[systemd-devel] [PATCH] login: share VT-signal handler between sessions
Olivier Brunel
jjk at jjacky.com
Mon Aug 11 10:57:15 PDT 2014
On 08/11/14 18:21, David Herrmann wrote:
> sd-event does not allow multiple handlers for a single signal. However,
> logind sets up signal handlers for each session with VT_PROCESS set (that
> is, it has an active controller). Therefore, registering multiple such
> controllers will fail.
>
> Lets make the VT-handler global, as it's mostly trivial, anyway. This way,
> the sessions don't have to take care of that and we can simply acknowledge
> all VT-switch requests as we always did.
> ---
> Hi Olivier
>
> Can you give this a try? It should solve your issues.
Yes, just tried it -- it does solve the issue.
Thanks guys,
-j
BTW there's a bug report opened about this issue:
https://bugs.freedesktop.org/show_bug.cgi?id=81932
>
> Thanks
> David
>
> src/login/logind-session.c | 26 ++-----------------
> src/login/logind-session.h | 1 -
> src/login/logind.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 64 insertions(+), 25 deletions(-)
>
> diff --git a/src/login/logind-session.c b/src/login/logind-session.c
> index fdeacb1..26b6a90 100644
> --- a/src/login/logind-session.c
> +++ b/src/login/logind-session.c
> @@ -153,8 +153,6 @@ void session_free(Session *s) {
>
> hashmap_remove(s->manager->sessions, s->id);
>
> - s->vt_source = sd_event_source_unref(s->vt_source);
> -
> free(s->state_file);
> free(s);
> }
> @@ -994,19 +992,9 @@ static int session_open_vt(Session *s) {
> return s->vtfd;
> }
>
> -static int session_vt_fn(sd_event_source *source, const struct signalfd_siginfo *si, void *data) {
> - Session *s = data;
> -
> - if (s->vtfd >= 0)
> - ioctl(s->vtfd, VT_RELDISP, 1);
> -
> - return 0;
> -}
> -
> void session_prepare_vt(Session *s) {
> int vt, r;
> struct vt_mode mode = { 0 };
> - sigset_t mask;
>
> vt = session_open_vt(s);
> if (vt < 0)
> @@ -1024,20 +1012,12 @@ void session_prepare_vt(Session *s) {
> if (r < 0)
> goto error;
>
> - sigemptyset(&mask);
> - sigaddset(&mask, SIGUSR1);
> - sigprocmask(SIG_BLOCK, &mask, NULL);
> -
> - r = sd_event_add_signal(s->manager->event, &s->vt_source, SIGUSR1, session_vt_fn, s);
> - if (r < 0)
> - goto error;
> -
> /* Oh, thanks to the VT layer, VT_AUTO does not work with KD_GRAPHICS.
> * So we need a dummy handler here which just acknowledges *all* VT
> * switch requests. */
> mode.mode = VT_PROCESS;
> - mode.relsig = SIGUSR1;
> - mode.acqsig = SIGUSR1;
> + mode.relsig = SIGRTMIN;
> + mode.acqsig = SIGRTMIN + 1;
> r = ioctl(vt, VT_SETMODE, &mode);
> if (r < 0)
> goto error;
> @@ -1058,8 +1038,6 @@ void session_restore_vt(Session *s) {
> if (vt < 0)
> return;
>
> - s->vt_source = sd_event_source_unref(s->vt_source);
> -
> ioctl(vt, KDSETMODE, KD_TEXT);
>
> if (read_one_line_file("/sys/module/vt/parameters/default_utf8", &utf8) >= 0 && *utf8 == '1')
> diff --git a/src/login/logind-session.h b/src/login/logind-session.h
> index e62b76d..562332c 100644
> --- a/src/login/logind-session.h
> +++ b/src/login/logind-session.h
> @@ -98,7 +98,6 @@ struct Session {
> Seat *seat;
> unsigned int vtnr;
> int vtfd;
> - sd_event_source *vt_source;
>
> pid_t leader;
> uint32_t audit_id;
> diff --git a/src/login/logind.c b/src/login/logind.c
> index ec5529d..b470916 100644
> --- a/src/login/logind.c
> +++ b/src/login/logind.c
> @@ -720,6 +720,46 @@ static int manager_connect_bus(Manager *m) {
> return 0;
> }
>
> +static int manager_vt_switch(sd_event_source *src, const struct signalfd_siginfo *si, void *data) {
> + Manager *m = data;
> + Session *active, *iter;
> +
> + /*
> + * We got a VT-switch signal and we have to acknowledge it immediately.
> + * Preferably, we'd just use m->seat0->active->vtfd, but unfortunately,
> + * old user-space might run multiple sessions on a single VT, *sigh*.
> + * Therefore, we have to iterate all sessions and find one with a vtfd
> + * on the requested VT.
> + * As only VTs with active controllers have VT_PROCESS set, our current
> + * notion of the active VT might be wrong (for instance if the switch
> + * happens while we setup VT_PROCESS). Therefore, read the current VT
> + * first and then use s->active->vtnr as reference. Note that this is
> + * not racy, as no further VT-switch can happen as long as we're in
> + * synchronous VT_PROCESS mode.
> + */
> +
> + seat_read_active_vt(m->seat0);
> +
> + active = m->seat0->active;
> + if (!active || active->vtnr < 1) {
> + log_warning("Received VT_PROCESS signal without a registered session on that VT.");
> + return 0;
> + }
> +
> + if (active->vtfd >= 0) {
> + ioctl(active->vtfd, VT_RELDISP, 1);
> + } else {
> + LIST_FOREACH(sessions_by_seat, iter, m->seat0->sessions) {
> + if (iter->vtnr == active->vtnr && iter->vtfd >= 0) {
> + ioctl(iter->vtfd, VT_RELDISP, 1);
> + break;
> + }
> + }
> + }
> +
> + return 0;
> +}
> +
> static int manager_connect_console(Manager *m) {
> int r;
>
> @@ -750,6 +790,28 @@ static int manager_connect_console(Manager *m) {
> return r;
> }
>
> + /*
> + * SIGRTMIN is used as global VT-release signal, SIGRTMIN + 1 is used
> + * as VT-acquire signal. We ignore any acquire-events (yes, we still
> + * have to provide a valid signal-number for it!) and acknowledge all
> + * release events immediately.
> + */
> +
> + if (SIGRTMIN + 1 > SIGRTMAX) {
> + log_error("Not enough real-time signals available: %u-%u", SIGRTMIN, SIGRTMAX);
> + return -EINVAL;
> + }
> +
> + r = sigprocmask_many(SIG_BLOCK, SIGRTMIN, SIGRTMIN + 1, -1);
> + if (r < 0) {
> + log_error("Cannot block SIGRTMIN and SIGRTMIN + 1: %s", strerror(-r));
> + return r;
> + }
> +
> + r = sd_event_add_signal(m->event, NULL, SIGRTMIN, manager_vt_switch, m);
> + if (r < 0)
> + return r;
> +
> return 0;
> }
>
>
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