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Attempt to fix deadlock on saveOverrides

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Currently, the lock on mChanges is held continuously while saving the
changes to disk, however if the serialization triggers an OomAdjustLSP,
that triggers yet another call to the compat framework - causing a
deadlock.
Currently, OomAdjust happens during XML serialisation, so releasing the
lock after we've collected all the data should fix the deadlock, however
there could be issues if OomAdjust happens while collecting the
overrides themselves. That seems somewhat unlikely, and would likely
signal a larger issue.

Test: atest CompatConfigTest
Bug: 190611974
Change-Id: I01e4802baeecf2757044609b91b7b7a40e728d4e
This commit is contained in:
Andrei Onea
2021-06-17 14:15:03 +00:00
parent 3d44d6ed95
commit d23af5ed30
1 changed files with 14 additions and 12 deletions
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26
services/core/java/com/android/server/compat/CompatConfig.java
View File

@@ -257,8 +257,8 @@ final class CompatConfig {
addChange(c);
}
c.addPackageOverride(packageName, overrides, allowedState, versionCode);
invalidateCache();
}
invalidateCache();
return alreadyKnown;
}
@@ -379,9 +379,9 @@ final class CompatConfig {
CompatChange change = mChanges.valueAt(i);
removeOverrideUnsafe(change, packageName, versionCode);
}
saveOverrides();
invalidateCache();
}
saveOverrides();
invalidateCache();
}
/**
@@ -626,7 +626,18 @@ final class CompatConfig {
if (mOverridesFile == null) {
return;
}
Overrides overrides = new Overrides();
synchronized (mChanges) {
List<ChangeOverrides> changeOverridesList = overrides.getChangeOverrides();
for (int idx = 0; idx < mChanges.size(); ++idx) {
CompatChange c = mChanges.valueAt(idx);
ChangeOverrides changeOverrides = c.saveOverrides();
if (changeOverrides != null) {
changeOverridesList.add(changeOverrides);
}
}
}
synchronized (mOverridesFile) {
// Create the file if it doesn't already exist
try {
mOverridesFile.createNewFile();
@@ -636,15 +647,6 @@ final class CompatConfig {
}
try (PrintWriter out = new PrintWriter(mOverridesFile)) {
XmlWriter writer = new XmlWriter(out);
Overrides overrides = new Overrides();
List<ChangeOverrides> changeOverridesList = overrides.getChangeOverrides();
for (int idx = 0; idx < mChanges.size(); ++idx) {
CompatChange c = mChanges.valueAt(idx);
ChangeOverrides changeOverrides = c.saveOverrides();
if (changeOverrides != null) {
changeOverridesList.add(changeOverrides);
}
}
XmlWriter.write(writer, overrides);
} catch (IOException e) {
Slog.e(TAG, e.toString());