| Message ID | 20220303164814.284974-4-hreitz@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qsd: Add --daemonize; and add job quit tests | expand |
On Thu, Mar 03, 2022 at 05:48:13PM +0100, Hanna Reitz wrote: > To implement this, we reuse the existing daemonizing functions from the > system emulator, which mainly do the following: > - Fork off a child process, and set up a pipe between parent and child > - The parent process waits until the child sends a status byte over the > pipe (0 means that the child was set up successfully; anything else > (including errors or EOF) means that the child was not set up > successfully), and then exits with an appropriate exit status > - The child process enters a new session (forking off again), changes > the umask, and will ignore terminal signals from then on > - Once set-up is complete, the child will chdir to /, redirect all > standard I/O streams to /dev/null, and tell the parent that set-up has > been completed successfully > > In contrast to qemu-nbd's --fork implementation, during the set up > phase, error messages are not piped through the parent process. > qemu-nbd mainly does this to detect errors, though (while os_daemonize() > has the child explicitly signal success after set up); because we do not > redirect stderr after forking, error messages continue to appear on > whatever the parent's stderr was (until set up is complete). > > Signed-off-by: Hanna Reitz <hreitz@redhat.com> > --- > docs/tools/qemu-storage-daemon.rst | 7 +++++++ > storage-daemon/qemu-storage-daemon.c | 15 +++++++++++++++ > 2 files changed, 22 insertions(+) > Reviewed-by: Eric Blake <eblake@redhat.com>
Am 03.03.2022 um 17:48 hat Hanna Reitz geschrieben: > To implement this, we reuse the existing daemonizing functions from the > system emulator, which mainly do the following: > - Fork off a child process, and set up a pipe between parent and child > - The parent process waits until the child sends a status byte over the > pipe (0 means that the child was set up successfully; anything else > (including errors or EOF) means that the child was not set up > successfully), and then exits with an appropriate exit status > - The child process enters a new session (forking off again), changes > the umask, and will ignore terminal signals from then on > - Once set-up is complete, the child will chdir to /, redirect all > standard I/O streams to /dev/null, and tell the parent that set-up has > been completed successfully > > In contrast to qemu-nbd's --fork implementation, during the set up > phase, error messages are not piped through the parent process. > qemu-nbd mainly does this to detect errors, though (while os_daemonize() > has the child explicitly signal success after set up); because we do not > redirect stderr after forking, error messages continue to appear on > whatever the parent's stderr was (until set up is complete). > > Signed-off-by: Hanna Reitz <hreitz@redhat.com> > --- > docs/tools/qemu-storage-daemon.rst | 7 +++++++ > storage-daemon/qemu-storage-daemon.c | 15 +++++++++++++++ > 2 files changed, 22 insertions(+) > > diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst > index 878e6a5c5c..8b97592663 100644 > --- a/docs/tools/qemu-storage-daemon.rst > +++ b/docs/tools/qemu-storage-daemon.rst > @@ -154,6 +154,13 @@ Standard options: > created but before accepting connections. The daemon has started successfully > when the pid file is written and clients may begin connecting. > > +.. option:: --daemonize > + > + Daemonize the process. The parent process will exit once startup is complete > + (i.e., after the pid file has been or would have been written) or failure > + occurs. Its exit code reflects whether the child has started up successfully > + or failed to do so. > + > Examples > -------- > Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute > diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c > index b798954edb..9f2c3332bf 100644 > --- a/storage-daemon/qemu-storage-daemon.c > +++ b/storage-daemon/qemu-storage-daemon.c > @@ -137,6 +137,9 @@ static void help(void) > "\n" > " --pidfile <path> write process ID to a file after startup\n" > "\n" > +" --daemonize daemonize the process, and have the parent exit\n" > +" once startup is complete\n" > +"\n" So far the long options in the help text are sorted alphabetically. Do we want to keep this? Kevin
diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst index 878e6a5c5c..8b97592663 100644 --- a/docs/tools/qemu-storage-daemon.rst +++ b/docs/tools/qemu-storage-daemon.rst @@ -154,6 +154,13 @@ Standard options: created but before accepting connections. The daemon has started successfully when the pid file is written and clients may begin connecting. +.. option:: --daemonize + + Daemonize the process. The parent process will exit once startup is complete + (i.e., after the pid file has been or would have been written) or failure + occurs. Its exit code reflects whether the child has started up successfully + or failed to do so. + Examples -------- Launch the daemon with QMP monitor socket ``qmp.sock`` so clients can execute diff --git a/storage-daemon/qemu-storage-daemon.c b/storage-daemon/qemu-storage-daemon.c index b798954edb..9f2c3332bf 100644 --- a/storage-daemon/qemu-storage-daemon.c +++ b/storage-daemon/qemu-storage-daemon.c @@ -137,6 +137,9 @@ static void help(void) "\n" " --pidfile <path> write process ID to a file after startup\n" "\n" +" --daemonize daemonize the process, and have the parent exit\n" +" once startup is complete\n" +"\n" QEMU_HELP_BOTTOM "\n", error_get_progname()); } @@ -144,6 +147,7 @@ QEMU_HELP_BOTTOM "\n", enum { OPTION_BLOCKDEV = 256, OPTION_CHARDEV, + OPTION_DAEMONIZE, OPTION_EXPORT, OPTION_MONITOR, OPTION_NBD_SERVER, @@ -200,6 +204,7 @@ static void process_options(int argc, char *argv[], bool pre_init_pass) static const struct option long_options[] = { {"blockdev", required_argument, NULL, OPTION_BLOCKDEV}, {"chardev", required_argument, NULL, OPTION_CHARDEV}, + {"daemonize", no_argument, NULL, OPTION_DAEMONIZE}, {"export", required_argument, NULL, OPTION_EXPORT}, {"help", no_argument, NULL, 'h'}, {"monitor", required_argument, NULL, OPTION_MONITOR}, @@ -225,6 +230,7 @@ static void process_options(int argc, char *argv[], bool pre_init_pass) c == '?' || c == 'h' || c == 'V' || + c == OPTION_DAEMONIZE || c == OPTION_PIDFILE; /* Process every option only in its respective pass */ @@ -277,6 +283,12 @@ static void process_options(int argc, char *argv[], bool pre_init_pass) qemu_opts_del(opts); break; } + case OPTION_DAEMONIZE: + if (os_set_daemonize(true) < 0) { + error_report("--daemonize not supported in this build"); + exit(EXIT_FAILURE); + } + break; case OPTION_EXPORT: { Visitor *v; @@ -367,6 +379,8 @@ int main(int argc, char *argv[]) process_options(argc, argv, true); + os_daemonize(); + module_call_init(MODULE_INIT_QOM); module_call_init(MODULE_INIT_TRACE); qemu_add_opts(&qemu_trace_opts); @@ -389,6 +403,7 @@ int main(int argc, char *argv[]) * it. */ pid_file_init(); + os_setup_post(); while (!exit_requested) { main_loop_wait(false);
To implement this, we reuse the existing daemonizing functions from the system emulator, which mainly do the following: - Fork off a child process, and set up a pipe between parent and child - The parent process waits until the child sends a status byte over the pipe (0 means that the child was set up successfully; anything else (including errors or EOF) means that the child was not set up successfully), and then exits with an appropriate exit status - The child process enters a new session (forking off again), changes the umask, and will ignore terminal signals from then on - Once set-up is complete, the child will chdir to /, redirect all standard I/O streams to /dev/null, and tell the parent that set-up has been completed successfully In contrast to qemu-nbd's --fork implementation, during the set up phase, error messages are not piped through the parent process. qemu-nbd mainly does this to detect errors, though (while os_daemonize() has the child explicitly signal success after set up); because we do not redirect stderr after forking, error messages continue to appear on whatever the parent's stderr was (until set up is complete). Signed-off-by: Hanna Reitz <hreitz@redhat.com> --- docs/tools/qemu-storage-daemon.rst | 7 +++++++ storage-daemon/qemu-storage-daemon.c | 15 +++++++++++++++ 2 files changed, 22 insertions(+)