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fixes a stream deadlock multiple ways #8

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merged 3 commits into from
Oct 22, 2019
Merged

fixes a stream deadlock multiple ways #8

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8912b9d
fix(stream): avoid taking the receive lock while holding the state lock
Stebalien Oct 22, 2019
1f87e6e
chore: really, just avoid holding the state lock longer than we need to
Stebalien Oct 22, 2019
6264803
chore: avoid taking a lock while holding a lock
Stebalien Oct 22, 2019
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28 changes: 14 additions & 14 deletions stream.go
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Original file line number Diff line number Diff line change
Expand Up @@ -77,22 +77,22 @@ func (s *Stream) Read(b []byte) (n int, err error) {
defer asyncNotify(s.recvNotifyCh)
START:
s.stateLock.Lock()
switch s.state {
state := s.state
s.stateLock.Unlock()

switch state {
case streamRemoteClose:
fallthrough
case streamClosed:
s.recvLock.Lock()
if s.recvBuf.Len() == 0 {
s.recvLock.Unlock()
s.stateLock.Unlock()
empty := s.recvBuf.Len() == 0
s.recvLock.Unlock()
if empty {
return 0, io.EOF
}
s.recvLock.Unlock()
case streamReset:
s.stateLock.Unlock()
return 0, ErrConnectionReset
}
s.stateLock.Unlock()

// If there is no data available, block
s.recvLock.Lock()
Expand Down Expand Up @@ -143,17 +143,17 @@ func (s *Stream) write(b []byte) (n int, err error) {

START:
s.stateLock.Lock()
switch s.state {
state := s.state
s.stateLock.Unlock()

switch state {
case streamLocalClose:
fallthrough
case streamClosed:
s.stateLock.Unlock()
return 0, ErrStreamClosed
case streamReset:
s.stateLock.Unlock()
return 0, ErrConnectionReset
}
s.stateLock.Unlock()

// If there is no data available, block
window := atomic.LoadUint32(&s.sendWindow)
Expand Down Expand Up @@ -208,14 +208,14 @@ func (s *Stream) sendFlags() uint16 {
// sendWindowUpdate potentially sends a window update enabling
// further writes to take place. Must be invoked with the lock.
func (s *Stream) sendWindowUpdate() error {
// Determine the flags if any
flags := s.sendFlags()

// Determine the delta update
max := s.session.config.MaxStreamWindowSize
s.recvLock.Lock()
delta := (max - uint32(s.recvBuf.Len())) - s.recvWindow

// Determine the flags if any
flags := s.sendFlags()

// Check if we can omit the update
if delta < (max/2) && flags == 0 {
s.recvLock.Unlock()
Expand Down