I plan to add 'virsh event' to virsh-domain.c and 'virsh
net-event' to virsh-network.c; but as they will share quite
a bit of common boilerplate, it's better to set that up now
in virsh.c.
* tools/virsh.h (_vshControl): Add fields.
(vshEventStart, vshEventWait, vshEventDone, vshEventCleanup): New
prototypes.
* tools/virsh.c (vshEventFd, vshEventOldAction, vshEventInt)
(vshEventTimeout): New helper variables and functions.
(vshEventStart, vshEventWait, vshEventDone, vshEventCleanup):
Implement new functions.
(vshInit, vshDeinit, main): Manage event timeout.
Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
---
tools/virsh.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
tools/virsh.h | 13 +++++
2 files changed, 172 insertions(+), 1 deletion(-)
diff --git a/tools/virsh.c b/tools/virsh.c
index 944c037..2d4aaff 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -42,6 +42,7 @@
#include <sys/stat.h>
#include <inttypes.h>
#include <strings.h>
+#include <signal.h>
#include <libxml/parser.h>
#include <libxml/tree.h>
@@ -85,6 +86,11 @@
#include "virsh-snapshot.h"
#include "virsh-volume.h"
+/* Gnulib doesn't guarantee SA_SIGINFO support. */
+#ifndef SA_SIGINFO
+# define SA_SIGINFO 0
+#endif
+
static char *progname;
static const vshCmdGrp cmdGroups[];
@@ -2435,6 +2441,149 @@ vshEventLoop(void *opaque)
/*
+ * Helpers for waiting for a libvirt event.
+ */
+
+/* We want to use SIGINT to cancel a wait; but as signal handlers
+ * don't have an opaque argument, we have to use static storage. */
+static int vshEventFd = -1;
+static struct sigaction vshEventOldAction;
+
+
+/* Signal handler installed in vshEventStart, removed in vshEventCleanup. */
+static void
+vshEventInt(int sig ATTRIBUTE_UNUSED,
+ siginfo_t *siginfo ATTRIBUTE_UNUSED,
+ void *context ATTRIBUTE_UNUSED)
+{
+ char reason = VSH_EVENT_INTERRUPT;
+ if (vshEventFd >= 0)
+ ignore_value(safewrite(vshEventFd, &reason, 1));
+}
+
+
+/* Event loop handler used to limit length of waiting for any other event. */
+static void
+vshEventTimeout(int timer ATTRIBUTE_UNUSED,
+ void *opaque)
+{
+ vshControl *ctl = opaque;
+ char reason = VSH_EVENT_TIMEOUT;
+
+ if (ctl->eventPipe[1] >= 0)
+ ignore_value(safewrite(ctl->eventPipe[1], &reason, 1));
+}
+
+
+/**
+ * vshEventStart:
+ * @ctl virsh command struct
+ * @timeout_ms max wait time in milliseconds, or 0 for indefinite
+ *
+ * Set up a wait for a libvirt event. The wait can be canceled by
+ * SIGINT or by calling vshEventDone() in your event handler. If
+ * @timeout_ms is positive, the wait will also end if the timeout
+ * expires. Call vshEventWait() to block the main thread (the event
+ * handler runs in the event loop thread). When done (including if
+ * there was an error registering for an event), use vshEventCleanup()
+ * to quit waiting. Returns 0 on success, -1 on failure. */
+int
+vshEventStart(vshControl *ctl, int timeout_ms)
+{
+ struct sigaction action;
+
+ assert(ctl->eventPipe[0] == -1 && ctl->eventPipe[1] == -1 &&
+ vshEventFd == -1 && ctl->eventTimerId >= 0);
+ if (pipe2(ctl->eventPipe, O_CLOEXEC) < 0) {
+ char ebuf[1024];
+
+ vshError(ctl, _("failed to create pipe: %s"),
+ virStrerror(errno, ebuf, sizeof(ebuf)));
+ return -1;
+ }
+ vshEventFd = ctl->eventPipe[1];
+
+ action.sa_sigaction = vshEventInt;
+ action.sa_flags = SA_SIGINFO;
+ sigemptyset(&action.sa_mask);
+ sigaction(SIGINT, &action, &vshEventOldAction);
+
+ if (timeout_ms)
+ virEventUpdateTimeout(ctl->eventTimerId, timeout_ms);
+
+ return 0;
+}
+
+
+/**
+ * vshEventDone:
+ * @ctl virsh command struct
+ *
+ * Call this from an event callback to let the main thread quit
+ * blocking on further events.
+ */
+void
+vshEventDone(vshControl *ctl)
+{
+ char reason = VSH_EVENT_DONE;
+
+ if (ctl->eventPipe[1] >= 0)
+ ignore_value(safewrite(ctl->eventPipe[1], &reason, 1));
+}
+
+
+/**
+ * vshEventWait:
+ * @ctl virsh command struct
+ *
+ * Call this in the main thread after calling vshEventStart() then
+ * registering for one or more events. This call will block until
+ * SIGINT, the timeout registered at the start, or until one of your
+ * event handlers calls vshEventDone(). Returns an enum VSH_EVENT_*
+ * stating how the wait concluded, or -1 on error.
+ */
+int
+vshEventWait(vshControl *ctl)
+{
+ char buf;
+ int rv;
+
+ assert(ctl->eventPipe[0] >= 0);
+ while ((rv = read(ctl->eventPipe[0], &buf, 1)) < 0 && errno == EINTR);
+ if (rv != 1) {
+ char ebuf[1024];
+
+ if (!rv)
+ errno = EPIPE;
+ vshError(ctl, _("failed to determine loop exit status: %s"),
+ virStrerror(errno, ebuf, sizeof(ebuf)));
+ return -1;
+ }
+ return buf;
+}
+
+
+/**
+ * vshEventCleanup:
+ * @ctl virsh command struct
+ *
+ * Call at the end of any function that has used vshEventStart(), to
+ * tear down any remaining SIGINT or timeout handlers.
+ */
+void
+vshEventCleanup(vshControl *ctl)
+{
+ if (vshEventFd >= 0) {
+ sigaction(SIGINT, &vshEventOldAction, NULL);
+ vshEventFd = -1;
+ }
+ VIR_FORCE_CLOSE(ctl->eventPipe[0]);
+ VIR_FORCE_CLOSE(ctl->eventPipe[1]);
+ virEventUpdateTimeout(ctl->eventTimerId, -1);
+}
+
+
+/*
* Initialize debug settings.
*/
static void
@@ -2490,6 +2639,10 @@ vshInit(vshControl *ctl)
return false;
ctl->eventLoopStarted = true;
+ if ((ctl->eventTimerId = virEventAddTimeout(-1, vshEventTimeout, ctl,
+ NULL)) < 0)
+ return false;
+
if (ctl->name) {
vshReconnect(ctl);
/* Connecting to a named connection must succeed, but we delay
@@ -2933,6 +3086,9 @@ vshDeinit(vshControl *ctl)
if (timer != -1)
virEventRemoveTimeout(timer);
+ if (ctl->eventTimerId != -1)
+ virEventRemoveTimeout(ctl->eventTimerId);
+
ctl->eventLoopStarted = false;
}
@@ -3334,7 +3490,9 @@ main(int argc, char **argv)
ctl->log_fd = -1; /* Initialize log file descriptor */
ctl->debug = VSH_DEBUG_DEFAULT;
ctl->escapeChar = "^]"; /* Same default as telnet */
-
+ ctl->eventPipe[0] = -1;
+ ctl->eventPipe[1] = -1;
+ ctl->eventTimerId = -1;
if (!setlocale(LC_ALL, "")) {
perror("setlocale");
diff --git a/tools/virsh.h b/tools/virsh.h
index 4ee2d72..62a1eed 100644
--- a/tools/virsh.h
+++ b/tools/virsh.h
@@ -242,6 +242,9 @@ struct _vshControl {
virMutex lock;
bool eventLoopStarted;
bool quit;
+ int eventPipe[2]; /* Write-to-self pipe to end waiting for an
+ * event to occur */
+ int eventTimerId; /* id of event loop timeout registration */
const char *escapeChar; /* String representation of
console escape character */
@@ -369,6 +372,16 @@ int vshTTYRestore(vshControl *ctl);
int vshTTYMakeRaw(vshControl *ctl, bool report_errors);
bool vshTTYAvailable(vshControl *ctl);
+/* waiting for events */
+enum {
+ VSH_EVENT_INTERRUPT,
+ VSH_EVENT_TIMEOUT,
+ VSH_EVENT_DONE,
+};
+int vshEventStart(vshControl *ctl, int timeout_ms);
+void vshEventDone(vshControl *ctl);
+int vshEventWait(vshControl *ctl);
+void vshEventCleanup(vshControl *ctl);
/* allocation wrappers */
void *_vshMalloc(vshControl *ctl, size_t sz, const char *filename, int line);
--
1.8.5.3
--
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