Bug 52569 – [Qt][WK2] Crash due to double destruction of QSharedMemory

• Component: WebKit2
• Status: RESOLVED FIXED

[Balazs Kelemen]

Some layout tests are crashing because of a bug associated with the CleanupHandler.
For example fast/forms/form-associated-element-crash.html produce the following backtrace:
Program received signal SIGSEGV, Segmentation fault.
0x080c9f50 in ?? ()
(gdb) bt 10
#0  0x080c9f50 in ?? ()
#1  0xb70e3925 in WTF::RefCounted<WebKit::SharedMemory>::deref (this=0x80ef9e8) at ../../../../Source/JavaScriptCore/wtf/RefCounted.h:139
#2  0xb70e3961 in WTF::derefIfNotNull<WebKit::SharedMemory> (ptr=0x80ef9e8) at ../../../../Source/JavaScriptCore/wtf/PassRefPtr.h:59
#3  0xb70e39ad in WTF::RefPtr<WebKit::SharedMemory>::~RefPtr (this=0x80ccee8, __in_chrg=<value optimized out>)
    at ../../../../Source/JavaScriptCore/wtf/RefPtr.h:57
#4  0xb70f6097 in WebKit::VisitedLinkTable::~VisitedLinkTable (this=0x80ccee8, __in_chrg=<value optimized out>)
    at ../../../../Source/WebKit2/Shared/VisitedLinkTable.cpp:42
#5  0xb714a50a in WebKit::VisitedLinkProvider::~VisitedLinkProvider (this=0x80cced8, __in_chrg=<value optimized out>)
    at ../../../../Source/WebKit2/UIProcess/VisitedLinkProvider.h:40
#6  0xb7140dd5 in WebKit::WebContext::~WebContext (this=0x80cce70, __in_chrg=<value optimized out>)
    at ../../../../Source/WebKit2/UIProcess/WebContext.cpp:120
...

This is the symptom of deleting the QSharedMemory twice.
The following happens in this scenario in time oriented order:
1. QApplication stopping =>
2. CleanupHandler deletes the QSharedMemory in the slot connected to QApplication::aboutToQuit
3. Destructor of SharedMemory is reached through the destruction of the TestController.

The code that was preventing from this behavior was removed by http://trac.webkit.org/changeset/74967 because of my wrong assumption that
it is not needed anymore.

[Balazs Kelemen]

Created attachment 79158 [details]
Patch

[Andreas Kling]

Comment on attachment 79158 [details]
Patch

r=me

[Balazs Kelemen]

Comment on attachment 79158 [details]
Patch

Clearing flags on attachment: 79158

Committed r75935: <http://trac.webkit.org/changeset/75935>

[Balazs Kelemen]

All reviewed patches have been landed.  Closing bug.