Major Description
The related code here:
void
UnixNetVConnection::reenable(VIO *vio)
{
if (STATE_FROM_VIO(vio)->enabled)
return;
set_enabled(vio);
if (!thread)
return;
EThread *t = vio->mutex->thread_holding;
ink_assert(t == this_ethread());
ink_release_assert(!closed);
if (nh->mutex->thread_holding == t) {
...
MUTEX_TRY_LOCK(lock, nh->mutex, t);
if (!lock.is_locked()) {
if (vio == &read.vio) {
if (!read.in_enabled_list) { // -----------> the condition check is not atomic
read.in_enabled_list = 1; // -----------> the variable set is not atomic
nh->read_enable_list.push(this);
}
} else {
if (!write.in_enabled_list) { // -----------> the write side
write.in_enabled_list = 1; // -----------> the write side
nh->write_enable_list.push(this);
}
}
if (nh->trigger_event && nh->trigger_event->ethread->signal_hook)
nh->trigger_event->ethread->signal_hook(nh->trigger_event->ethread);
} else {
...
}
}
}
Due to the unstable condition check code, the nh->read_enable_list.push(this) would push a netvc into atomic queue that is already inside a queue.
It leads the elements in atomic queue after the netvc will be lost.
