89 lines
3.7 KiB
Diff
89 lines
3.7 KiB
Diff
From 2ec3ff668ff03410e94cfef8e3ee9384a8222211 Mon Sep 17 00:00:00 2001
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From: David Herrmann <dh.herrmann@gmail.com>
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Date: Fri, 19 Sep 2014 13:26:39 +0200
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Subject: [PATCH] login: pause devices before acknowledging VT switches
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If a session controller does not need synchronous VT switches, we allow
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them to pass VT control to logind, which acknowledges all VT switches
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unconditionally. This works fine with all sessions using the dbus API,
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but causes out-of-sync device use if we switch to legacy sessions that
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are notified via VT signals. Those are processed before logind notices
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the session-switch via sysfs. Therefore, leaving the old session still
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active for a short amount of time.
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This, in fact, may cause the legacy session to prepare graphics devices
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before the old session was deactivated, and thus, maybe causing the old
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session to interfer with graphics device usage.
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Fix this by releasing devices immediately before acknowledging VT
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switches. This way, sessions without VT handlers are required to support
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async session switching (which they do in that case, anyway).
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---
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src/login/logind-session.c | 21 +++++++++++++++++++++
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src/login/logind-session.h | 1 +
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src/login/logind.c | 4 ++--
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3 files changed, 24 insertions(+), 2 deletions(-)
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diff --git a/src/login/logind-session.c b/src/login/logind-session.c
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index eeb58c9031..477ac9ab1b 100644
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--- a/src/login/logind-session.c
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+++ b/src/login/logind-session.c
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@@ -1053,6 +1053,27 @@ void session_restore_vt(Session *s) {
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s->vtfd = safe_close(s->vtfd);
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}
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+void session_leave_vt(Session *s) {
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+ assert(s);
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+
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+ /* This is called whenever we get a VT-switch signal from the kernel.
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+ * We acknowledge all of them unconditionally. Note that session are
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+ * free to overwrite those handlers and we only register them for
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+ * sessions with controllers. Legacy sessions are not affected.
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+ * However, if we switch from a non-legacy to a legacy session, we must
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+ * make sure to pause all device before acknowledging the switch. We
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+ * process the real switch only after we are notified via sysfs, so the
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+ * legacy session might have already started using the devices. If we
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+ * don't pause the devices before the switch, we might confuse the
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+ * session we switch to. */
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+
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+ if (s->vtfd < 0)
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+ return;
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+
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+ session_device_pause_all(s);
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+ ioctl(s->vtfd, VT_RELDISP, 1);
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+}
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+
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bool session_is_controller(Session *s, const char *sender) {
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assert(s);
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diff --git a/src/login/logind-session.h b/src/login/logind-session.h
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index 9fb0188a84..a007fb5e84 100644
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--- a/src/login/logind-session.h
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+++ b/src/login/logind-session.h
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@@ -174,6 +174,7 @@ KillWho kill_who_from_string(const char *s) _pure_;
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int session_prepare_vt(Session *s);
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void session_restore_vt(Session *s);
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+void session_leave_vt(Session *s);
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bool session_is_controller(Session *s, const char *sender);
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int session_set_controller(Session *s, const char *sender, bool force);
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diff --git a/src/login/logind.c b/src/login/logind.c
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index f1b6a86298..8f00c46339 100644
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--- a/src/login/logind.c
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+++ b/src/login/logind.c
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@@ -750,11 +750,11 @@ static int manager_vt_switch(sd_event_source *src, const struct signalfd_siginfo
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}
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if (active->vtfd >= 0) {
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- ioctl(active->vtfd, VT_RELDISP, 1);
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+ session_leave_vt(active);
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} else {
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LIST_FOREACH(sessions_by_seat, iter, m->seat0->sessions) {
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if (iter->vtnr == active->vtnr && iter->vtfd >= 0) {
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- ioctl(iter->vtfd, VT_RELDISP, 1);
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+ session_leave_vt(iter);
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break;
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}
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}
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