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List: kde-panel-devel
Subject: Re: Review Request 121710: Avoid risk of starting two kscreen_launchers at the same having race cond
From: Lukáš Tinkl <lukas () kde ! org>
Date: 2014-12-29 1:55:49
Message-ID: 20141229015549.18351.16360 () probe ! kde ! org
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Unfortunataly it doesn't fix it here, plasmashell starts with a blank screen. \
kquitapp5 plasmashell && plasmashell brings it back
- Lukáš Tinkl
On Pro. 28, 2014, 11:33 dop., David Edmundson wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/121710/
> -----------------------------------------------------------
>
> (Updated Pro. 28, 2014, 11:33 dop.)
>
>
> Review request for Plasma, Solid and Daniel Vrátil.
>
>
> Repository: libkscreen
>
>
> Description
> -------
>
> Avoid risk of starting two kscreen_launchers at the same having a race condition.
>
> There were three possible bugs:
> CheckIsAlreadyRunning tried to register a service and check if it worked.
> This could clash with another process checking at the same time. Causing them both \
> to fail saying another is running Similarly, a daemon doing actual registering \
> could clash with another daemon just checking if the name is free, and then it \
> would fail saying we can't init()
> There was also a risk that two launchers pass the check that nothing is running, \
> then both try to activate a session. DBus server handles this fine and one will \
> gracefully fail. Without this patch the second launcher would just die without \
> returning the path of the service that was activated causing the relevant app to do \
> nothing.
>
> --
>
> IMHO, you'd be better off having a fixed service name and using DBus activation for \
> exactly these reasons. You could put the different backends at different object \
> paths, and have a method on the root object that says which object path to use \
> rather than using the stdout of a launcher. That's a discussion for another day \
> though.
>
> Diffs
> -----
>
> src/backendlauncher/backendloader.cpp e7da8cd
> src/backendlauncher/main.cpp f8bf323
>
> Diff: https://git.reviewboard.kde.org/r/121710/diff/
>
>
> Testing
> -------
>
> Send it to bshah. Plasmashell started for him. Previously it didn't.
>
>
> Thanks,
>
> David Edmundson
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/121710/">https://git.reviewboard.kde.org/r/121710/</a>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">Unfortunataly it doesn't fix it here, plasmashell starts with a blank \
screen. kquitapp5 plasmashell && plasmashell brings it back</p></pre> <br />
<p>- Lukáš Tinkl</p>
<br />
<p>On prosinec 28th, 2014, 11:33 dop. CET, David Edmundson wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="12" style="border: \
1px #888a85 solid; border-radius: 6px; -moz-border-radius: 6px; \
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<div>Review request for Plasma, Solid and Daniel Vrátil.</div>
<div>By David Edmundson.</div>
<p style="color: grey;"><i>Updated Pro. 28, 2014, 11:33 dop.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
libkscreen
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Avoid risk of starting two kscreen_launchers at the \
same having a race condition.</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">There were three \
possible bugs: CheckIsAlreadyRunning tried to register a service and check if it \
worked. This could clash with another process checking at the same time. Causing them \
both to fail saying another is running Similarly, a daemon doing actual registering \
could clash with another daemon just checking if the name is free, and then it would \
fail saying we can't init()</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">There was also a risk that two \
launchers pass the check that nothing is running, then both try to activate a \
session. DBus server handles this fine and one will gracefully fail. Without this \
patch the second launcher would just die without returning the path of the service \
that was activated causing the relevant app to do nothing.</p> <p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">--</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">IMHO, you'd be better off having a fixed service name \
and using DBus activation for exactly these reasons. You could put the different \
backends at different object paths, and have a method on the root object that says \
which object path to use rather than using the stdout of a launcher. That's a \
discussion for another day though.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Send it to bshah. Plasmashell started for him. \
Previously it didn't.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>src/backendlauncher/backendloader.cpp <span style="color: \
grey">(e7da8cd)</span></li>
<li>src/backendlauncher/main.cpp <span style="color: grey">(f8bf323)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/121710/diff/" style="margin-left: \
3em;">View Diff</a></p>
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