Respond to CR.

Signal/src/ViewControllers/OWSLinkDeviceViewController.m

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import "OWSLinkDeviceViewController.h"
@@ -147,7 +147,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)provisionWithParser:(OWSDeviceProvisioningURLParser *)parser
 {
     // Optimistically set this flag.
-    [OWSDeviceManager.sharedManager setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
+    [OWSDeviceManager.sharedManager setMayHaveLinkedDevices];
 
     ECKeyPair *_Nullable identityKeyPair = [[OWSIdentityManager sharedManager] identityKeyPair];
     OWSAssert(identityKeyPair);

Signal/src/ViewControllers/OWSLinkedDevicesTableViewController.m

@@ -146,9 +146,7 @@ int const OWSLinkedDevicesTableViewControllerSectionAddDevice = 1;
             if (devices.count > 1) {
                 // Setting this flag here shouldn't be necessary, but we do so
                 // because the "cost" is low and it will improve robustness.
-                [OWSDeviceManager.sharedManager
+                [OWSDeviceManager.sharedManager setMayHaveLinkedDevices];
-                    setMayHaveLinkedDevices:YES
-                               dbConnection:[[TSStorageManager sharedManager] newDatabaseConnection]];
             }
 
             if (devices.count > [OWSDevice numberOfKeysInCollection]) {

SignalServiceKit/src/Devices/OWSDevice.h

@@ -16,8 +16,7 @@ extern uint32_t const OWSDevicePrimaryDeviceId;
 + (instancetype)sharedManager;
 
 - (BOOL)mayHaveLinkedDevices:(YapDatabaseConnection *)dbConnection;
-- (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection;
+- (void)setMayHaveLinkedDevices;
-- (void)setMayHaveLinkedDevices:(BOOL)value transaction:(YapDatabaseReadWriteTransaction *)transaction;
 
 - (BOOL)hasReceivedSyncMessageInLastSeconds:(NSTimeInterval)intervalSeconds;
 - (void)setHasReceivedSyncMessage;

SignalServiceKit/src/Devices/OWSDevice.m

@@ -19,6 +19,7 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
 
 @interface OWSDeviceManager ()
 
+@property (atomic, nullable) NSNumber *mayHaveLinkedDevicesCached;
 @property (atomic) NSDate *lastReceivedSyncMessage;
 
 @end
@@ -46,27 +47,32 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
 {
     OWSAssert(dbConnection);
 
-    return [dbConnection boolForKey:kTSStorageManager_MayHaveLinkedDevices
+    // We don't bother synchronizing around
-                       inCollection:kTSStorageManager_OWSDeviceCollection
+    if (!self.mayHaveLinkedDevicesCached) {
-                       defaultValue:NO];
+        self.mayHaveLinkedDevicesCached = @([dbConnection boolForKey:kTSStorageManager_MayHaveLinkedDevices
-}
+                                                        inCollection:kTSStorageManager_OWSDeviceCollection
-
+                                                        defaultValue:YES]);
-- (void)setMayHaveLinkedDevices:(BOOL)value dbConnection:(YapDatabaseConnection *)dbConnection
+    }
-{
-    OWSAssert(dbConnection);
 
-    [dbConnection asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
+    return [self.mayHaveLinkedDevicesCached boolValue];
-        [self setMayHaveLinkedDevices:value transaction:transaction];
-    }];
 }
 
-- (void)setMayHaveLinkedDevices:(BOOL)value transaction:(YapDatabaseReadWriteTransaction *)transaction
+- (void)setMayHaveLinkedDevices
 {
-    OWSAssert(transaction);
+    if (self.mayHaveLinkedDevicesCached != nil && self.mayHaveLinkedDevicesCached.boolValue) {
+        // Skip redundant writes.
+        return;
+    }
 
-    [transaction setObject:@(value)
+    self.mayHaveLinkedDevicesCached = @(YES);
-                    forKey:kTSStorageManager_MayHaveLinkedDevices
+
-              inCollection:kTSStorageManager_OWSDeviceCollection];
+    // Note that we write async to avoid opening transactions within transactions.
+    [TSStorageManager.sharedManager.newDatabaseConnection
+        asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *_Nonnull transaction) {
+            [transaction setObject:@(YES)
+                            forKey:kTSStorageManager_MayHaveLinkedDevices
+                      inCollection:kTSStorageManager_OWSDeviceCollection];
+        }];
 }
 
 - (BOOL)hasReceivedSyncMessageInLastSeconds:(NSTimeInterval)intervalSeconds
@@ -77,6 +83,8 @@ NSString *const kTSStorageManager_MayHaveLinkedDevices = @"kTSStorageManager_May
 - (void)setHasReceivedSyncMessage
 {
     self.lastReceivedSyncMessage = [NSDate new];
+
+    [self setMayHaveLinkedDevices];
 }
 
 @end

SignalServiceKit/src/Messages/OWSMessageManager.m

@@ -278,7 +278,6 @@ NS_ASSUME_NONNULL_BEGIN
             [self handleIncomingEnvelope:envelope withSyncMessage:content.syncMessage transaction:transaction];
 
             [[OWSDeviceManager sharedManager] setHasReceivedSyncMessage];
-            [OWSDeviceManager.sharedManager setMayHaveLinkedDevices:YES transaction:transaction];
         } else if (content.hasDataMessage) {
             [self handleIncomingEnvelope:envelope withDataMessage:content.dataMessage transaction:transaction];
         } else if (content.hasCallMessage) {

SignalServiceKit/src/Messages/OWSMessageSender.m

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import "OWSMessageSender.h"
@@ -1090,7 +1090,7 @@ NSString *const OWSMessageSenderRateLimitedException = @"RateLimitedException";
     if (missingDevices.count > 0) {
         NSString *localNumber = [TSAccountManager localNumber];
         if ([localNumber isEqualToString:recipient.uniqueId]) {
-            [OWSDeviceManager.sharedManager setMayHaveLinkedDevices:YES dbConnection:self.dbConnection];
+            [OWSDeviceManager.sharedManager setMayHaveLinkedDevices];
         }
     }