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Commit 6b9c230d authored by Mårten Kongstad's avatar Mårten Kongstad Committed by Todd Kennedy
Browse files

Update comments now that mPackages is no longer a lock 

Commit 865fd3a5 'mPackages is not a lock!' introduced a new object
mLock for locking the package manager, instead of relying on mPackages.
Update the comments to reflect this.

Test: builds
Change-Id: I287d4c8ff22c49a6e0924e4ad4530376e41ef196
parent 5741927f

services/core/java/com/android/server/pm/PackageManagerService.java

+14 −14
Original line number Diff line number Diff line
@@ -378,14 +378,14 @@ import java.util.function.Predicate; 
 * <p>

 * Internally there are two important locks:

 * <ul>

 * <li>{@link #mPackages} is used to guard all in-memory parsed package details

 * <li>{@link #mLock} is used to guard all in-memory parsed package details

 * and other related state. It is a fine-grained lock that should only be held

 * momentarily, as it's one of the most contended locks in the system.

 * <li>{@link #mInstallLock} is used to guard all {@code installd} access, whose

 * operations typically involve heavy lifting of application data on disk. Since

 * {@code installd} is single-threaded, and it's operations can often be slow,

 * this lock should never be acquired while already holding {@link #mPackages}.

 * Conversely, it's safe to acquire {@link #mPackages} momentarily while already

 * this lock should never be acquired while already holding {@link #mLock}.

 * Conversely, it's safe to acquire {@link #mLock} momentarily while already

 * holding {@link #mInstallLock}.

 * </ul>

 * Many internal methods rely on the caller to hold the appropriate locks, and
@@ -394,8 +394,8 @@ import java.util.function.Predicate; 
 * <li>fooLI(): the caller must hold {@link #mInstallLock}

 * <li>fooLIF(): the caller must hold {@link #mInstallLock} and the package

 * being modified must be frozen

 * <li>fooLPr(): the caller must hold {@link #mPackages} for reading

 * <li>fooLPw(): the caller must hold {@link #mPackages} for writing

 * <li>fooLPr(): the caller must hold {@link #mLock} for reading

 * <li>fooLPw(): the caller must hold {@link #mLock} for writing

 * </ul>

 * <p>

 * Because this class is very central to the platform's security; please run all
@@ -669,7 +669,7 @@ public class PackageManagerService extends IPackageManager.Stub 














    // Lock for global state used when modifying package state or settings.















    // Methods that must be called with this lock held have













    // the suffix "Locked". Some methods may use the legacy the suffix "LP"













    // the suffix "Locked". Some methods may use the legacy suffix "LP"















    final Object mLock;





























    // Keys are String (package name), values are Package.










@@ -6531,13 +6531,13 @@ public class PackageManagerService extends IPackageManager.Stub













    }





























    // TODO: handle preferred activities missing while user has amnesia













    /** <b>must not hold {@link #mPackages}</b> */













    /** <b>must not hold {@link #mLock}</b> */















    ResolveInfo findPreferredActivityNotLocked(Intent intent, String resolvedType, int flags,















            List<ResolveInfo> query, int priority, boolean always,















            boolean removeMatches, boolean debug, int userId) {















        if (Thread.holdsLock(mLock)) {















            Slog.wtf(TAG, "Calling thread " + Thread.currentThread().getName()













                    + " is holding mPackages", new Throwable());













                    + " is holding mLock", new Throwable());















        }















        if (!mUserManager.exists(userId)) return null;















        final int callingUid = Binder.getCallingUid();










@@ -16196,7 +16196,7 @@ public class PackageManagerService extends IPackageManager.Stub













    /**















     * On successful install, executes remaining steps after commit completes and the package lock















     * is released. These are typically more expensive or require calls to installd, which often













     * locks on {@link #mPackages}.













     * locks on {@link #mLock}.















     */















    private void executePostCommitSteps(CommitRequest commitRequest) {















        for (ReconciledPackage reconciledPkg : commitRequest.reconciledPackages.values()) {










@@ -19873,11 +19873,11 @@ public class PackageManagerService extends IPackageManager.Stub













        return null;















    }



























    /** <b>must not hold {@link #mPackages}</b> */













    /** <b>must not hold {@link #mLock}</b> */















    private void updateDefaultHomeNotLocked(SparseBooleanArray userIds) {















        if (Thread.holdsLock(mLock)) {















            Slog.wtf(TAG, "Calling thread " + Thread.currentThread().getName()













                    + " is holding mPackages", new Throwable());













                    + " is holding mLock", new Throwable());















        }















        for (int i = userIds.size() - 1; i >= 0; --i) {















            final int userId = userIds.keyAt(i);









@@ -19886,14 +19886,14 @@ public class PackageManagerService extends IPackageManager.Stub













    }





























    /**













     * <b>must not hold {@link #mPackages}</b>













     * <b>must not hold {@link #mLock}</b>















     *















     * @return Whether the ACTION_PREFERRED_ACTIVITY_CHANGED broadcast has been scheduled.















     */















    private boolean updateDefaultHomeNotLocked(int userId) {















        if (Thread.holdsLock(mLock)) {















            Slog.wtf(TAG, "Calling thread " + Thread.currentThread().getName()













                    + " is holding mPackages", new Throwable());













                    + " is holding mLock", new Throwable());















        }















        if (!mSystemReady) {















            // We might get called before system is ready because of package changes etc, but










@@ -21824,7 +21824,7 @@ public class PackageManagerService extends IPackageManager.Stub













     * will try recovering system apps by wiping data; third-party app data is















     * left intact.















     * <p>













     * <em>Note: To avoid a deadlock, do not call this method with {@code mPackages} lock held</em>













     * <em>Note: To avoid a deadlock, do not call this method with {@code mLock} lock held</em>















     */















    private void prepareAppDataAfterInstallLIF(PackageParser.Package pkg) {















        final PackageSetting ps;