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Merged
shinrich merged 1 commit into from
Feb 21, 2020
Merged

Another option to fix potential HTTP/2 vio stall #6409

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69 changes: 31 additions & 38 deletions proxy/http2/Http2Stream.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,13 @@ Http2Stream::main_event_handler(int event, void *edata)

Event *e = static_cast<Event *>(edata);
reentrancy_count++;
if (e == cross_thread_event) {
if (e == _read_vio_event) {
this->signal_read_event(e->callback_event);
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@masaori335 masaori335 Feb 12, 2020

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It's better to set _read_vio_event nullptr before signal_read_event() call. Otherwise, _read_vio_event->cancel() will be called when the mutex could not be locked again.

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@masaori335 masaori335 Feb 12, 2020

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[nitpicking] e->callback_event is same to event, right? Using event looks clear in these event handlers.

return 0;
} else if (e == _write_vio_event) {
this->signal_write_event(e->callback_event);
return 0;
} else if (e == cross_thread_event) {
cross_thread_event = nullptr;
} else if (e == active_event) {
event = VC_EVENT_ACTIVE_TIMEOUT;
Expand All @@ -95,41 +101,17 @@ Http2Stream::main_event_handler(int event, void *edata)
case VC_EVENT_ACTIVE_TIMEOUT:
case VC_EVENT_INACTIVITY_TIMEOUT:
if (_sm && read_vio.ntodo() > 0) {
MUTEX_TRY_LOCK(lock, read_vio.mutex, this_ethread());
if (lock.is_locked()) {
read_vio.cont->handleEvent(event, &read_vio);
} else {
if (this->_read_vio_event) {
this->_read_vio_event->cancel();
}
this->_read_vio_event = this_ethread()->schedule_imm(read_vio.cont, event, &read_vio);
}
this->signal_read_event(event);
} else if (_sm && write_vio.ntodo() > 0) {
MUTEX_TRY_LOCK(lock, write_vio.mutex, this_ethread());
if (lock.is_locked()) {
write_vio.cont->handleEvent(event, &write_vio);
} else {
if (this->_write_vio_event) {
this->_write_vio_event->cancel();
}
this->_write_vio_event = this_ethread()->schedule_imm(write_vio.cont, event, &write_vio);
}
this->signal_write_event(event);
}
break;
case VC_EVENT_WRITE_READY:
case VC_EVENT_WRITE_COMPLETE:
inactive_timeout_at = Thread::get_hrtime() + inactive_timeout;
if (e->cookie == &write_vio) {
if (write_vio.mutex && write_vio.cont && this->_sm) {
MUTEX_TRY_LOCK(lock, write_vio.mutex, this_ethread());
if (lock.is_locked()) {
write_vio.cont->handleEvent(event, &write_vio);
} else {
if (this->_write_vio_event) {
this->_write_vio_event->cancel();
}
this->_write_vio_event = this_ethread()->schedule_imm(write_vio.cont, event, &write_vio);
}
this->signal_write_event(event);
}
} else {
update_write_request(write_vio.get_reader(), INT64_MAX, true);
Expand All @@ -140,15 +122,7 @@ Http2Stream::main_event_handler(int event, void *edata)
inactive_timeout_at = Thread::get_hrtime() + inactive_timeout;
if (e->cookie == &read_vio) {
if (read_vio.mutex && read_vio.cont && this->_sm) {
MUTEX_TRY_LOCK(lock, read_vio.mutex, this_ethread());
if (lock.is_locked()) {
read_vio.cont->handleEvent(event, &read_vio);
} else {
if (this->_read_vio_event) {
this->_read_vio_event->cancel();
}
this->_read_vio_event = this_ethread()->schedule_imm(read_vio.cont, event, &read_vio);
}
signal_read_event(event);
}
} else {
this->update_read_request(INT64_MAX, true);
Expand Down Expand Up @@ -671,7 +645,26 @@ Http2Stream::signal_read_event(int event)
if (this->_read_vio_event) {
this->_read_vio_event->cancel();
}
this->_read_vio_event = this_ethread()->schedule_imm(read_vio.cont, event, &read_vio);
this->_read_vio_event = this_ethread()->schedule_in(this, retry_delay, event, &read_vio);
}
}

void
Http2Stream::signal_write_event(int event)
{
if (this->write_vio.cont == nullptr || this->write_vio.cont->mutex == nullptr || this->write_vio.op == VIO::NONE) {
return;
}

MUTEX_TRY_LOCK(lock, write_vio.cont->mutex, this_ethread());
if (lock.is_locked()) {
inactive_timeout_at = Thread::get_hrtime() + inactive_timeout;
this->write_vio.cont->handleEvent(event, &this->write_vio);
} else {
if (this->_write_vio_event) {
this->_write_vio_event->cancel();
}
this->_write_vio_event = this_ethread()->schedule_in(this, retry_delay, event, &write_vio);
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@maskit maskit Feb 12, 2020 •
edited
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If I understand this correctly, we don't need to pass write_vio because it always use THE write_vio that Http2Stream has, right?

Is retry_delay required? Should we change signal_read_event to use it too (on maybe another PR)?

Edit: I found signal_read_event already use retry_delay on this PR.

}
}

Expand Down
4 changes: 3 additions & 1 deletion proxy/http2/Http2Stream.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,8 @@ enum class Http2StreamMilestone {
class Http2Stream : public ProxyTransaction
{
public:
using super = ProxyTransaction; ///< Parent type.
const int retry_delay = HRTIME_MSECONDS(10);
using super = ProxyTransaction; ///< Parent type.

Http2Stream(Http2StreamId sid = 0, ssize_t initial_rwnd = Http2::initial_window_size);

Expand All @@ -75,6 +76,7 @@ class Http2Stream : public ProxyTransaction
void update_write_request(IOBufferReader *buf_reader, int64_t write_len, bool send_update);

void signal_read_event(int event);
void signal_write_event(int event);
void signal_write_event(bool call_update);

void restart_sending();
Expand Down