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librados: fix async aio completion wakeup

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For aio flush, we register a wait on the most recent write.  The write
completion code, however, was *only* waking the waiter if they were waiting
on that write, without regard to previous writes (completed or not).
For example, we might have 6 and 7 outstanding and wait on 7.  If they
finish in order all is well, but if 7 finishes first we do the flush
completion early.  Similarly, if we

 - start 6
 - start 7
 - finish 7
 - flush; wait on 7
 - finish 6

we can hang forever.

Fix by doing any completions that are prior to the oldest pending write in
the aio write completion handler.

Refs: #5919

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
Tested-by: Oliver Francke <Oliver.Francke@filoo.de>
This commit is contained in:
Sage Weil 2013-08-13 12:52:41 -07:00
parent 7a52e2ff50
commit 16ed0b9af8
1 changed files with 17 additions and 12 deletions
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29
src/librados/IoCtxImpl.cc
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@ -82,22 +82,25 @@ void librados::IoCtxImpl::complete_aio_write(AioCompletionImpl *c)
aio_write_list_lock.Lock();
assert(c->io == this);
c->aio_write_list_item.remove_myself();
// queue async flush waiters
map<tid_t, std::list<AioCompletionImpl*> >::iterator waiters =
aio_write_waiters.find(c->aio_write_seq);
if (waiters != aio_write_waiters.end()) {
ldout(client->cct, 20) << "found " << waiters->second.size()
<< " waiters" << dendl;
map<tid_t, std::list<AioCompletionImpl*> >::iterator waiters = aio_write_waiters.begin();
while (waiters != aio_write_waiters.end()) {
if (!aio_write_list.empty() &&
aio_write_list.front()->aio_write_seq <= waiters->first) {
ldout(client->cct, 20) << " next outstanding write is " << aio_write_list.front()->aio_write_seq
<< " <= waiter " << waiters->first
<< ", stopping" << dendl;
break;
}
ldout(client->cct, 20) << " waking waiters on seq " << waiters->first << dendl;
for (std::list<AioCompletionImpl*>::iterator it = waiters->second.begin();
it != waiters->second.end(); ++it) {
client->finisher.queue(new C_AioCompleteAndSafe(*it));
(*it)->put();
}
aio_write_waiters.erase(waiters);
} else {
ldout(client->cct, 20) << "found no waiters for tid "
<< c->aio_write_seq << dendl;
aio_write_waiters.erase(waiters++);
}
aio_write_cond.Signal();
aio_write_list_lock.Unlock();
put();
@ -109,11 +112,13 @@ void librados::IoCtxImpl::flush_aio_writes_async(AioCompletionImpl *c)
<< " completion " << c << dendl;
Mutex::Locker l(aio_write_list_lock);
tid_t seq = aio_write_seq;
ldout(client->cct, 20) << "flush_aio_writes_async waiting on tid "
<< seq << dendl;
if (aio_write_list.empty()) {
ldout(client->cct, 20) << "flush_aio_writes_async no writes. (tid "
<< seq << ")" << dendl;
client->finisher.queue(new C_AioCompleteAndSafe(c));
} else {
ldout(client->cct, 20) << "flush_aio_writes_async " << aio_write_list.size()
<< " writes in flight; waiting on tid " << seq << dendl;
c->get();
aio_write_waiters[seq].push_back(c);
}