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Posted to dev@hawq.apache.org by wengyanqing <gi...@git.apache.org> on 2015/12/02 04:15:06 UTC
[GitHub] incubator-hawq pull request: modify metadata cache read lock logic
GitHub user wengyanqing opened a pull request:
https://github.com/apache/incubator-hawq/pull/146
modify metadata cache read lock logic
modify metadata cache lock logic when check item exists
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/wengyanqing/incubator-hawq metadatacache
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-hawq/pull/146.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #146
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commit b58e893ed37978249cbb279d398eac73cf002880
Author: ivan <iw...@pivotal.io>
Date: 2015-12-02T03:06:37Z
modify metadata cache read lock logic
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[GitHub] incubator-hawq pull request: modify metadata cache read lock logic
Posted by gcaragea <gi...@git.apache.org>.
Github user gcaragea commented on a diff in the pull request:
https://github.com/apache/incubator-hawq/pull/146#discussion_r46597216
--- Diff: src/backend/cdb/cdbmetadatacache.c ---
@@ -619,6 +619,9 @@ BlockLocation *GetHdfsFileBlockLocations(const HdfsFileInfo *file_info, uint64_t
if (cache_entry->block_num <= 1)
{
// only one file, re-fetch
+ LWLockRelease(MetadataCacheLock);
+
+ LWLockAcquire(MetadataCacheLock, LW_EXCLUSIVE);
--- End diff --
Can this create deadlock situations? Upgrading locks usually is a tricky situation, can lead to a situation where:
- proc A has SHARED lock on foo and bar
- proc B has SHARED lock on foo and bar
- proc A requests EXCLUSIVE lock on foo and gets it
- proc B requests EXCLUSIVE lock on bar and gets it
- proc A requests EXCLUSIVE lock on bar and waits
- proc B requests EXCLUSIVE lock on foo and waits - deadlock
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[GitHub] incubator-hawq pull request: modify metadata cache read lock logic
Posted by linwen <gi...@git.apache.org>.
Github user linwen commented on the pull request:
https://github.com/apache/incubator-hawq/pull/146#issuecomment-161167070
+1
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[GitHub] incubator-hawq pull request: modify metadata cache read lock logic
Posted by wengyanqing <gi...@git.apache.org>.
Github user wengyanqing commented on a diff in the pull request:
https://github.com/apache/incubator-hawq/pull/146#discussion_r46654739
--- Diff: src/backend/cdb/cdbmetadatacache.c ---
@@ -619,6 +619,9 @@ BlockLocation *GetHdfsFileBlockLocations(const HdfsFileInfo *file_info, uint64_t
if (cache_entry->block_num <= 1)
{
// only one file, re-fetch
+ LWLockRelease(MetadataCacheLock);
+
+ LWLockAcquire(MetadataCacheLock, LW_EXCLUSIVE);
--- End diff --
Hi George,
Thanks for your comment. It only has one lock (MetadataCacheLock) and one resource (MetadataCache) which lock on, so it should not cause dead lock.
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[GitHub] incubator-hawq pull request: modify metadata cache read lock logic
Posted by wengyanqing <gi...@git.apache.org>.
Github user wengyanqing closed the pull request at:
https://github.com/apache/incubator-hawq/pull/146
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