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Subject[PATCH 07/24] perf daemon: Add config file change check
Date
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);
}

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