perf daemon: Add background support

Add support to put the daemon process in the background.

It's now enabled by default and -f option is added to keep the daemon
process on the console for debugging.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.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/20210208200908.1019149-9-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/perf-daemon.txt b/tools/perf/Documentation/perf-daemon.txt
index 173b3f9..af5916d 100644 (file)
--- a/tools/perf/Documentation/perf-daemon.txt
+++ b/tools/perf/Documentation/perf-daemon.txt
@@ -56,6 +56,10 @@ START COMMAND
 -------------
 The start command creates the daemon process.
 
+-f::
+--foreground::
+       Do not put the process in background.
+
 
 CONFIG FILE
 -----------

diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
index f33fc5c..2241d0e 100644 (file)
--- a/tools/perf/builtin-daemon.c
+++ b/tools/perf/builtin-daemon.c
@@ -675,10 +675,61 @@ static int setup_config(struct daemon *daemon)
        return daemon->config_real ? 0 : -1;
 }
 
+static int go_background(struct daemon *daemon)
+{
+       int pid, fd;
+
+       pid = fork();
+       if (pid < 0)
+               return -1;
+
+       if (pid > 0)
+               return 1;
+
+       if (setsid() < 0)
+               return -1;
+
+       umask(0);
+
+       if (chdir(daemon->base)) {
+               perror("failed: chdir");
+               return -1;
+       }
+
+       fd = open("output", O_RDWR|O_CREAT|O_TRUNC, 0644);
+       if (fd < 0) {
+               perror("failed: open");
+               return -1;
+       }
+
+       if (fcntl(fd, F_SETFD, FD_CLOEXEC)) {
+               perror("failed: fcntl FD_CLOEXEC");
+               close(fd);
+               return -1;
+       }
+
+       close(0);
+       dup2(fd, 1);
+       dup2(fd, 2);
+       close(fd);
+
+       daemon->out = fdopen(1, "w");
+       if (!daemon->out) {
+               close(1);
+               close(2);
+               return -1;
+       }
+
+       setbuf(daemon->out, NULL);
+       return 0;
+}
+
 static int __cmd_start(struct daemon *daemon, struct option parent_options[],
                       int argc, const char **argv)
 {
+       bool foreground = false;
        struct option start_options[] = {
+               OPT_BOOLEAN('f', "foreground", &foreground, "stay on console"),
                OPT_PARENT(parent_options),
                OPT_END()
        };
@@ -699,6 +750,17 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
        if (setup_server_config(daemon))
                return -1;
 
+       if (!foreground) {
+               err = go_background(daemon);
+               if (err) {
+                       /* original process, exit normally */
+                       if (err == 1)
+                               err = 0;
+                       daemon__exit(daemon);
+                       return err;
+               }
+       }
+
        debug_set_file(daemon->out);
        debug_set_display_time(true);