Changeset 231663 in webkit

Timestamp:

May 10, 2018, 3:02:31 PM (8 years ago)

Author:

Chris Dumez

Message:

[iOS] Apps that are not visible may not get suspended if they trigger page loads while in the background
​https://bugs.webkit.org/show_bug.cgi?id=185318

Reviewed by Geoffrey Garen.

Whenever there is a page load going on, we take a background process assertion to delay process
suspension until this load completes. However, there is also a 3 seconds grace period after
a load is complete to allow the app to trigger a new load shortly after. This grace period was
introduced to support use cases where a visible app does loads in an offscreen view. However,
it can be abused by apps running in the background as they could trigger new page loads while
in the background to delay process suspension. This patch tightens the policy so that only
apps that are currently visible get to use this grace period. Apps that are in the background
get to finish their current load and will then get suspended.

• UIProcess/Cocoa/NavigationState.mm:

(WebKit::NavigationState::didChangeIsLoading):

Location:

trunk

Files:

• Source/WebKit/ChangeLog (modified) (1 diff)
• Source/WebKit/UIProcess/Cocoa/NavigationState.mm (modified) (1 diff)
• Tools/TestWebKitAPI/cocoa/TestWKWebView.mm (modified) (1 diff)

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2018-05-10  Chris Dumez  <cdumez@apple.com>
+
+        [iOS] Apps that are not visible may not get suspended if they trigger page loads while in the background
+        https://bugs.webkit.org/show_bug.cgi?id=185318
+
+        Reviewed by Geoffrey Garen.
+
+        Whenever there is a page load going on, we take a background process assertion to delay process
+        suspension until this load completes. However, there is also a 3 seconds grace period after
+        a load is complete to allow the app to trigger a new load shortly after. This grace period was
+        introduced to support use cases where a visible app does loads in an offscreen view. However,
+        it can be abused by apps running in the background as they could trigger new page loads while
+        in the background to delay process suspension. This patch tightens the policy so that only
+        apps that are currently visible get to use this grace period. Apps that are in the background
+        get to finish their current load and will then get suspended.
+
+        * UIProcess/Cocoa/NavigationState.mm:
+        (WebKit::NavigationState::didChangeIsLoading):
+
 2018-05-10  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebKit/UIProcess/Cocoa/NavigationState.mm

@@ -1158 +1158 @@
 #if PLATFORM(IOS)
     if (m_webView->_page->pageLoadState().isLoading()) {
-        if (m_releaseActivityTimer.isActive())
+        if (m_releaseActivityTimer.isActive()) {
+            RELEASE_LOG_IF(m_webView->_page->isAlwaysOnLoggingAllowed(), ProcessSuspension, "%p - A new page load started while the UIProcess was still holding a page load background assertion", this);
             m_releaseActivityTimer.stop();
-        else {
+        } else {
             RELEASE_LOG_IF(m_webView->_page->isAlwaysOnLoggingAllowed(), ProcessSuspension, "%p - UIProcess is taking a background assertion because a page load started", this);
             ASSERT(!m_activityToken);
             m_activityToken = m_webView->_page->process().throttler().backgroundActivityToken();
         }
-    } else {
-        // Delay releasing the background activity for 3 seconds to give the application a chance to start another navigation
-        // before suspending the WebContent process <rdar://problem/27910964>.
-        m_releaseActivityTimer.startOneShot(3_s);
+    } else if (m_activityToken) {
+        if (m_webView._isBackground)
+            releaseNetworkActivityToken();
+        else {
+            // The application is visible so we delay releasing the background activity for 3 seconds to give it a chance to start another navigation
+            // before suspending the WebContent process <rdar://problem/27910964>.
+            RELEASE_LOG_IF(m_webView->_page->isAlwaysOnLoggingAllowed(), ProcessSuspension, "%p - Page load completed and UIProcess will be releasing background assertion soon unless a new load starts", this);
+            m_releaseActivityTimer.startOneShot(3_s);
+        }
     }
 #endif

trunk/Tools/TestWebKitAPI/cocoa/TestWKWebView.mm

@@ -50 +50 @@
 SOFT_LINK_FRAMEWORK(UIKit)
 SOFT_LINK_CLASS(UIKit, UIWindow)
+
+@implementation WKWebView (WKWebViewTestingQuicks)
+
+// TestWebKitAPI is currently not a UIApplication so we are unable to track if it is in
+// the background or not (https://bugs.webkit.org/show_bug.cgi?id=175204). This can
+// cause our processes to get suspended on iOS. We work around this by having
+// WKWebView._isBackground always return NO in the context of API tests.
+- (BOOL)_isBackground
+{
+    return NO;
+}
+@end
 #endif