pgsql: Cancel CV sleep during subtransaction abort.

Cancel CV sleep during subtransaction abort.

Generally, error recovery paths that need to do things like
LWLockReleaseAll and pgstat_report_wait_end also need to call
ConditionVariableCancelSleep, but AbortSubTransaction was missed.

Since subtransaction abort might destroy up the DSM segment that
contains the ConditionVariable stored in cv_sleep_target, this
can result in a crash for anything using condition variables.

Reported and diagnosed by Andres Freund.

Discussion: http://postgr.es/m/20171221110048.rxk6464azzl5t2fi@alap3.anarazel.de

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f3decdc94ea3dea05715325757db7b0295672bbe

Modified Files
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src/backend/access/transam/xact.c | 3 +++
1 file changed, 3 insertions(+)