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Avoid polling on FDs with no events enabled

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If a file descriptor with events=0 was added to the libvirtd
event loop, it would still be added to the poll() fds' array.
While it wouldn't see any POLLIN/OUT events, it'd still get
triggered for HANGUP/ERROR events which was not in compliance
with the libvirt events API contract.

* qemud/event.c: Don't poll on FDs with events=0
* tests/eventtest.c: Add test case to validate fix to event.c
This commit is contained in:
Daniel P. Berrange 2009-08-24 17:27:55 +01:00
parent 77a1f418c8
commit 34d22c1ed5
2 changed files with 57 additions and 16 deletions
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54
qemud/event.c
View File

@ -109,7 +109,7 @@ int virEventAddHandleImpl(int fd, int events,
void *opaque,
virFreeCallback ff) {
int watch;
EVENT_DEBUG("Add handle %d %d %p %p", fd, events, cb, opaque);
EVENT_DEBUG("Add handle fd=%d events=%d cb=%p opaque=%p", fd, events, cb, opaque);
virEventLock();
if (eventLoop.handlesCount == eventLoop.handlesAlloc) {
EVENT_DEBUG("Used %d handle slots, adding %d more",
@ -170,7 +170,7 @@ void virEventUpdateHandleImpl(int watch, int events) {
*/
int virEventRemoveHandleImpl(int watch) {
int i;
EVENT_DEBUG("Remove handle %d", watch);
EVENT_DEBUG("Remove handle w=%d", watch);
if (watch <= 0) {
VIR_WARN("Ignoring invalid remove watch %d", watch);
@ -350,22 +350,32 @@ static int virEventCalculateTimeout(int *timeout) {
* file handles. The caller must free the returned data struct
* returns: the pollfd array, or NULL on error
*/
static struct pollfd *virEventMakePollFDs(void) {
static struct pollfd *virEventMakePollFDs(int *nfds) {
struct pollfd *fds;
int i;
*nfds = 0;
for (i = 0 ; i < eventLoop.handlesCount ; i++) {
if (eventLoop.handles[i].events)
(*nfds)++;
}
/* Setup the poll file handle data structs */
if (VIR_ALLOC_N(fds, eventLoop.handlesCount) < 0)
if (VIR_ALLOC_N(fds, *nfds) < 0)
return NULL;
*nfds = 0;
for (i = 0 ; i < eventLoop.handlesCount ; i++) {
EVENT_DEBUG("Prepare n=%d w=%d, f=%d e=%d", i,
eventLoop.handles[i].watch,
eventLoop.handles[i].fd,
eventLoop.handles[i].events);
fds[i].fd = eventLoop.handles[i].fd;
fds[i].events = eventLoop.handles[i].events;
fds[i].revents = 0;
if (!eventLoop.handles[i].events)
continue;
fds[*nfds].fd = eventLoop.handles[i].fd;
fds[*nfds].events = eventLoop.handles[i].events;
fds[*nfds].revents = 0;
(*nfds)++;
//EVENT_DEBUG("Wait for %d %d", eventLoop.handles[i].fd, eventLoop.handles[i].events);
}
@ -391,6 +401,7 @@ static int virEventDispatchTimeouts(void) {
int i;
/* Save this now - it may be changed during dispatch */
int ntimeouts = eventLoop.timeoutsCount;
DEBUG("Dispatch %d", ntimeouts);
if (gettimeofday(&tv, NULL) < 0) {
return -1;
@ -429,28 +440,38 @@ static int virEventDispatchTimeouts(void) {
* Returns 0 upon success, -1 if an error occurred
*/
static int virEventDispatchHandles(int nfds, struct pollfd *fds) {
int i;
int i, n;
DEBUG("Dispatch %d", nfds);
/* NB, use nfds not eventLoop.handlesCount, because new
* fds might be added on end of list, and they're not
* in the fds array we've got */
for (i = 0 ; i < nfds ; i++) {
for (i = 0, n = 0 ; n < nfds && i < eventLoop.handlesCount ; n++) {
while ((eventLoop.handles[i].fd != fds[n].fd ||
eventLoop.handles[i].events == 0) &&
i < eventLoop.handlesCount) {
i++;
}
if (i == eventLoop.handlesCount)
break;
DEBUG("i=%d w=%d", i, eventLoop.handles[i].watch);
if (eventLoop.handles[i].deleted) {
EVENT_DEBUG("Skip deleted n=%d w=%d f=%d", i,
eventLoop.handles[i].watch, eventLoop.handles[i].fd);
continue;
}
if (fds[i].revents) {
if (fds[n].revents) {
virEventHandleCallback cb = eventLoop.handles[i].cb;
void *opaque = eventLoop.handles[i].opaque;
int hEvents = virPollEventToEventHandleType(fds[i].revents);
int hEvents = virPollEventToEventHandleType(fds[n].revents);
EVENT_DEBUG("Dispatch n=%d f=%d w=%d e=%d %p", i,
fds[i].fd, eventLoop.handles[i].watch,
fds[i].revents, eventLoop.handles[i].opaque);
fds[n].fd, eventLoop.handles[i].watch,
fds[n].revents, eventLoop.handles[i].opaque);
virEventUnlock();
(cb)(eventLoop.handles[i].watch,
fds[i].fd, hEvents, opaque);
fds[n].fd, hEvents, opaque);
virEventLock();
}
}
@ -465,6 +486,7 @@ static int virEventDispatchHandles(int nfds, struct pollfd *fds) {
*/
static int virEventCleanupTimeouts(void) {
int i;
DEBUG("Cleanup %d", eventLoop.timeoutsCount);
/* Remove deleted entries, shuffling down remaining
* entries as needed to form contiguous series
@ -505,6 +527,7 @@ static int virEventCleanupTimeouts(void) {
*/
static int virEventCleanupHandles(void) {
int i;
DEBUG("Cleanupo %d", eventLoop.handlesCount);
/* Remove deleted entries, shuffling down remaining
* entries as needed to form contiguous series
@ -554,10 +577,9 @@ int virEventRunOnce(void) {
virEventCleanupHandles() < 0)
goto error;
if (!(fds = virEventMakePollFDs()) ||
if (!(fds = virEventMakePollFDs(&nfds)) ||
virEventCalculateTimeout(&timeout) < 0)
goto error;
nfds = eventLoop.handlesCount;
virEventUnlock();

19
tests/eventtest.c
View File

@ -430,6 +430,25 @@ mymain(int argc, char **argv)
for (i = 0 ; i < NUM_TIME ; i++)
virEventRemoveTimeoutImpl(timers[i].timer);
resetAll();
/* Final test, register same FD twice, once with no
* events, and make sure the right callback runs */
handles[0].pipeFD[0] = handles[1].pipeFD[0];
handles[0].pipeFD[1] = handles[1].pipeFD[1];
handles[0].watch = virEventAddHandleImpl(handles[0].pipeFD[0],
0,
testPipeReader,
&handles[0], NULL);
handles[1].watch = virEventAddHandleImpl(handles[1].pipeFD[0],
VIR_EVENT_HANDLE_READABLE,
testPipeReader,
&handles[1], NULL);
startJob("Write duplicate", &test);
ret = safewrite(handles[1].pipeFD[1], &one, 1);
if (finishJob(1, -1) != EXIT_SUCCESS)
return EXIT_FAILURE;
//pthread_kill(eventThread, SIGTERM);