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Bug 511677: Mitigate deadlock closing project during indexer job

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A deadlock can occur if a project is closing and an indexing job is
running.
There is a patch on Gerrit that reproduces the lock all the time:
https://git.eclipse.org/r/#/c/90603

Thread #1, closes the project (*workspace lock*), removes the binary
parser for this project. Around the same time...

Thread #2, is just about to start indexing the project
(PDOMRebuildTask).
  It visits the C model to collect source files. Because the binary
parser was removed, it reloads the project description, which triggers a
listener (CExternalSettingsManager) to get a *workspace lock*.

Thread #1 then blocks on cancelling the indexer, which will never happen
because it is blocked on getting the workspace lock.

This deadlock could happen for any code being called by the indexer
thread that gets a workspace lock before the indexer cancels itself.
Because so much code can be hooked up to the C model (extensions,
listeners, etc), it is difficult to guarantee that this will not happen.

- Possible option 1. Changing CExternalSettingsManager to execute
asynchronously (Job) breaks other code that expect the operation to be
synchronous. Doing this also does not guarantee that other code will not
get a workspace lock.

- Possible option 2. Cancelling the indexer before the binary parser is
removed from the map: does not break any tests but only cover this
particular case of the binary parser triggering the project description
reload. Any other code that triggers a project description reload (and
workspace lock) will still be an issue.

Option 2, although incomplete, seems the safest and more reasonable at
this point. Judging by the comments in bug 327126, to fix this properly
would require quite a big effort that I'm not sure anyone would do.

Change-Id: Ida7b45558e4430bc5cc9a1eb5ef25e8d19487c31
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
This commit is contained in:
Marc-Andre Laperle 2017-02-10 12:55:11 -05:00 • committed by Gerrit Code Review @ Eclipse.org
parent 8c02478e71
commit 3f0e34177c
1 changed files with 4 additions and 4 deletions
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8
core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/model/CModelManager.java
View file

@ -1400,21 +1400,21 @@ public class CModelManager implements IResourceChangeListener, IContentTypeChang
}
private void preDeleteProject(IProject project) {
// Stop indexing jobs for this project
CCoreInternals.getPDOMManager().preDeleteProject(create(project));
// Remove binary parsers
binaryParsersMap.remove(project);
// Stop the binary runner for this project
removeBinaryRunner(project);
// Stop indexing jobs for this project
CCoreInternals.getPDOMManager().preDeleteProject(create(project));
}
private void preCloseProject(IProject project) {
// Stop indexing jobs for this project
CCoreInternals.getPDOMManager().preCloseProject(create(project));
// Remove binary parsers
binaryParsersMap.remove(project);
// Stop the binary runner for this project
removeBinaryRunner(project);
// Stop indexing jobs for this project
CCoreInternals.getPDOMManager().preCloseProject(create(project));
}
public IWorkingCopy[] getSharedWorkingCopies(IBufferFactory factory) {