jenkins-bot has submitted this change and it was merged.
Change subject: Avoid self-deadlocks in MessageCache::replace()
......................................................................
Avoid self-deadlocks in MessageCache::replace()
* This makes use of the $rclass flag in BagOStuff
Bug: T109183
Change-Id: I305f51e744aac53876e5865f860c282aa2efbd8b
---
M includes/cache/MessageCache.php
1 file changed, 16 insertions(+), 3 deletions(-)
Approvals:
Ori.livneh: Looks good to me, approved
jenkins-bot: Verified
diff --git a/includes/cache/MessageCache.php b/includes/cache/MessageCache.php
index f11a648..9aac37a 100644
--- a/includes/cache/MessageCache.php
+++ b/includes/cache/MessageCache.php
@@ -346,7 +346,7 @@
# Wait for the other thread to
finish, then retry. Normally,
# the memcached get() will then
yeild the other thread's result.
$where[] = 'waited for other
thread to complete';
- $this->mMemc->getScopedLock(
$cacheKey, self::WAIT_SEC, self::LOCK_TTL );
+ $this->getReentrantScopedLock(
$cacheKey );
}
}
}
@@ -400,7 +400,7 @@
# If this lock fails, it doesn't really matter, it just means
the
# write is potentially non-atomic, e.g. the results of a
replace()
# may be discarded.
- $mainUnlocker = $memCache->getScopedLock( $cacheKey,
self::WAIT_SEC, self::LOCK_TTL );
+ $mainUnlocker = $this->getReentrantScopedLock( $cacheKey );
if ( !$mainUnlocker ) {
$where[] = 'could not acquire main lock';
}
@@ -548,8 +548,13 @@
return;
}
+ # Note that if the cache is volatile, load() may trigger a DB
fetch.
+ # In that case we reenter/reuse the existing cache key lock to
avoid
+ # a self-deadlock. This is safe as no reads happen *directly*
in this
+ # method between getReentrantScopedLock() and load() below.
There is
+ # no risk of data "changing under our feet" for replace().
$cacheKey = wfMemcKey( 'messages', $code );
- $scopedLock = $this->mMemc->getScopedLock( $cacheKey,
self::WAIT_SEC, self::LOCK_TTL );
+ $scopedLock = $this->getReentrantScopedLock( $cacheKey );
$this->load( $code, self::FOR_UPDATE );
$titleKey = wfMemcKey( 'messages', 'individual', $title );
@@ -674,6 +679,14 @@
}
/**
+ * @param string $key A language message cache key that stores blobs
+ * @return null|ScopedCallback
+ */
+ protected function getReentrantScopedLock( $key ) {
+ return $this->mMemc->getScopedLock( $key, self::WAIT_SEC,
self::LOCK_TTL, __METHOD__ );
+ }
+
+ /**
* Get a message from either the content language or the user language.
*
* First, assemble a list of languages to attempt getting the message
from. This
--
To view, visit https://gerrit.wikimedia.org/r/233063
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: merged
Gerrit-Change-Id: I305f51e744aac53876e5865f860c282aa2efbd8b
Gerrit-PatchSet: 3
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <[email protected]>
Gerrit-Reviewer: Legoktm <[email protected]>
Gerrit-Reviewer: Ori.livneh <[email protected]>
Gerrit-Reviewer: jenkins-bot <>
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