL_CMD_ENABLE;
> + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
> + strlen(EVLIST_CTL_CMD_DISABLE_TAG))) {
> + *cmd = EVLIST_CTL_CMD_DISABLE;
> + }
> + }
> +
> + return err;
> +}

SNIP

> + int ctlfd_pos = evlist->ctl_fd.pos;
> + struct pollfd *entries = evlist->core.pollfd.entries;
> +
> + if (ctlfd_pos == -1 || !entries[ctlfd_pos].revents)
> + return 0;
> +
> + if (entries[ctlfd_pos].revents & POLLIN) {
> + err = evlist__ctlfd_recv(evlist, cmd, cmd_data,
> + EVLIST_CTL_CMD_MAX_LEN);
> + if (err > 0) {
> + switch (*cmd) {
> + case EVLIST_CTL_CMD_ENABLE:
> + evlist__enable(evlist);
> + break;
> + case EVLIST_CTL_CMD_DISABLE:
> + evlist__disable(evlist);
> + break;
> + case EVLIST_CTL_CMD_ACK:
> + case EVLIST_CTL_CMD_UNSUPPORTED:
> + default:
> + pr_debug("ctlfd: unsupported %d\n", *cmd);
> + break;
> + }
> + if (!(*cmd == EVLIST_CTL_CMD_ACK || *cmd == EVLIST_CTL_CMD_UNSUPPORTED))
> + evlist__ctlfd_ack(evlist);
> + }
> + }
> +
> + if (entries[ctlfd_pos].revents & (POLLHUP | POLLERR))
> + evlist__finalize_ctlfd(evlist);

should this error be propagated via err?

jirka