Re: ThreadSanitizer issue in RecentFileStatus()

[Roland Knall <rknall () gmail com>]

Would it make sense to either expand README.developer or add a
README.threading, detailing the new startup procedure? Otherwise we might
run into issues later where users might face those exact issues.

On Fri, Feb 2, 2018 at 7:33 PM, Gerald Combs <gerald () wireshark org> wrote:

> That's correct -- the main and RecentFileStatus threads could operate on
> the filename at the same time. I think the data race is harmless in this
> case, but it's easy enough to create a local copy of the filename. Fix
> inbound at https://code.wireshark.org/review/#/c/25572.
>
> On 2/2/18 8:08 AM, Jaap Keuter wrote:
> > Hi,
> >
> > Good question.
> > Just spitballing here, in what thread are the constructors running?
> > RecentFileStatus::filename_ is being set during construction, but is
> run() already called from the other thread?
> > Jaap
> >
> >
> > > On 2 Feb 2018, at 15:04, Stig Bjørlykke <stig () bjorlykke org> wrote:
> > >
> > > When running with ThreadSanitizer I constantly get this race condition
> > > report from a QString in RecentFileStatus.  Anyone else seen this?  I
> > > can't figure out the issue...
> > >
> > > ==================
> > > WARNING: ThreadSanitizer: data race (pid=41949)
> > >  Read of size 8 at 0x7b0c000c0dd0 by thread T18:
> > >  * #0 QString::QString(QString const&) qstring.h:906
> > > (Wireshark:x86_64+0x100039756)
> > >    #1 QString::QString(QString const&) qstring.h:907
> > > (Wireshark:x86_64+0x100038998)
> > >    #2 RecentFileStatus::run() recent_file_status.cpp:33
> > > (Wireshark:x86_64+0x1004ffbec)
> > >    #3 non-virtual thunk to RecentFileStatus::run()
> > > recent_file_status.cpp (Wireshark:x86_64+0x1004ffd2c)
> > >    #4 <null> <null>:8575680 (QtCore:x86_64+0x27b6d)
> > >
> > >  Previous write of size 8 at 0x7b0c000c0dd0 by main thread:
> > >  * #0 QString::QString(QString const&) qstring.h:906
> > > (Wireshark:x86_64+0x10003976d)
> > >    #1 QString::QString(QString const&) qstring.h:907
> > > (Wireshark:x86_64+0x100038998)
> > >    #2 RecentFileStatus::RecentFileStatus(QString, QObject*)
> > > recent_file_status.cpp:13 (Wireshark:x86_64+0x1004ff8b3)
> > >    #3 RecentFileStatus::RecentFileStatus(QString, QObject*)
> > > recent_file_status.cpp:14 (Wireshark:x86_64+0x1004ffac0)
> > >    #4 WiresharkApplication::refreshRecentCaptures()
> > > wireshark_application.cpp:256 (Wireshark:x86_64+0x10079a3b6)
> > >    #5 WiresharkApplication::qt_static_metacall(QObject*,
> > > QMetaObject::Call, int, void**)
> > > moc_wireshark_application_Debug.cpp:234 (Wireshark:x86_64+0x1000bbceb)
> > >    #6 QMetaObject::activate(QObject*, int, int, void**)
> > > <null>:8575680 (QtCore:x86_64+0x2194ba)
> > >    #7 main wireshark-qt.cpp:852 (Wireshark:x86_64+0x100037b0c)
> > >
> > >  Issue is caused by frames marked with "*".
> > >
> > >  Location is heap block of size 48 at 0x7b0c000c0db0 allocated by main
> thread:
> > >    #0 operator new(unsigned long) <null>:8575712
> > > (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x6ba8e)
> > >    #1 WiresharkApplication::refreshRecentCaptures()
> > > wireshark_application.cpp:256 (Wireshark:x86_64+0x10079a36a)
> > >    #2 WiresharkApplication::qt_static_metacall(QObject*,
> > > QMetaObject::Call, int, void**)
> > > moc_wireshark_application_Debug.cpp:234 (Wireshark:x86_64+0x1000bbceb)
> > >    #3 QMetaObject::activate(QObject*, int, int, void**)
> > > <null>:8575712 (QtCore:x86_64+0x2194ba)
> > >    #4 main wireshark-qt.cpp:852 (Wireshark:x86_64+0x100037b0c)
> > >
> > >  Thread T18 (tid=17501933, running) created by main thread at:
> > >    #0 pthread_create <null>:8575760
> > > (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x2a34d)
> > >    #1 QThread::start(QThread::Priority) <null>:8575760
> (QtCore:x86_64+0x2b5cb)
> > >    #2 main wireshark-qt.cpp:667 (Wireshark:x86_64+0x100036bcd)
> > >
> > > SUMMARY: ThreadSanitizer: data race qstring.h:906 in
> > > QString::QString(QString const&)
> > > ==================
> > >
> > >
> > > --
> > > Stig Bjørlykke
> >
> > ____________________________________________________________
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