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perf daemon: Add signalfd support
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Use a signalfd fd to track SIGCHLD signals as notifications for perf
session termination.

This way we don't need to actively check for child status, being
notified if there's change.

Suggested-by: Alexei Budankov <abudankov@huawei.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210208200908.1019149-10-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Jiri Olsa authored and Arnaldo Carvalho de Melo committed Feb 11, 2021
1 parent 88adb11 commit 12c1a41
Showing 1 changed file with 155 additions and 6 deletions.
161 changes: 155 additions & 6 deletions tools/perf/builtin-daemon.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
#include <string.h>
#include <signal.h>
#include <stdlib.h>
#include <time.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
Expand All @@ -18,6 +19,8 @@
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.h>
#include <sys/signalfd.h>
#include <sys/wait.h>
#include <poll.h>
#include <sys/stat.h>
#include "builtin.h"
Expand Down Expand Up @@ -83,6 +86,7 @@ struct daemon {
struct list_head sessions;
FILE *out;
char perf[PATH_MAX];
int signal_fd;
};

static struct daemon __daemon = {
Expand Down Expand Up @@ -368,6 +372,116 @@ static int daemon_session__run(struct daemon_session *session,
return -1;
}

static pid_t handle_signalfd(struct daemon *daemon)
{
struct daemon_session *session;
struct signalfd_siginfo si;
ssize_t err;
int status;
pid_t pid;

err = read(daemon->signal_fd, &si, sizeof(struct signalfd_siginfo));
if (err != sizeof(struct signalfd_siginfo))
return -1;

list_for_each_entry(session, &daemon->sessions, list) {

if (session->pid != (int) si.ssi_pid)
continue;

pid = waitpid(session->pid, &status, 0);
if (pid == session->pid) {
if (WIFEXITED(status)) {
pr_info("session '%s' exited, status=%d\n",
session->name, WEXITSTATUS(status));
} else if (WIFSIGNALED(status)) {
pr_info("session '%s' killed (signal %d)\n",
session->name, WTERMSIG(status));
} else if (WIFSTOPPED(status)) {
pr_info("session '%s' stopped (signal %d)\n",
session->name, WSTOPSIG(status));
} else {
pr_info("session '%s' Unexpected status (0x%x)\n",
session->name, status);
}
}

session->state = KILL;
session->pid = -1;
return pid;
}

return 0;
}

static int daemon_session__wait(struct daemon_session *session, struct daemon *daemon,
int secs)
{
struct pollfd pollfd = {
.fd = daemon->signal_fd,
.events = POLLIN,
};
pid_t wpid = 0, pid = session->pid;
time_t start;

start = time(NULL);

do {
int err = poll(&pollfd, 1, 1000);

if (err > 0) {
wpid = handle_signalfd(daemon);
} else if (err < 0) {
perror("failed: poll\n");
return -1;
}

if (start + secs < time(NULL))
return -1;
} while (wpid != pid);

return 0;
}

static bool daemon__has_alive_session(struct daemon *daemon)
{
struct daemon_session *session;

list_for_each_entry(session, &daemon->sessions, list) {
if (session->pid != -1)
return true;
}

return false;
}

static int daemon__wait(struct daemon *daemon, int secs)
{
struct pollfd pollfd = {
.fd = daemon->signal_fd,
.events = POLLIN,
};
time_t start;

start = time(NULL);

do {
int err = poll(&pollfd, 1, 1000);

if (err > 0) {
handle_signalfd(daemon);
} else if (err < 0) {
perror("failed: poll\n");
return -1;
}

if (start + secs < time(NULL))
return -1;
} while (daemon__has_alive_session(daemon));

return 0;
}

static int setup_server_socket(struct daemon *daemon)
{
struct sockaddr_un addr;
Expand Down Expand Up @@ -493,9 +607,14 @@ static int daemon_session__signal(struct daemon_session *session, int sig)
return kill(session->pid, sig);
}

static void daemon_session__kill(struct daemon_session *session)
static void daemon_session__kill(struct daemon_session *session,
struct daemon *daemon)
{
daemon_session__signal(session, SIGTERM);
if (daemon_session__wait(session, daemon, 10)) {
daemon_session__signal(session, SIGKILL);
daemon_session__wait(session, daemon, 10);
}
}

static void daemon__signal(struct daemon *daemon, int sig)
Expand Down Expand Up @@ -523,6 +642,10 @@ static void daemon_session__remove(struct daemon_session *session)
static void daemon__kill(struct daemon *daemon)
{
daemon__signal(daemon, SIGTERM);
if (daemon__wait(daemon, 10)) {
daemon__signal(daemon, SIGKILL);
daemon__wait(daemon, 10);
}
}

static void daemon__exit(struct daemon *daemon)
Expand All @@ -549,7 +672,7 @@ static int daemon__reconfig(struct daemon *daemon)
/* Remove session. */
if (session->state == KILL) {
if (session->pid > 0) {
daemon_session__kill(session);
daemon_session__kill(session, daemon);
pr_info("reconfig: session '%s' killed\n", session->name);
}
daemon_session__remove(session);
Expand All @@ -558,7 +681,7 @@ static int daemon__reconfig(struct daemon *daemon)

/* Reconfig session. */
if (session->pid > 0) {
daemon_session__kill(session);
daemon_session__kill(session, daemon);
pr_info("reconfig: session '%s' killed\n", session->name);
}
if (daemon_session__run(session, daemon))
Expand Down Expand Up @@ -724,6 +847,20 @@ static int go_background(struct daemon *daemon)
return 0;
}

static int setup_signalfd(struct daemon *daemon)
{
sigset_t mask;

sigemptyset(&mask);
sigaddset(&mask, SIGCHLD);

if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1)
return -1;

daemon->signal_fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC);
return daemon->signal_fd;
}

static int __cmd_start(struct daemon *daemon, struct option parent_options[],
int argc, const char **argv)
{
Expand All @@ -733,8 +870,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
OPT_PARENT(parent_options),
OPT_END()
};
int sock_fd = -1, conf_fd = -1;
int sock_pos, file_pos;
int sock_fd = -1, conf_fd = -1, signal_fd = -1;
int sock_pos, file_pos, signal_pos;
struct fdarray fda;
int err = 0;

Expand Down Expand Up @@ -766,7 +903,7 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],

pr_info("daemon started (pid %d)\n", getpid());

fdarray__init(&fda, 2);
fdarray__init(&fda, 3);

sock_fd = setup_server_socket(daemon);
if (sock_fd < 0)
Expand All @@ -776,6 +913,10 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
if (conf_fd < 0)
goto out;

signal_fd = setup_signalfd(daemon);
if (signal_fd < 0)
goto out;

sock_pos = fdarray__add(&fda, sock_fd, POLLIN|POLLERR|POLLHUP, 0);
if (sock_pos < 0)
goto out;
Expand All @@ -784,6 +925,10 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
if (file_pos < 0)
goto out;

signal_pos = fdarray__add(&fda, signal_fd, POLLIN|POLLERR|POLLHUP, 0);
if (signal_pos < 0)
goto out;

signal(SIGINT, sig_handler);
signal(SIGTERM, sig_handler);

Expand All @@ -797,6 +942,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
err = handle_server_socket(daemon, sock_fd);
if (fda.entries[file_pos].revents & POLLIN)
err = handle_config_changes(daemon, conf_fd, &reconfig);
if (fda.entries[signal_pos].revents & POLLIN)
err = handle_signalfd(daemon) < 0;

if (reconfig)
err = setup_server_config(daemon);
Expand All @@ -813,6 +960,8 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
close(sock_fd);
if (conf_fd != -1)
close(conf_fd);
if (conf_fd != -1)
close(signal_fd);

pr_info("daemon exited\n");
fclose(daemon->out);
Expand Down

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