attempt to kill slave thread can cause server hanging

[Seppo Jaakola]

High priority threads (slave threads, replaying threads, total order isolation threads) are not protected from kill signal and attempt to kill high priority thread can cause server to hang. One such a scenario is reported in MariaDB project: https://mariadb.atlassian.net/browse/MDEV-3924

As a fix, high priority threads should be protected from kill.

[Seppo Jaakola (seppo-jaakola)]

The fix will prevent kill command for appliers, aborter thread, replaying local connections or local connections in commit state
Fix pushed in revision: http://bazaar.launchpad.net/~codership/codership-mysql/5.5-23/revision/3870

[Raghavendra D Prabhu (raghavendra-prabhu)]

The fix of this issue is not present in 5.6 tree, hence adding 5.6 component.

@Codership,

This is required for 5.6 too right?

[Seppo Jaakola (seppo-jaakola)]

Added 5.6 branch in work queue, merge will appear within short

[Seppo Jaakola (seppo-jaakola)]

Fix merged into wsrep-5.6 in revision: http://bazaar.launchpad.net/~codership/codership-mysql/5.6/revision/3973

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXC-1271