Discard cached processes when clearing website data store

https://bugs.webkit.org/show_bug.cgi?id=194894

Reviewed by Chris Dumez.

Source/WebKit:

Clear the process cache when clearing the website data store so that there is no way to infer
which site the user had visited by observing for which sites WebContent processes had been cached.

There is one sublty in WebsiteDataStore::removeData that we have to delay the clearing of
the web process cache until the next run loop because SuspendedPageProxy::~SuspendedPageProxy
invokes WebProcessProxy::maybeShutDown in the next run loop. We also have to disable the process
cache during this time as it would otherwise trigger the responsiveness check of WebContent process
can take arbitrarily long time.

* UIProcess/API/Cocoa/WKProcessPool.mm:
(-[WKProcessPool _processCacheCapacity]): Added for testing.
* UIProcess/API/Cocoa/WKProcessPoolPrivate.h:
* UIProcess/WebProcessCache.cpp:
(WebKit::WebProcessCache::addProcess): Avoid adding web processes to the cache while the suspended
pages are being cleared.
* UIProcess/WebProcessCache.h:
(WebKit::WebProcessCache::disabled const): Added.
(WebKit::WebProcessCache::setDisabled): Added.
* UIProcess/WebProcessPool.cpp:
(WebKit::WebProcessPool::handleMemoryPressureWarning):
(WebKit::WebProcessPool::clearSuspendedPages): Added.
* UIProcess/WebProcessPool.h:
* UIProcess/WebsiteData/WebsiteDataStore.cpp:
(WebKit::WebsiteDataStore::removeData):

Tools:

Added a test case.

* TestWebKitAPI/Tests/WebKitCocoa/ProcessSwapOnNavigation.mm:
(TestWebKitAPI.ProcessSwap.NumberOfCachedProcesses): Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@241928 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Author: [email protected]

Source/WebKit/ChangeLog

@@ -1,3 +1,35 @@
+2019-02-21  Ryosuke Niwa  <[email protected]>
+
+        Discard cached processes when clearing website data store
+        https://bugs.webkit.org/show_bug.cgi?id=194894
+
+        Reviewed by Chris Dumez.
+
+        Clear the process cache when clearing the website data store so that there is no way to infer
+        which site the user had visited by observing for which sites WebContent processes had been cached.
+
+        There is one sublty in WebsiteDataStore::removeData that we have to delay the clearing of
+        the web process cache until the next run loop because SuspendedPageProxy::~SuspendedPageProxy
+        invokes WebProcessProxy::maybeShutDown in the next run loop. We also have to disable the process
+        cache during this time as it would otherwise trigger the responsiveness check of WebContent process
+        can take arbitrarily long time.
+
+        * UIProcess/API/Cocoa/WKProcessPool.mm:
+        (-[WKProcessPool _processCacheCapacity]): Added for testing.
+        * UIProcess/API/Cocoa/WKProcessPoolPrivate.h:
+        * UIProcess/WebProcessCache.cpp:
+        (WebKit::WebProcessCache::addProcess): Avoid adding web processes to the cache while the suspended
+        pages are being cleared.
+        * UIProcess/WebProcessCache.h:
+        (WebKit::WebProcessCache::disabled const): Added.
+        (WebKit::WebProcessCache::setDisabled): Added.
+        * UIProcess/WebProcessPool.cpp:
+        (WebKit::WebProcessPool::handleMemoryPressureWarning):
+        (WebKit::WebProcessPool::clearSuspendedPages): Added.
+        * UIProcess/WebProcessPool.h:
+        * UIProcess/WebsiteData/WebsiteDataStore.cpp:
+        (WebKit::WebsiteDataStore::removeData):
+
 2019-02-21  Alex Christensen  <[email protected]>
 
         Clicking "Go Back" on a safe browsing warning before a WKWebView has loaded any page should request to close the WKWebView

Source/WebKit/UIProcess/API/Cocoa/WKProcessPool.mm

@@ -514,6 +514,11 @@ - (NSUInteger)_maximumSuspendedPageCount
     return _processPool->maxSuspendedPageCount();
 }
 
+- (NSUInteger)_processCacheCapacity
+{
+    return _processPool->webProcessCache().capacity();
+}
+
 - (size_t)_serviceWorkerProcessCount
 {
 #if ENABLE(SERVICE_WORKER)

Source/WebKit/UIProcess/API/Cocoa/WKProcessPoolPrivate.h

@@ -103,6 +103,7 @@
 - (void)_makeNextWebProcessLaunchFailForTesting WK_API_AVAILABLE(macosx(10.14), ios(12.0));
 - (void)_makeNextNetworkProcessLaunchFailForTesting WK_API_AVAILABLE(macosx(10.14), ios(12.0));
 - (NSUInteger)_maximumSuspendedPageCount WK_API_AVAILABLE(macosx(WK_MAC_TBA), ios(WK_IOS_TBA));
+- (NSUInteger)_processCacheCapacity WK_API_AVAILABLE(macosx(WK_MAC_TBA), ios(WK_IOS_TBA));
 
 // Test only. Returns web processes running web pages (does not include web processes running service workers)
 - (size_t)_webPageContentProcessCount WK_API_AVAILABLE(macosx(10.13.4), ios(11.3));

Source/WebKit/UIProcess/WebProcessCache.cpp

@@ -51,7 +51,7 @@ bool WebProcessCache::addProcessIfPossible(const String& registrableDomain, Ref<
     ASSERT(!process->provisionalPageCount());
     ASSERT(!process->processPool().hasSuspendedPageFor(process));
 
-    if (!capacity())
+    if (!capacity() || m_isDisabled)
         return false;
 
     if (MemoryPressureHandler::singleton().isUnderMemoryPressure()) {
@@ -85,7 +85,7 @@ bool WebProcessCache::addProcess(const String& registrableDomain, Ref<WebProcess
     ASSERT(!process->provisionalPageCount());
     ASSERT(!process->processPool().hasSuspendedPageFor(process));
 
-    if (!capacity())
+    if (!capacity() || m_isDisabled)
         return false;
 
     if (MemoryPressureHandler::singleton().isUnderMemoryPressure()) {

Source/WebKit/UIProcess/WebProcessCache.h

@@ -49,6 +49,8 @@ class WebProcessCache {
 
     unsigned size() const { return m_processesPerRegistrableDomain.size(); }
 
+    void setIsDisabled(bool isDisabled) { m_isDisabled = isDisabled; }
+
     void clear();
     void setApplicationIsActive(bool);
 
@@ -61,6 +63,7 @@ class WebProcessCache {
     bool addProcess(const String& registrableDomain, Ref<WebProcessProxy>&&);
 
     unsigned m_capacity { 0 };
+    bool m_isDisabled { false };
 
     class CachedProcess {
         WTF_MAKE_FAST_ALLOCATED;

Source/WebKit/UIProcess/WebProcessPool.cpp

@@ -1340,7 +1340,7 @@ void WebProcessPool::handleMemoryPressureWarning(Critical)
         m_prewarmedProcess->shutDown();
     ASSERT(!m_prewarmedProcess);
 
-    m_suspendedPages.clear();
+    clearSuspendedPages();
 }
 
 #if ENABLE(NETSCAPE_PLUGIN_API)
@@ -2352,6 +2352,11 @@ bool WebProcessPool::hasSuspendedPageFor(WebProcessProxy& process, WebPageProxy*
     }) != m_suspendedPages.end();
 }
 
+void WebProcessPool::clearSuspendedPages()
+{
+    m_suspendedPages.clear();
+}
+
 void WebProcessPool::addMockMediaDevice(const MockMediaDevice& device)
 {
 #if ENABLE(MEDIA_STREAM)

Source/WebKit/UIProcess/WebProcessPool.h

@@ -468,6 +468,7 @@ class WebProcessPool final : public API::ObjectImpl<API::Object::Type::ProcessPo
     bool hasSuspendedPageFor(WebProcessProxy&, WebPageProxy* = nullptr) const;
     unsigned maxSuspendedPageCount() const { return m_maxSuspendedPageCount; }
     RefPtr<WebProcessProxy> findReusableSuspendedPageProcess(const String&, WebPageProxy&);
+    void clearSuspendedPages();
 
     void didReachGoodTimeToPrewarm();
 

Source/WebKit/UIProcess/WebsiteData/WebsiteDataStore.cpp

@@ -36,6 +36,7 @@
 #include "ShouldGrandfatherStatistics.h"
 #include "StorageAccessStatus.h"
 #include "StorageManager.h"
+#include "WebProcessCache.h"
 #include "WebProcessMessages.h"
 #include "WebProcessPool.h"
 #include "WebResourceLoadStatisticsStore.h"
@@ -778,6 +779,16 @@ void WebsiteDataStore::removeData(OptionSet<WebsiteDataType> dataTypes, WallTime
 
     auto webProcessAccessType = computeWebProcessAccessTypeForDataRemoval(dataTypes, !isPersistent());
     if (webProcessAccessType != ProcessAccessType::None) {
+        for (auto& processPool : processPools()) {
+            processPool->webProcessCache().setIsDisabled(true);
+            processPool->clearSuspendedPages();
+            // FIXME: We need to delay the clearing of the process cache because ~SuspendedPageProxy() calls maybeShutDown asynchronously.
+            RunLoop::main().dispatch([pool = makeRef(*processPool)] {
+                pool->webProcessCache().clear();
+                pool->webProcessCache().setIsDisabled(false);
+            });
+        }
+
         for (auto& process : processes()) {
             switch (webProcessAccessType) {
             case ProcessAccessType::OnlyIfLaunched:

Tools/ChangeLog

@@ -1,3 +1,15 @@
+2019-02-21  Ryosuke Niwa  <[email protected]>
+
+        Discard cached processes when clearing website data store
+        https://bugs.webkit.org/show_bug.cgi?id=194894
+
+        Reviewed by Chris Dumez.
+
+        Added a test case.
+
+        * TestWebKitAPI/Tests/WebKitCocoa/ProcessSwapOnNavigation.mm:
+        (TestWebKitAPI.ProcessSwap.NumberOfCachedProcesses): Added.
+
 2019-02-21  Alex Christensen  <[email protected]>
 
         Clicking "Go Back" on a safe browsing warning before a WKWebView has loaded any page should request to close the WKWebView

Tools/TestWebKitAPI/Tests/WebKitCocoa/ProcessSwapOnNavigation.mm

@@ -52,6 +52,7 @@
 #import <wtf/HashSet.h>
 #import <wtf/RetainPtr.h>
 #import <wtf/Vector.h>
+#import <wtf/text/StringConcatenateNumbers.h>
 #import <wtf/text/StringHash.h>
 #import <wtf/text/WTFString.h>
 
@@ -3058,6 +3059,62 @@ function loaded() {
     EXPECT_TRUE([processPool _hasPrewarmedWebProcess]);
 }
 
+TEST(ProcessSwap, NumberOfCachedProcesses)
+{
+    auto processPoolConfiguration = adoptNS([[_WKProcessPoolConfiguration alloc] init]);
+    processPoolConfiguration.get().processSwapsOnNavigation = YES;
+    processPoolConfiguration.get().usesWebProcessCache = YES;
+    processPoolConfiguration.get().prewarmsProcessesAutomatically = NO;
+    auto processPool = adoptNS([[WKProcessPool alloc] _initWithConfiguration:processPoolConfiguration.get()]);
+
+    EXPECT_GT([processPool _maximumSuspendedPageCount], 0u);
+    EXPECT_GT([processPool _processCacheCapacity], 0u);
+
+    auto webViewConfiguration = adoptNS([[WKWebViewConfiguration alloc] init]);
+    [webViewConfiguration setProcessPool:processPool.get()];
+    auto handler = adoptNS([[PSONScheme alloc] init]);
+
+    const unsigned maxSuspendedPageCount = [processPool _maximumSuspendedPageCount];
+    for (unsigned i = 0; i < maxSuspendedPageCount + 2; i++)
+        [handler addMappingFromURLString:makeString("pson://www.domain-", i, ".com") toData:pageCache1Bytes];
+    [webViewConfiguration setURLSchemeHandler:handler.get() forURLScheme:@"PSON"];
+
+    auto webView = adoptNS([[WKWebView alloc] initWithFrame:NSMakeRect(0, 0, 800, 600) configuration:webViewConfiguration.get()]);
+    auto delegate = adoptNS([[PSONNavigationDelegate alloc] init]);
+    [webView setNavigationDelegate:delegate.get()];
+
+    for (unsigned i = 0; i < maxSuspendedPageCount + 1; i++) {
+        NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:makeString("pson://www.domain-", i, ".com")]];
+        [webView loadRequest:request];
+        TestWebKitAPI::Util::run(&done);
+        done = false;
+
+        EXPECT_EQ(i + 1, [processPool _webProcessCount]);
+        EXPECT_EQ(i + 1, [processPool _webProcessCountIgnoringPrewarmedAndCached]);
+        EXPECT_FALSE([processPool _hasPrewarmedWebProcess]);
+    }
+
+    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:makeString("pson://www.domain-", maxSuspendedPageCount + 1, ".com")]];
+    [webView loadRequest:request];
+    TestWebKitAPI::Util::run(&done);
+    done = false;
+
+    EXPECT_EQ(maxSuspendedPageCount + 2, [processPool _webProcessCount]);
+    EXPECT_EQ(maxSuspendedPageCount + 1, [processPool _webProcessCountIgnoringPrewarmedAndCached]);
+    EXPECT_FALSE([processPool _hasPrewarmedWebProcess]);
+
+    static bool readyToContinue = false;
+    [[WKWebsiteDataStore defaultDataStore] removeDataOfTypes:[WKWebsiteDataStore _allWebsiteDataTypesIncludingPrivate] modifiedSince:[NSDate distantPast] completionHandler:^() {
+        readyToContinue = true;
+    }];
+    TestWebKitAPI::Util::run(&readyToContinue);
+
+    EXPECT_EQ(1u, [processPool _webProcessCount]);
+    EXPECT_EQ(1u, [processPool _webProcessCountIgnoringPrewarmedAndCached]);
+    EXPECT_FALSE([processPool _hasPrewarmedWebProcess]);
+
+}
+
 static const char* visibilityBytes = R"PSONRESOURCE(
 <script>
 window.addEventListener('pageshow', function(event) {