diff options
author | Avidan Borisov <avidanborisov@gmail.com> | 2023-06-26 12:16:32 +0300 |
---|---|---|
committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2023-10-17 18:33:27 -0400 |
commit | a3929b09b4f650e27d62c9602093936db5fca48a (patch) | |
tree | 8b0c6e74847f3a2f2dae76e1bc8f508d9b64b18e | |
parent | 354dccca52e805ce1b22e2b62cbae8c265886c27 (diff) | |
download | trace-cmd-a3929b09b4f650e27d62c9602093936db5fca48a.tar.gz |
trace-cmd record: Add --daemonize
Add a --daemonize flag to trace-cmd record which allows the user to record
in the background, after tracing has completely initialized.
Link: https://lore.kernel.org/linux-trace-devel/20230626091635.3002827-2-avidanborisov@gmail.com
Signed-off-by: Avidan Borisov <avidanborisov@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
-rw-r--r-- | Documentation/trace-cmd/trace-cmd-record.1.txt | 3 | ||||
-rw-r--r-- | tracecmd/trace-record.c | 129 | ||||
-rw-r--r-- | tracecmd/trace-usage.c | 1 |
3 files changed, 131 insertions, 2 deletions
diff --git a/Documentation/trace-cmd/trace-cmd-record.1.txt b/Documentation/trace-cmd/trace-cmd-record.1.txt index b709e483..366ab464 100644 --- a/Documentation/trace-cmd/trace-cmd-record.1.txt +++ b/Documentation/trace-cmd/trace-cmd-record.1.txt @@ -418,6 +418,9 @@ OPTIONS run on a privileged guest that the host is aware of (as denoted by the 'cid' in the *-P* option for the agent). +*--daemonize* + Run trace-cmd in the background as a daemon after recording has started. + EXAMPLES -------- diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c index bced8040..0049768d 100644 --- a/tracecmd/trace-record.c +++ b/tracecmd/trace-record.c @@ -91,6 +91,8 @@ static bool quiet; static bool fork_process; +static bool do_daemonize; + /* Max size to let a per cpu file get */ static int max_kb; @@ -1634,6 +1636,109 @@ static inline void ptrace_attach(struct buffer_instance *instance, int pid) { } #endif /* NO_PTRACE */ +static bool child_detached; + +static void daemonize_set_child_detached(int s) +{ + child_detached = true; +} + +static void daemonize_start(void) +{ + int devnull; + int status; + int pid; + int rc; + + pid = fork(); + if (pid == -1) + die("daemonize: fork failed"); + + if (pid == 0) { /* child */ + /* + * We keep stdout and stderr open to allow the user to + * see output and errors after the daemonization (the user can + * choose to supress it with >/dev/null if the user wants). + * + * No reason to keep stdin open (it might interfere with the + * shell), we redirect it to /dev/null. + */ + devnull = open("/dev/null", O_RDONLY); + if (devnull == -1) + die("daemonize: open /dev/null failed"); + + if (devnull > 0) { + if (dup2(devnull, 0) == -1) + die("daemonize: dup2"); + close(0); + } + + return; + + /* + * The child returns to back to the caller, but the parent waits until + * SIGRTMIN is received from the child (by calling daemonize_finish()), + * or the child exits for some reason (usually an indication of + * an error), which ever comes first. + * + * Then the parent exits (with the status code of the child, + * if it finished early, or with 0 if SIGRTMIN was received), + * which causes the child (and its entire process tree) to be + * inherited by init. + * + * Note that until the child calls daemonize_finish(), it still has + * the same session id as the parent, so it can die together with + * the parent before daemonization finished (purposefully, since the + * user might send a quick Ctrl^C to cancel the command, and we don't + * want background processes staying alive in that case) + */ + } else { /* parent */ + struct sigaction sa = { + /* disable SA_RESTART, to allow waitpid() to be interrupted by SIGRTMIN */ + .sa_flags = 0, + .sa_handler = daemonize_set_child_detached + }; + + if (sigemptyset(&sa.sa_mask) == -1) + die("daemonize: sigemptyset failed"); + + if (sigaddset(&sa.sa_mask, SIGRTMIN) == -1) + die("daemonize: sigaddset failed"); + + if (sigprocmask(SIG_UNBLOCK, &sa.sa_mask, NULL) == -1) + die("daemonize: sigprocmask failed"); + + if (sigaction(SIGRTMIN, &sa, NULL) == -1) + die("daemonize: sigaction failed"); + + do { + rc = waitpid(pid, &status, 0); + } while (!child_detached && ((rc == -1) && (errno == EINTR))); + + if (child_detached) + exit(0); + else if (rc == pid) + exit(WIFEXITED(status)); + else + die("daemonize: waitpid failed"); + + __builtin_unreachable(); + } +} + +static void daemonize_finish(void) +{ + /* + * setsid() will also set the sid to be the pgid to all currently + * running threads in the process group (such as the tsync thread). + */ + if (setsid() == -1) + die("daemonize: setsid"); + + if (kill(getppid(), SIGRTMIN) == -1) + die("daemonize: kill"); +} + static void trace_or_sleep(enum trace_type type, bool pwait) { int i; @@ -1748,6 +1853,9 @@ static void run_cmd(enum trace_type type, const char *user, int argc, char **arg execute_program(argc, argv); } + + if (do_daemonize) + daemonize_finish(); if (fork_process) exit(0); if (do_ptrace) { @@ -5790,6 +5898,7 @@ enum { OPT_proxy = 261, OPT_temp = 262, OPT_notimeout = 264, + OPT_daemonize = 265, }; void trace_stop(int argc, char **argv) @@ -6217,6 +6326,7 @@ static void parse_record_options(int argc, {"file-version", required_argument, NULL, OPT_file_ver}, {"proxy", required_argument, NULL, OPT_proxy}, {"temp", required_argument, NULL, OPT_temp}, + {"daemonize", no_argument, NULL, OPT_daemonize}, {NULL, 0, NULL, 0} }; @@ -6690,6 +6800,11 @@ static void parse_record_options(int argc, die("--fork option used for 'start' command only"); fork_process = true; break; + case OPT_daemonize: + if (!IS_RECORD(ctx)) + die("--daemonize option used for 'record' command only"); + do_daemonize = true; + break; case OPT_tsc2nsec: ret = get_tsc_nsec(&ctx->tsc2nsec.shift, &ctx->tsc2nsec.mult); @@ -6933,6 +7048,9 @@ static void record_trace(int argc, char **argv, struct buffer_instance *instance; struct filter_pids *pid; + if (do_daemonize) + daemonize_start(); + /* * If top_instance doesn't have any plugins or events, then * remove it from being processed. @@ -7051,8 +7169,15 @@ static void record_trace(int argc, char **argv, } } } - /* sleep till we are woken with Ctrl^C */ - printf("Hit Ctrl^C to stop recording\n"); + + if (do_daemonize) { + daemonize_finish(); + printf("Send SIGINT to pid %d to stop recording\n", getpid()); + } else { + /* sleep till we are woken with Ctrl^C */ + printf("Hit Ctrl^C to stop recording\n"); + } + for_all_instances(instance) { /* If an instance is not tracing individual processes * or there is an error while waiting for a process to diff --git a/tracecmd/trace-usage.c b/tracecmd/trace-usage.c index ecb7cad1..45cb4f04 100644 --- a/tracecmd/trace-usage.c +++ b/tracecmd/trace-usage.c @@ -81,6 +81,7 @@ static struct usage_help usage_help[] = { " available algorithms can be listed with trace-cmd list -c\n" " --proxy vsocket to reach the agent. Acts the same as -A (for an agent)\n" " but will send the proxy connection to the agent.\n" + " --daemonize run trace-cmd in the background as a daemon after recording has started\n" }, { "set", |