Fix deadlock when running backup #6006
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A deadlock occurs under write load if a backup is run in between the time when a snapshot compactions has snapshotted the cache and successfully written it to disk. The issus is that the second snapshot call will block on the commit lock while it is holding the engine write lock. This causes all writes to block as well as prevents the currently runnign snapshot compaction from completing because it needs to acquire a read-lock. This PR removes the commit lock and just returns an error if a snapshot is in progress to all any locks being held to be released. The caller can determine whether to retry or giveup.
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👍 LGTM |
jwilder
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Mar 14, 2016
Fix deadlock when running backup
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Oops, apologies @jwilder for not spotting this consequence. |
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A deadlock occurs under write load if a backup is run in between the
time when a snapshot compactions has snapshotted the cache and successfully
written it to disk. The issus is that the second snapshot call will block
on the commit lock while it is holding the engine write lock. This causes
all writes to block as well as prevents the currently runnign snapshot
compaction from completing because it needs to acquire a read-lock.
This PR removes the commit lock and just returns an error if a snapshot is
in progress to all any locks being held to be released. The caller can determine
whether to retry or giveup.