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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 22/27] libxl: provide progress reporting for long-running operations
This will be used for reporting, during domain creation, that the
console is ready.
Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Changes since v7:
* If aop->how.callback, actually add the aop to the for_callback list (!)
* Document the threadsafety of aop's, and make appropriate cross-references.
* Allocate the actual aop from its thread's egc; do not free it.
* Remove pointless code motion of libxl__ao_create.
* Minor formatting fixes.
---
tools/libxl/libxl.h | 45 ++++++++++++++++++++++++++
tools/libxl/libxl_event.c | 72 ++++++++++++++++++++++++++++++++++++++++--
tools/libxl/libxl_internal.h | 35 ++++++++++++++++++++
3 files changed, 149 insertions(+), 3 deletions(-)
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index e19d947..ba0f4de 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -435,6 +435,51 @@ typedef struct {
} u;
} libxl_asyncop_how;
+/*
+ * Some more complex asynchronous operations can report intermediate
+ * progress. How this is to be reported is controlled, for each
+ * function, by a parameter
+ * libxl_asyncprogress_how *aop_FOO_how;
+ * for each kind of progress FOO supported by that function. Each
+ * such kind of progress is associated with an event type.
+ *
+ * The function description will document whether, when, and how
+ * many times, the intermediate progress will be reported, and
+ * what the corresponding event type(s) are.
+ *
+ * If aop_FOO_how==NULL, intermediate progress reports are discarded.
+ *
+ * If aop_FOO_how->callback==NULL, intermediate progress reports
+ * generate libxl events which can be obtained from libxl_event_wait
+ * or libxl_event_check.
+ *
+ * If aop_FOO_how->callback!=NULL, libxl will report intermediate
+ * progress by calling callback(ctx, &event, for_callback).
+ *
+ * The rules for these events are otherwise the same as those for
+ * ordinary events. The reentrancy and threading rules for the
+ * callback are the same as those for ao completion callbacks.
+ *
+ * Note that the callback, if provided, is responsible for freeing
+ * the event.
+ *
+ * If callbacks are requested, they will be made, and returned, before
+ * the long-running libxl operation is considered finished (so if the
+ * long-running libxl operation was invoked with ao_how==NULL then any
+ * callbacks will occur strictly before the long-running operation
+ * returns). However, the callbacks may occur on any thread.
+ *
+ * In general, otherwise, no promises are made about the relative
+ * order of callbacks in a multithreaded program. In particular
+ * different callbacks relating to the same long-running operation may
+ * be delivered out of order.
+ */
+
+typedef struct {
+ void (*callback)(libxl_ctx *ctx, libxl_event*, void *for_callback);
+ libxl_ev_user for_event; /* always used */
+ void *for_callback; /* passed to callback */
+} libxl_asyncprogress_how;
#define LIBXL_VERSION 0
diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index b546471..460ef66 100644
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -902,18 +902,29 @@ void libxl__event_disaster(libxl__egc *egc, const char
*msg, int errnoval,
static void egc_run_callbacks(libxl__egc *egc)
{
/*
- * The callbacks must happen with the ctx unlocked.
- * See the comment near #define EGC_GC in libxl_internal.h and
- * those in the definitions of libxl__egc and libxl__ao.
+ * The callbacks must happen with the ctx unlocked. See the
+ * comment near #define EGC_GC in libxl_internal.h and those in
+ * the definitions of libxl__egc, libxl__ao and libxl__aop.
*/
EGC_GC;
libxl_event *ev, *ev_tmp;
+ libxl__aop_occurred *aop, *aop_tmp;
LIBXL_TAILQ_FOREACH_SAFE(ev, &egc->occurred_for_callback, link, ev_tmp) {
LIBXL_TAILQ_REMOVE(&egc->occurred_for_callback, ev, link);
CTX->event_hooks->event_occurs(CTX->event_hooks_user, ev);
}
+ LIBXL_TAILQ_FOREACH_SAFE(aop, &egc->aops_for_callback, entry, aop_tmp) {
+ LIBXL_TAILQ_REMOVE(&egc->aops_for_callback, aop, entry);
+ aop->how->callback(CTX, aop->ev, aop->how->for_callback);
+
+ CTX_LOCK;
+ aop->ao->progress_reports_outstanding--;
+ libxl__ao_complete_check_progress_reports(egc, aop->ao);
+ CTX_UNLOCK;
+ }
+
libxl__ao *ao, *ao_tmp;
LIBXL_TAILQ_FOREACH_SAFE(ao, &egc->aos_for_callback,
entry_for_callback, ao_tmp) {
@@ -1296,6 +1307,7 @@ void libxl__ao_abort(libxl__ao *ao)
assert(ao->magic == LIBXL__AO_MAGIC);
assert(ao->in_initiator);
assert(!ao->complete);
+ assert(!ao->progress_reports_outstanding);
libxl__ao__destroy(CTX, ao);
}
@@ -1306,6 +1318,24 @@ void libxl__ao_complete(libxl__egc *egc, libxl__ao *ao,
int rc)
ao->complete = 1;
ao->rc = rc;
+ libxl__ao_complete_check_progress_reports(egc, ao);
+}
+
+void libxl__ao_complete_check_progress_reports(libxl__egc *egc, libxl__ao *ao)
+{
+ /*
+ * We don't consider an ao complete if it has any outstanding
+ * callbacks. These callbacks might be outstanding on other
+ * threads, queued up in the other threads' egc's. Those threads
+ * will, after making the callback, take out the lock again,
+ * decrement progress_reports_outstanding, and call us again.
+ */
+
+ assert(ao->progress_reports_outstanding >= 0);
+
+ if (!ao->complete || ao->progress_reports_outstanding)
+ return;
+
if (ao->poller) {
assert(ao->in_initiator);
if (!ao->constructing)
@@ -1355,6 +1385,7 @@ libxl__ao *libxl__ao_create(libxl_ctx *ctx, uint32_t
domid,
return NULL;
}
+
int libxl__ao_inprogress(libxl__ao *ao)
{
AO_GC;
@@ -1412,6 +1443,41 @@ int libxl__ao_inprogress(libxl__ao *ao)
}
+/* progress reporting */
+
+/* The application indicates a desire to ignore events by passing NULL
+ * for how. But we want to copy *how. So we have this dummy function
+ * whose address is stored in callback if the app passed how==NULL. */
+static void dummy_asyncprogress_callback_ignore
+ (libxl_ctx *ctx, libxl_event *ev, void *for_callback) { }
+
+void libxl__ao_progress_gethow(libxl_asyncprogress_how *in_state,
+ const libxl_asyncprogress_how *from_app) {
+ if (from_app)
+ *in_state = *from_app;
+ else
+ in_state->callback = dummy_asyncprogress_callback_ignore;
+}
+
+void libxl__ao_progress_report(libxl__egc *egc, libxl__ao *ao,
+ const libxl_asyncprogress_how *how, libxl_event *ev)
+{
+ ev->for_user = how->for_event;
+ if (how->callback == dummy_asyncprogress_callback_ignore) {
+ /* ignore */
+ } else if (how->callback) {
+ libxl__aop_occurred *aop = libxl__zalloc(&egc->gc, sizeof(*aop));
+ ao->progress_reports_outstanding++;
+ aop->ao = ao;
+ aop->ev = ev;
+ aop->how = how;
+ LIBXL_TAILQ_INSERT_TAIL(&egc->aops_for_callback, aop, entry);
+ } else {
+ libxl__event_occurred(egc, ev);
+ }
+}
+
+
/*
* Local variables:
* mode: C
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index f48cfdc..d5cf69a 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -119,6 +119,7 @@ _hidden void libxl__log(libxl_ctx *ctx, xentoollog_level
msglevel, int errnoval,
typedef struct libxl__gc libxl__gc;
typedef struct libxl__egc libxl__egc;
typedef struct libxl__ao libxl__ao;
+typedef struct libxl__aop_occurred libxl__aop_occurred;
_hidden void libxl__alloc_failed(libxl_ctx *, const char *func,
size_t nmemb, size_t size) __attribute__((noreturn));
@@ -364,6 +365,21 @@ struct libxl__egc {
struct libxl__gc gc;
struct libxl__event_list occurred_for_callback;
LIBXL_TAILQ_HEAD(, libxl__ao) aos_for_callback;
+ LIBXL_TAILQ_HEAD(, libxl__aop_occurred) aops_for_callback;
+};
+
+struct libxl__aop_occurred {
+ /*
+ * An aop belongs to, and may be accessed only on, the thread
+ * which created it. It normally lives in that thread's egc.
+ *
+ * While an aop exists, it corresponds to one refcount in
+ * ao->progress_reports_outstanding, preventing ao destruction.
+ */
+ LIBXL_TAILQ_ENTRY(libxl__aop_occurred) entry;
+ libxl__ao *ao;
+ libxl_event *ev;
+ const libxl_asyncprogress_how *how;
};
#define LIBXL__AO_MAGIC 0xA0FACE00ul
@@ -386,6 +402,7 @@ struct libxl__ao {
*/
uint32_t magic;
unsigned constructing:1, in_initiator:1, complete:1, notified:1;
+ int progress_reports_outstanding;
int rc;
libxl__gc gc;
libxl_asyncop_how how;
@@ -1402,6 +1419,7 @@ libxl__device_model_version_running(libxl__gc *gc,
uint32_t domid);
LIBXL_INIT_GC((egc).gc,ctx); \
LIBXL_TAILQ_INIT(&(egc).occurred_for_callback); \
LIBXL_TAILQ_INIT(&(egc).aos_for_callback); \
+ LIBXL_TAILQ_INIT(&(egc).aops_for_callback); \
} while(0)
_hidden void libxl__egc_cleanup(libxl__egc *egc);
@@ -1448,6 +1466,9 @@ _hidden void libxl__egc_cleanup(libxl__egc *egc);
* pointer to the internal event generation request routines
* libxl__evgen_FOO, so that at some point a CALLBACK will be
* made when the operation is complete.
+ * - if the operation provides progress reports, the aop_how(s)
+ * must be copied into the per-operation structure using
+ * libxl__ao_progress_gethow.
*
* - If initiation is successful, the initiating function needs
* to run libxl__ao_inprogress right before unlocking and
@@ -1457,6 +1478,10 @@ _hidden void libxl__egc_cleanup(libxl__egc *egc);
* call libxl__ao_abort before unlocking and returning whatever
* error code is appropriate (AO_ABORT macro).
*
+ * - If the operation supports progress reports, it may generate
+ * suitable events with NEW_EVENT and report them with
+ * libxl__ao_progress_report (with the ctx locked).
+ *
* - Later, some callback function, whose callback has been requested
* directly or indirectly, should call libxl__ao_complete (with the
* ctx locked, as it will generally already be in any event callback
@@ -1512,8 +1537,18 @@ _hidden int libxl__ao_inprogress(libxl__ao *ao); /*
temporarily unlocks */
_hidden void libxl__ao_abort(libxl__ao *ao);
_hidden void libxl__ao_complete(libxl__egc *egc, libxl__ao *ao, int rc);
+/* Can be called at any time. Use is essential for any aop user. */
+_hidden void libxl__ao_progress_gethow(libxl_asyncprogress_how *in_state,
+ const libxl_asyncprogress_how
*from_app);
+
+/* Must be called with the ctx locked. Will fill in ev->for_user,
+ * so caller need not do that. */
+_hidden void libxl__ao_progress_report(libxl__egc *egc, libxl__ao *ao,
+ const libxl_asyncprogress_how *how, libxl_event *ev /* consumed */);
+
/* For use by ao machinery ONLY */
_hidden void libxl__ao__destroy(libxl_ctx*, libxl__ao *ao);
+_hidden void libxl__ao_complete_check_progress_reports(libxl__egc*,
libxl__ao*);
/*
--
1.7.2.5
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