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https://issues.apache.org/jira/browse/TS-5076?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Phil Sorber resolved TS-5076.
-----------------------------
Resolution: Fixed
Marking this resolved since it's in master.
> NetVC is lost from read or write enable_list
> --------------------------------------------
>
> Key: TS-5076
> URL: https://issues.apache.org/jira/browse/TS-5076
> Project: Traffic Server
> Issue Type: Bug
> Components: Network
> Reporter: Oknet Xu
> Assignee: Oknet Xu
> Fix For: 6.2.1, 7.1.0
>
> Time Spent: 3.5h
> Remaining Estimate: 0h
>
> The related code here:
> {code}
> 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 {
> ...
> }
> }
> }
> {code}
> 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.
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