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Motivation: The commit 4759b3f ("pool: don't scan flush/restore/remove queue to get stats") introduced lock-free nearline subsistem queue statistics to improve the queue query throughout. However, the change missed the case where queue state and stats must be updated atomically. Thus, tape pools under heavy load might run into double accounting when many requests are canceled of removed files have been in the flush queue. Modification: Introduce per-queue lock that takes care that queue statistics and request state update atomically. The getXxxQueueSize has no locks as stats are used in AtomicReference Result: Queue statistics can no longer go negative and pools no longer gets stuck. Fixes: #7511 Acked-by: Lennart Sack Target: master, 12.0, 11.2 Require-book: no Require-notes: yes (cherry picked from commit 1a362eb) Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
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Motivation:
The commit 4759b3f ("pool: don't scan flush/restore/remove queue to get stats") introduced lock-free nearline subsistem queue statistics to improve the queue query throughout. However, the change missed the case where queue state and stats must be updated atomically. Thus, tape pools under heavy load might run into double accounting when many requests are canceled of removed files have been in the flush queue.
Modification:
Introduce per-queue lock that takes care that queue statistics and request state update atomically. The getXxxQueueSize has no locks as stats are used in AtomicReference
Result:
Queue statistics can no longer go negative and pools no longer gets stuck.
Fixes: #7511
Acked-by: Lennart Sack
Target: master, 12.0, 11.2
Require-book: no
Require-notes: yes
(cherry picked from commit 1a362eb)