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List:       kde-panel-devel
Subject:    D8673: Sanitize signal handling in ksmserver
From:       Jiří Paleček <noreply () phabricator ! kde ! org>
Date:       2017-11-06 0:25:17
Message-ID: 20171106002517.29577.0D6B75B74330C282 () phabricator ! kde ! org
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jpalecek edited the summary of this revision.

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D8673

To: jpalecek, #plasma
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, mart

[Attachment #3 (unknown)]

<table><tr><td style="">jpalecek edited the summary of this revision. <a \
href="https://phabricator.kde.org/transactions/detail/PHID-XACT-DREV-5s6fbumatj5ljah/" \
rel="noreferrer">(Show Details)</a> </td><a style="text-decoration: none; padding: \
4px 8px; margin: 0 8px 8px; float: right; color: #464C5C; font-weight: bold; \
border-radius: 3px; background-color: #F7F7F9; background-image: linear-gradient(to \
bottom,#fff,#f1f0f1); display: inline-block; border: 1px solid rgba(71,87,120,.2);" \
href="https://phabricator.kde.org/D8673" rel="noreferrer">View \
Revision</a></tr></table><br /><div><strong>CHANGES TO REVISION \
SUMMARY</strong><div><div style="white-space: pre-wrap; color: #74777D;">The TERM \
signal handling in ksmserver invokes functions which are not async-signal safe, like \
Qt functions and <span style="padding: 0 2px; color: #333333; background: rgba(251, \
175, 175, .7);">C++<br /> </span><span style="padding: 0 2px; color: #333333; \
background: rgba(151, 234, 151, .6);">C++ </span>destructors. Moreover, the signal \
handling can occur in other than the main thread, which leads to Qt complaining \
about<span style="padding: 0 2px; color: #333333; background: rgba(151, 234, 151, \
.6);"> </span> functions being invoked from the wrong thread. Such a crash can be \
seen in a report of [[ bug 384316 |https://bugs.kde.org/show_bug.cgi?id=384316 ]].<br \
/> <br />
To fix both of these issues, this change makes the signal handling use the self-pipe \
trick, which signals the need for termination to the main thread by writing to a \
special-purpose file descriptor. The main<span style="padding: 0 2px; color: #333333; \
background: rgba(251, 175, 175, .7);"><br /> </span><span style="padding: 0 2px; \
color: #333333; background: rgba(151, 234, 151, .6);"> </span>loop then takes care of \
the termination. This is mostly inspired by [[ \
http://doc.qt.io/qt-5/unix-signals.html ]].<br /> <br />
Note that `QApplication::quit` already does what we need when destroying<span \
style="padding: 0 2px; color: #333333; background: rgba(251, 175, 175, .7);"><br /> \
</span><span style="padding: 0 2px; color: #333333; background: rgba(151, 234, 151, \
.6);"> </span>the server, particularly deleting `the_server`/calling `cleanUp()`.<br \
/> <br />
BTW I noticed the code (here and in XIO error handler) makes quite<span \
style="padding: 0 2px; color: #333333; background: rgba(251, 175, 175, .7);"><br /> \
</span><span style="padding: 0 2px; color: #333333; background: rgba(151, 234, 151, \
.6);"> </span>sure the_server is zeroed. However, other code in ksmserver is not \
<span style="padding: 0 2px; color: #333333; background: rgba(251, 175, 175, \
.7);">so<br /> </span><span style="padding: 0 2px; color: #333333; background: \
rgba(151, 234, 151, .6);">so </span>keen on checking `the_server` is !0 when using \
it.</div></div></div><br /><div><strong>REPOSITORY</strong><div><div>R120 Plasma \
Workspace</div></div></div><br /><div><strong>REVISION DETAIL</strong><div><a \
href="https://phabricator.kde.org/D8673" \
rel="noreferrer">https://phabricator.kde.org/D8673</a></div></div><br \
/><div><strong>To: </strong>jpalecek, Plasma<br /><strong>Cc: </strong>plasma-devel, \
ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, \
mart<br /></div>



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