Re: [PATCH 07/24] perf daemon: Add config file change check

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Sun, Jan 31, 2021 at 12:48:39AM +0100, Jiri Olsa escreveu:
> Adding support to detect daemon's config file changes
> and re-read the configuration when that happens.
> 
> Using inotify file descriptor pluged into the main
> fdarray object for polling.
> 
> Example:
> 
>   # cat ~/.perfconfig
>   [daemon]
>   base=/opt/perfdata
> 
>   [session-cycles]
>   run = -m 10M -e cycles --overwrite --switch-output -a
> 
> Starting the daemon:
> 
>   # perf daemon start
> 
> Check sessions:
> 
>   # perf daemon
>   [772262:daemon] base: /opt/perfdata
>   [772263:cycles] perf record -m 10M -e cycles --overwrite --switch-output -a
> 
> Change '-m 10M' to '-m 20M', and check daemon log:
> 
>   # tail -f /opt/perfdata/output
>   [2021-01-02 20:31:41.234045] daemon started (pid 772262)
>   [2021-01-02 20:31:41.235072] reconfig: ruining session [cycles:772263]: -m 10M -e cycles --overwrite --switch-output -a
>   [2021-01-02 20:32:08.310137] reconfig: session 'cycles' killed
>   [2021-01-02 20:32:08.310847] reconfig: ruining session [cycles:772338]: -m 20M -e cycles --overwrite --switch-output -a
> 
> And the session list:
> 
>   # perf daemon
>   [772262:daemon] base: /opt/perfdata
>   [772338:cycles] perf record -m 20M -e cycles --overwrite --switch-output -a
> 
> Note the changed '-m 20M' option is in place.
> 
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/perf/builtin-daemon.c | 99 +++++++++++++++++++++++++++++++++++--
>  1 file changed, 96 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
> index be2ade9967b3..d0a0a998e073 100644
> --- a/tools/perf/builtin-daemon.c
> +++ b/tools/perf/builtin-daemon.c
> @@ -10,6 +10,8 @@
>  #include <stdio.h>
>  #include <unistd.h>
>  #include <errno.h>
> +#include <sys/inotify.h>
> +#include <libgen.h>
>  #include <sys/types.h>
>  #include <sys/socket.h>
>  #include <sys/un.h>
> @@ -73,6 +75,7 @@ struct session {
>  struct daemon {
>  	const char		*config;
>  	char			*config_real;
> +	char			*config_base;
>  	const char		*base_user;
>  	char			*base;
>  	struct list_head	 sessions;
> @@ -493,6 +496,7 @@ static void daemon__free(struct daemon *daemon)
>  		session__remove(session);
>  
>  	free(daemon->config_real);
> +	free(daemon->config_base);
>  	free(daemon->base);

Please replace those with zfree()

>  }
>  
> @@ -535,6 +539,83 @@ static int daemon__reconfig(struct daemon *daemon)
>  	return 0;
>  }
>  
> +static int setup_config_changes(struct daemon *daemon)
> +{
> +	char *basen = strdup(daemon->config_real);
> +	char *dirn  = strdup(daemon->config_real);
> +	char *base, *dir;
> +	int fd, wd;
> +
> +	if (!dirn || !basen)
> +		return -ENOMEM;

This may leak one of them

> +
> +	fd = inotify_init1(IN_NONBLOCK|O_CLOEXEC);
> +	if (fd < 0) {
> +		perror("failed: inotify_init");
> +		return -1;
> +	}

Cool that inotify is being used here :-)

> +
> +	dir = dirname(dirn);
> +	base = basename(basen);
> +	pr_debug("config file: %s, dir: %s\n", base, dir);
> +
> +	wd = inotify_add_watch(fd, dir, IN_CLOSE_WRITE);
> +	if (wd >= 0) {
> +		daemon->config_base = strdup(base);
> +		if (!daemon->config_base) {
> +			close(fd);
> +			wd = -1;
> +		}
> +	} else {
> +		perror("failed: inotify_add_watch");
> +	}
> +
> +	free(basen);
> +	free(dirn);
> +	return wd < 0 ? -1 : fd;
> +}
> +
> +static bool process_inotify_event(struct daemon *daemon, char *buf, ssize_t len)
> +{
> +	char *p = buf;
> +
> +	while (p < (buf + len)) {
> +		struct inotify_event *event = (struct inotify_event *) p;
> +
> +		/*
> +		 * We monitor config directory, check if our
> +		 * config file was changes.
> +		 */
> +		if ((event->mask & IN_CLOSE_WRITE) &&
> +		    !(event->mask & IN_ISDIR)) {
> +			if (!strcmp(event->name, daemon->config_base))
> +				return true;
> +		}
> +		p += sizeof(*event) + event->len;
> +	}
> +	return false;
> +}
> +
> +static int handle_config_changes(struct daemon *daemon, int conf_fd,
> +				 bool *config_changed)
> +{
> +	char buf[4096];
> +	ssize_t len;
> +
> +	while (!(*config_changed)) {
> +		len = read(conf_fd, buf, sizeof(buf));
> +		if (len == -1) {
> +			if (errno != EAGAIN) {
> +				perror("failed: read");
> +				return -1;
> +			}
> +			return 0;
> +		}
> +		*config_changed = process_inotify_event(daemon, buf, len);
> +	}
> +	return 0;
> +}
> +
>  static int setup_config(struct daemon *daemon)
>  {
>  	if (daemon->base_user) {
> @@ -569,8 +650,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
>  		OPT_PARENT(parent_options),
>  		OPT_END()
>  	};
> -	int sock_fd = -1;
> -	int sock_pos;
> +	int sock_fd = -1, conf_fd = -1;
> +	int sock_pos, file_pos;
>  	struct fdarray fda;
>  	int err = 0;
>  
> @@ -591,16 +672,24 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
>  
>  	pr_info("daemon started (pid %d)\n", getpid());
>  
> -	fdarray__init(&fda, 1);
> +	fdarray__init(&fda, 2);
>  
>  	sock_fd = setup_server_socket(daemon);
>  	if (sock_fd < 0)
>  		goto out;
>  
> +	conf_fd = setup_config_changes(daemon);
> +	if (conf_fd < 0)
> +		goto out;
> +
>  	sock_pos = fdarray__add(&fda, sock_fd, POLLIN|POLLERR|POLLHUP, 0);
>  	if (sock_pos < 0)
>  		goto out;
>  
> +	file_pos = fdarray__add(&fda, conf_fd, POLLIN|POLLERR|POLLHUP, 0);
> +	if (file_pos < 0)
> +		goto out;
> +
>  	signal(SIGINT, sig_handler);
>  	signal(SIGTERM, sig_handler);
>  
> @@ -612,6 +701,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
>  
>  			if (fda.entries[sock_pos].revents & POLLIN)
>  				err = handle_server_socket(daemon, sock_fd);
> +			if (fda.entries[file_pos].revents & POLLIN)
> +				err = handle_config_changes(daemon, conf_fd, &reconfig);
>  
>  			if (reconfig)
>  				err = setup_server_config(daemon);
> @@ -625,6 +716,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
>  
>  	if (sock_fd != -1)
>  		close(sock_fd);
> +	if (conf_fd != -1)
> +		close(conf_fd);
>  
>  	pr_info("daemon exited\n");
>  	fclose(daemon->out);
> -- 
> 2.29.2
> 

-- 

- Arnaldo