linux-kernel - Re: [PATCH v3 2/9] perf evlist: implement control command handling functions

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Date:   Wed, 20 May 2020 14:38:07 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/9] perf evlist: implement control command handling
 functions

On Wed, May 13, 2020 at 11:00:02AM +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, &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);
> +			break;
> +		}
> +	} while (1);
> +
> +	pr_debug("Message from ctl_fd: \"%s%s\"\n", cmd_data,
> +		 bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\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;
> +		}

are there more comands comming?

jirka