[PATCH] os: Add -displayfd option
Chase Douglas
chase.douglas at canonical.com
Tue Apr 3 11:34:34 PDT 2012
This option specifies a file descriptor in the launching process. X
will scan for an available display number and write that number back to
the launching process, at the same time as SIGUSR1 generation. This
means display managers don't need to guess at available display numbers.
As a consequence, if X fails to start when using -displayfd, it's not
because the display was in use, so there's no point in retrying the X
launch on a higher display number.
Signed-off-by: Adam Jackson <ajax at redhat.com>
Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
---
Adam originally submitted this back in 2007
(http://patchwork.freedesktop.org/patch/3574/). I think this will be helpful for
starting X servers for test suites, among other uses. I am resurrecting this
with the following changes:
* Reformatted to match master
* Closed displayfd after writing display name (from previous review)
* In TryCreateSocket(), return Bool value appropriately (from previous review)
* In CreateWellKnownSockets(), use X_TCP_PORT as offset (from previous review)
* Write to displayfd before signaling to parent
Unfortunately, I'm not in a position to test this right now. I'm in the middle
of fixing bugs for the impending Ubuntu release. I know that it does compile,
cleanly I think (there are lots of other irrelevant warnings, though). If
someone could give this a whirl to see that it functions properly I would
appreciate it.
dix/globals.c | 1 +
include/opaque.h | 1 +
man/Xserver.man | 7 +++++
os/connection.c | 65 +++++++++++++++++++++++++++++++++++++----------------
os/utils.c | 9 +++++++
5 files changed, 63 insertions(+), 20 deletions(-)
diff --git a/dix/globals.c b/dix/globals.c
index a564575..332b91f 100644
--- a/dix/globals.c
+++ b/dix/globals.c
@@ -128,6 +128,7 @@ int defaultColorVisualClass = -1;
int monitorResolution = 0;
char *display;
+int displayfd;
char *ConnectionInfo;
CARD32 TimeOutValue = DEFAULT_TIMEOUT * MILLI_PER_SECOND;
diff --git a/include/opaque.h b/include/opaque.h
index 9ca408a..b76ab6e 100644
--- a/include/opaque.h
+++ b/include/opaque.h
@@ -50,6 +50,7 @@ extern _X_EXPORT int ScreenSaverAllowExposures;
extern _X_EXPORT int defaultScreenSaverBlanking;
extern _X_EXPORT int defaultScreenSaverAllowExposures;
extern _X_EXPORT char *display;
+extern _X_EXPORT int displayfd;
extern _X_EXPORT int defaultBackingStore;
extern _X_EXPORT Bool disableBackingStore;
diff --git a/man/Xserver.man b/man/Xserver.man
index 0cd9b94..8d243d6 100644
--- a/man/Xserver.man
+++ b/man/Xserver.man
@@ -127,6 +127,13 @@ Not obeyed by all servers.
.B \-core
causes the server to generate a core dump on fatal errors.
.TP 8
+.B \-displayfd \fIfd\fP
+specifies a file descriptor in the launching process. Rather than specify
+a display number, the X server will attempt to listen on successively higher
+display numbers, and upon finding a free one, will write the port number back
+on this file descriptor as a newline-terminated string. The \-pn option is
+ignored when using \-displayfd.
+.TP 8
.B \-deferglyphs \fIwhichfonts\fP
specifies the types of fonts for which the server should attempt to use
deferred glyph loading. \fIwhichfonts\fP can be all (all fonts),
diff --git a/os/connection.c b/os/connection.c
index 1099752..94e565d 100644
--- a/os/connection.c
+++ b/os/connection.c
@@ -142,6 +142,7 @@ Bool AnyClientsWriteBlocked; /* true if some client blocked on write */
static Bool RunFromSmartParent; /* send SIGUSR1 to parent process */
Bool RunFromSigStopParent; /* send SIGSTOP to our own process; Upstart (or
equivalent) will send SIGCONT back. */
+static char dynamic_display[7]; /* display name */
Bool PartialNetwork; /* continue even if unable to bind all addrs */
static Pid_t ParentProcess;
@@ -350,6 +351,10 @@ void
NotifyParentProcess(void)
{
#if !defined(WIN32)
+ if (dynamic_display[0]) {
+ write(displayfd, dynamic_display, strlen(dynamic_display));
+ close(displayfd);
+ }
if (RunFromSmartParent) {
if (ParentProcess > 1) {
kill(ParentProcess, SIGUSR1);
@@ -360,6 +365,18 @@ NotifyParentProcess(void)
#endif
}
+static Bool
+TryCreateSocket(int num, int *partial)
+{
+ char port[20];
+
+ sprintf(port, "%d", num);
+
+ return (_XSERVTransMakeAllCOTSServerListeners(port, partial,
+ &ListenTransCount,
+ &ListenTransConns) >= 0);
+}
+
/*****************
* CreateWellKnownSockets
* At initialization, create the sockets to listen on for new clients.
@@ -370,7 +387,6 @@ CreateWellKnownSockets(void)
{
int i;
int partial;
- char port[20];
FD_ZERO(&AllSockets);
FD_ZERO(&AllClients);
@@ -386,29 +402,38 @@ CreateWellKnownSockets(void)
FD_ZERO(&WellKnownConnections);
- snprintf(port, sizeof(port), "%d", atoi(display));
-
- if ((_XSERVTransMakeAllCOTSServerListeners(port, &partial,
- &ListenTransCount,
- &ListenTransConns) >= 0) &&
- (ListenTransCount >= 1)) {
- if (!PartialNetwork && partial) {
- FatalError("Failed to establish all listening sockets");
+ if (display) {
+ if (TryCreateSocket(atoi(display), &partial) &&
+ ListenTransCount >= 1)
+ if (!PartialNetwork && partial)
+ FatalError ("Failed to establish all listening sockets");
+ }
+ else { /* -displayfd */
+ Bool found = 0;
+ for (i = 0; i < 65535 - X_TCP_PORT; i++) {
+ if (!TryCreateSocket(i, &partial) && !partial) {
+ found = 1;
+ break;
+ }
+ else
+ CloseWellKnownConnections();
}
- else {
- ListenTransFds = malloc(ListenTransCount * sizeof(int));
+ if (!found)
+ FatalError("Failed to find a socket to listen on");
+ sprintf(dynamic_display, "%d\n", i);
+ display = dynamic_display;
+ }
- for (i = 0; i < ListenTransCount; i++) {
- int fd = _XSERVTransGetConnectionNumber(ListenTransConns[i]);
+ ListenTransFds = malloc(ListenTransCount * sizeof (int));
- ListenTransFds[i] = fd;
- FD_SET(fd, &WellKnownConnections);
+ for (i = 0; i < ListenTransCount; i++) {
+ int fd = _XSERVTransGetConnectionNumber(ListenTransConns[i]);
- if (!_XSERVTransIsLocal(ListenTransConns[i])) {
- DefineSelf(fd);
- }
- }
- }
+ ListenTransFds[i] = fd;
+ FD_SET(fd, &WellKnownConnections);
+
+ if (!_XSERVTransIsLocal(ListenTransConns[i]))
+ DefineSelf (fd);
}
if (!XFD_ANYSET(&WellKnownConnections))
diff --git a/os/utils.c b/os/utils.c
index 30592d2..3a1ef93 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -659,6 +659,15 @@ ProcessCommandLine(int argc, char *argv[])
else
UseMsg();
}
+ else if (strcmp(argv[i], "-displayfd") == 0) {
+ if (++i < argc) {
+ displayfd = atoi(argv[i]);
+ display = NULL;
+ nolock = TRUE;
+ }
+ else
+ UseMsg();
+ }
#ifdef DPMSExtension
else if (strcmp(argv[i], "dpms") == 0)
/* ignored for compatibility */ ;
--
1.7.9.1
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