Messages in this thread | | | From | Namhyung Kim <> | Date | Tue, 19 Jan 2021 14:37:42 +0900 | Subject | Re: [PATCH 12/22] perf daemon: Allow only one daemon over base directory |
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On Sun, Jan 3, 2021 at 7:05 AM Jiri Olsa <jolsa@kernel.org> wrote: > > Add 'lock' file under daemon base and flock it, so only one > perf daemon can run on top of it. > > Example: > > # cat ~/.perfconfig > [daemon] > base=/opt/perfdata > > [session-cycles] > run = -m 10M -e cycles --overwrite --switch-output -a > > [session-sched] > run = -m 20M -e sched:* --overwrite --switch-output -a > > Starting the daemon: > > # perf daemon start > > And try once more: > > # perf daemon start > failed: another perf daemon (pid 775594) owns /opt/perfdata > > will end up with an error, because there's already one running > on top of /opt/perfdata. > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > --- > tools/perf/builtin-daemon.c | 49 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 49 insertions(+) > > diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c > index 45748bb471ec..1982eedd3f3f 100644 > --- a/tools/perf/builtin-daemon.c > +++ b/tools/perf/builtin-daemon.c > @@ -8,6 +8,7 @@ > #include <string.h> > #include <sys/types.h> > #include <sys/wait.h> > +#include <sys/file.h> > #include <signal.h> > #include <stdlib.h> > #include <time.h> > @@ -562,12 +563,18 @@ static int cmd_session_list(struct daemon *daemon, union cmd *cmd, FILE *out) > /* output */ > csv_sep, daemon->base, SESSION_OUTPUT); > > + fprintf(out, "%c%s/%s", > + /* lock */ > + csv_sep, daemon->base, "lock"); > + > fprintf(out, "\n"); > } else { > fprintf(out, "[%d:daemon] base: %s\n", getpid(), daemon->base); > if (cmd->list.verbose) { > fprintf(out, " output: %s/%s\n", > daemon->base, SESSION_OUTPUT); > + fprintf(out, " lock: %s/lock\n", > + daemon->base); > } > } > > @@ -761,6 +768,42 @@ static int handle_config_changes(struct daemon *daemon, int conf_fd, > return 0; > } > > +static int check_lock(struct daemon *daemon) > +{ > + char path[PATH_MAX]; > + char buf[20]; > + int fd, pid; > + ssize_t len; > + > + scnprintf(path, sizeof(path), "%s/lock", daemon->base); > + > + fd = open(path, O_RDWR|O_CREAT|O_CLOEXEC, 0640); > + if (fd < 0) > + return -1; > + > + if (lockf(fd, F_TLOCK, 0) < 0) { > + filename__read_int(path, &pid); > + fprintf(stderr, "failed: another perf daemon (pid %d) owns %s\n", > + pid, daemon->base); > + return -1; > + }
So the fd is (a kind of) leaked and the lock is released only when the daemon is going to die, right?
Thanks, Namhyung
> + > + scnprintf(buf, sizeof(buf), "%d", getpid()); > + len = strlen(buf); > + > + if (write(fd, buf, len) != len) { > + perror("write failed"); > + return -1; > + } > + > + if (ftruncate(fd, len)) { > + perror("ftruncate failed"); > + return -1; > + } > + > + return 0; > +} > + > static int go_background(struct daemon *daemon) > { > int pid, fd; > @@ -775,6 +818,9 @@ static int go_background(struct daemon *daemon) > if (setsid() < 0) > return -1; > > + if (check_lock(daemon)) > + return -1; > + > umask(0); > > if (chdir(daemon->base)) { > @@ -861,6 +907,9 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[], > if (setup_server_config(daemon)) > return -1; > > + if (foreground && check_lock(daemon)) > + return -1; > + > if (!foreground && go_background(daemon)) > return -1; > > -- > 2.26.2 >
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