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List: konsole-devel
Subject: Re: Review Request 130117: Fix detection of EOF
From: Martin Tobias Holmedahl Sandsmark <martin.sandsmark () kde ! org>
Date: 2017-06-03 18:22:11
Message-ID: 20170603182211.3028.85885 () mimi ! kde ! org
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> On May 8, 2017, 7:40 a.m., Oswald Buddenhagen wrote:
> > this looks familiar ... https://phabricator.kde.org/D4975
> >
> > so assuming the condition is valid, this requires an _extensive_ comment.
> > also, shouldn't this just be unified with the solaris code path?
>
> Martin Tobias Holmedahl Sandsmark wrote:
> No, Solaris has a very different behavior that is described by the already existing \
> comment (needing to "drain" the empty bytes with read(..., 0); etc.). It won't work \
> on Linux.
> What stuff do you want in the comment? I described how detecting an EOF is supposed \
> to be done (by actually trying to read).
> Oswald Buddenhagen wrote:
> the part i find interesting is the explanation of the confirmed legit situations \
> where this can occur. judging by the phab diff, there is a change of behavior in \
> the kernel involved. otoh, the bugzilla entry suggests that there is a behavior \
> change in kpty, which doesn't ring a bell in to me. i want that cleared up, because \
> it _smells_.
> Peter Wu wrote:
> I agree with Oswald, while the fix might hide the issue, the real question is why \
> it happens.
> My patch tried to explain why it possibly happened, but it was still guesswork and \
> not fully confirmed. This patch does not even explain why the assumption should be \
> removed.
> If you have time, please try to reach the kernel developers (ideally with a minimal \
> testcase, one which I failed to create), maybe they have an idea.
I don't have time to spend on this, and to me just getting konsole to work is more \
important than finding out when the kernel behavior changed. To me the old way to \
check for EOF seems like something that worked by accident, this patch is the correct \
way I would implement it with the way the kernel works now (e. g. look at \
https://github.com/torvalds/linux/blob/v4.11/drivers/tty/n_tty.c#L2179-L2182).
- Martin Tobias Holmedahl
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/130117/#review103203
-----------------------------------------------------------
On May 6, 2017, 6:09 p.m., Martin Tobias Holmedahl Sandsmark wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/130117/
> -----------------------------------------------------------
>
> (Updated May 6, 2017, 6:09 p.m.)
>
>
> Review request for Konsole, Kurt Hindenburg, Oswald Buddenhagen, and Peter Wu.
>
>
> Bugs: 372991
> https://bugs.kde.org/show_bug.cgi?id=372991
>
>
> Repository: kpty
>
>
> Description
> -------
>
> Don't just assume that 0 bytes read means EOF.
>
>
> Diffs
> -----
>
> src/kptydevice.cpp 22233a5
>
> Diff: https://git.reviewboard.kde.org/r/130117/diff/
>
>
> Testing
> -------
>
> Fixes the konsole issue from https://phabricator.kde.org/D4975 and \
> https://bugs.kde.org/show_bug.cgi?id=372991 and the autotest works.
>
> Thanks,
>
> Martin Tobias Holmedahl Sandsmark
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/130117/">https://git.reviewboard.kde.org/r/130117/</a>
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<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On May 8th, 2017, 7:40 a.m. UTC, <b>Oswald \
Buddenhagen</b> wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px \
solid #d0d0d0; padding-left: 10px;"> <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;">this looks familiar ... \
https://phabricator.kde.org/D4975</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">so assuming the \
condition is valid, this requires an <em style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: normal;">extensive</em> comment. \
also, shouldn't this just be unified with the solaris code path?</p></pre> \
</blockquote>
<p>On May 8th, 2017, 11:03 a.m. UTC, <b>Martin Tobias Holmedahl Sandsmark</b> \
wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; \
padding-left: 10px;"> <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;">No, Solaris has a very different behavior that is described by the already \
existing comment (needing to "drain" the empty bytes with read(..., 0); etc.). It \
won't work on Linux.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">What stuff do you want in the comment? \
I described how detecting an EOF is supposed to be done (by actually trying to \
read).</p></pre> </blockquote>
<p>On May 8th, 2017, 8:02 p.m. UTC, <b>Oswald Buddenhagen</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <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;">the \
part i find interesting is the explanation of the confirmed legit situations where \
this can occur. judging by the phab diff, there is a change of behavior in the kernel \
involved. otoh, the bugzilla entry suggests that there is a behavior change in kpty, \
which doesn't ring a bell in to me. i want that cleared up, because it <em \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">smells</em>.</p></pre> </blockquote>
<p>On May 8th, 2017, 8:33 p.m. UTC, <b>Peter Wu</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <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;">I \
agree with Oswald, while the fix might hide the issue, the real question is why it \
happens.</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">My patch tried to explain why it possibly happened, \
but it was still guesswork and not fully confirmed. This patch does not even explain \
why the assumption should be removed.</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">If you have time, \
please try to reach the kernel developers (ideally with a minimal testcase, one which \
I failed to create), maybe they have an idea.</p></pre> </blockquote>
</blockquote>
<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;">I \
don't have time to spend on this, and to me just getting konsole to work is more \
important than finding out when the kernel behavior changed. To me the old way to \
check for EOF seems like something that worked by accident, this patch is the correct \
way I would implement it with the way the kernel works now (e. g. look at \
https://github.com/torvalds/linux/blob/v4.11/drivers/tty/n_tty.c#L2179-L2182).</p></pre>
<br />
<p>- Martin Tobias Holmedahl</p>
<br />
<p>On May 6th, 2017, 6:09 p.m. UTC, Martin Tobias Holmedahl Sandsmark 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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<td>
<div>Review request for Konsole, Kurt Hindenburg, Oswald Buddenhagen, and Peter \
Wu.</div> <div>By Martin Tobias Holmedahl Sandsmark.</div>
<p style="color: grey;"><i>Updated May 6, 2017, 6:09 p.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="https://bugs.kde.org/show_bug.cgi?id=372991">372991</a>
</div>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
kpty
</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;">Don't just assume that 0 bytes read means \
EOF.</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;">Fixes the konsole issue from \
https://phabricator.kde.org/D4975 and https://bugs.kde.org/show_bug.cgi?id=372991 and \
the autotest works.</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/kptydevice.cpp <span style="color: grey">(22233a5)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/130117/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
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