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[stable19] Fix releasing a shared lock multiple times #21710

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Merged
MorrisJobke merged 2 commits into from
Jul 6, 2020
Merged

[stable19] Fix releasing a shared lock multiple times #21710

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392df2e
Fix releasing a shared lock multiple times
jvsalo May 24, 2020
3f1b055
In LockPlugin, only release a lock if it was acquired
jvsalo May 24, 2020
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Fix releasing a shared lock multiple times 
Signed-off-by: Jaakko Salo <[email protected]>
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@jvsalo @backportbot
jvsalo authored and backportbot[bot] committed Jul 6, 2020
commit 392df2eaf4ae41530b4743305a765a7ec173e92a
6 changes: 5 additions & 1 deletion lib/private/Lock/MemcacheLockingProvider.php
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Original file line number Diff line number Diff line change
Expand Up @@ -94,8 +94,12 @@ public function acquireLock(string $path, int $type) {
*/
public function releaseLock(string $path, int $type) {
if ($type === self::LOCK_SHARED) {
$ownSharedLockCount = $this->getOwnSharedLockCount($path);
$newValue = 0;
if ($this->getOwnSharedLockCount($path) === 1) {
if ($ownSharedLockCount === 0) { // if we are not holding the lock, don't try to release it
return;
}
if ($ownSharedLockCount === 1) {
$removed = $this->memcache->cad($path, 1); // if we're the only one having a shared lock we can remove it in one go
if (!$removed) { //someone else also has a shared lock, decrease only
$newValue = $this->memcache->dec($path);
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