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Prevent concurrent modification exceptions in VcnManagementService

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In order to prevent concurrent modifications from triggering an
exception in the dump, proxy it to the handler thread.

Adding locks was considered, but would require auditing all callbacks
and proxying them to the handler threads in order to ensure lock
inversion and deadlocks never occur.

Bug: 188840899
Test: FrameworksVcnTests
Test: adb shell dumpsys vcn_management
Change-Id: Ibcc4bdc06301dd77260adaa0c086529f8f524679
Merged-In: Ibcc4bdc06301dd77260adaa0c086529f8f524679
(cherry picked from commit f8ce665d9f)
This commit is contained in:
Benedict Wong
2021-05-20 16:42:42 -07:00
parent 95590e1a62
commit 5c5b485013
1 changed files with 37 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

69
services/core/java/com/android/server/VcnManagementService.java
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@@ -148,6 +148,7 @@ import java.util.concurrent.TimeUnit;
// TODO(b/180451994): ensure all incoming + outgoing calls have a cleared calling identity
public class VcnManagementService extends IVcnManagementService.Stub {
@NonNull private static final String TAG = VcnManagementService.class.getSimpleName();
private static final long DUMP_TIMEOUT_MILLIS = TimeUnit.SECONDS.toMillis(5);
public static final boolean VDBG = false; // STOPSHIP: if true
@@ -1001,46 +1002,50 @@ public class VcnManagementService extends IVcnManagementService.Stub {
final IndentingPrintWriter pw = new IndentingPrintWriter(writer, " ");
pw.println("VcnManagementService dump:");
pw.increaseIndent();
pw.println("mNetworkProvider:");
pw.increaseIndent();
mNetworkProvider.dump(pw);
pw.decreaseIndent();
pw.println();
pw.println("mTrackingNetworkCallback:");
pw.increaseIndent();
mTrackingNetworkCallback.dump(pw);
pw.decreaseIndent();
pw.println();
synchronized (mLock) {
pw.println("mLastSnapshot:");
// Post to handler thread to prevent ConcurrentModificationExceptions, and avoid lock-hell.
mHandler.runWithScissors(() -> {
pw.println("VcnManagementService dump:");
pw.increaseIndent();
mLastSnapshot.dump(pw);
pw.println("mNetworkProvider:");
pw.increaseIndent();
mNetworkProvider.dump(pw);
pw.decreaseIndent();
pw.println();
pw.println("mConfigs:");
pw.println("mTrackingNetworkCallback:");
pw.increaseIndent();
for (Entry<ParcelUuid, VcnConfig> entry : mConfigs.entrySet()) {
pw.println(entry.getKey() + ": " + entry.getValue().getProvisioningPackageName());
mTrackingNetworkCallback.dump(pw);
pw.decreaseIndent();
pw.println();
synchronized (mLock) {
pw.println("mLastSnapshot:");
pw.increaseIndent();
mLastSnapshot.dump(pw);
pw.decreaseIndent();
pw.println();
pw.println("mConfigs:");
pw.increaseIndent();
for (Entry<ParcelUuid, VcnConfig> entry : mConfigs.entrySet()) {
pw.println(entry.getKey() + ": "
+ entry.getValue().getProvisioningPackageName());
}
pw.decreaseIndent();
pw.println();
pw.println("mVcns:");
pw.increaseIndent();
for (Vcn vcn : mVcns.values()) {
vcn.dump(pw);
}
pw.decreaseIndent();
pw.println();
}
pw.decreaseIndent();
pw.println();
pw.println("mVcns:");
pw.increaseIndent();
for (Vcn vcn : mVcns.values()) {
vcn.dump(pw);
}
pw.decreaseIndent();
pw.println();
}
pw.decreaseIndent();
}, DUMP_TIMEOUT_MILLIS);
}
// TODO(b/180452282): Make name more generic and implement directly with VcnManagementService