From: bugzilla-daemon@bugzilla.kernel.org
To: linux-ext4@vger.kernel.org
Subject: [Bug 14354] Bad corruption with 2.6.32-rc1 and upwards
Date: Fri, 30 Oct 2009 18:05:36 GMT [thread overview]
Message-ID: <200910301805.n9UI5aFH016683@demeter.kernel.org> (raw)
In-Reply-To: <bug-14354-13602@http.bugzilla.kernel.org/>
http://bugzilla.kernel.org/show_bug.cgi?id=14354
--- Comment #157 from Linus Torvalds <torvalds@linux-foundation.org> 2009-10-30 18:05:28 ---
On Fri, 30 Oct 2009, bugzilla-daemon@bugzilla.kernel.org wrote:
>
> Well I've been doing bisects but I'm getting skeptical of the results;
> either my testcase isn't reliable enough or all the merges are confusing
> git-bisect (?) Anyway it keeps ending up on nonsensical commits.
Merges don't confuse git-bisect (lots of merges may make bisection
slightly less _efficient_, though, because it can be impossible to find
commits that are nicely "in the middle"), but the way bisection works,
even a _single_ wrong "git bisect good/bad" statement can - and will -
make bisection results go off totally in the weeds.
Bisection is designed to be efficient, which is absolutely wonderful when
you have a 100% unambiguous bug that needs to be found in 10,000 commits.
It's what gives us that nice log2() behavior.
But the downside of that efficiency is the same as the downside of any
very efficient data compression with no checksum: there is absolutely zero
redundancy. So then if even just a single bit of information (in this case
the "good/bad" info) is wrong, the end result will not just be wrong - it
will be _disastrously_ wrong, and you won't even be anywhere _close_ to
the correct end result.
[ In fact, the way bisection works, if you give a single incorrect
bisection point, the end result will usually be close to the commit you
incorrectly marked, rather than the actual buggy commit you searched
for.
That _can_ be used as a hint when you're unsure - when getting a clearly
bogus bisection result, you can look at the bisect log, and try to find
the first commit in the log that is close to the clearly bogus result,
and you might decide to re-test that commit more carefully. And then if,
on re-testing, it turns out that you had been wrong the first time, you
might be able to avoid re-doing the whole bisection thing, and instead
re-do the log up to the incorrect - and now fixed - entry, and continue
from there. ]
That said, if you end up being uncertain about the bisection points, and
can't give more than a "95% confidence", bisection will almost inevitably
fail. A bug that is timing-dependent can be almost impossible to bisect.
Even if you can reliably trigger it _eventually_, you may have to test so
long at each bisection point that bisection becomes practically useless.
Linus
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next prev parent reply other threads:[~2009-10-30 18:05 UTC|newest]
Thread overview: 218+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-09 15:42 [Bug 14354] New: Bad corruption with 2.6.32-rc1 and upwards bugzilla-daemon
2009-10-09 15:51 ` [Bug 14354] " bugzilla-daemon
2009-10-09 16:06 ` bugzilla-daemon
2009-10-09 16:44 ` bugzilla-daemon
2009-10-09 16:50 ` bugzilla-daemon
2009-10-09 22:35 ` bugzilla-daemon
2009-10-10 7:32 ` bugzilla-daemon
2009-10-10 16:48 ` bugzilla-daemon
2009-10-10 16:50 ` bugzilla-daemon
2009-10-10 17:00 ` bugzilla-daemon
2009-10-10 17:04 ` bugzilla-daemon
2009-10-10 19:54 ` bugzilla-daemon
2009-10-11 1:26 ` bugzilla-daemon
2009-10-11 2:03 ` bugzilla-daemon
2009-10-11 12:31 ` bugzilla-daemon
2009-10-11 19:07 ` bugzilla-daemon
2009-10-11 21:45 ` bugzilla-daemon
2009-10-11 23:01 ` bugzilla-daemon
2009-10-12 0:02 ` bugzilla-daemon
2009-10-12 2:18 ` bugzilla-daemon
2009-10-12 2:24 ` bugzilla-daemon
2009-10-12 7:54 ` bugzilla-daemon
2009-10-12 7:56 ` bugzilla-daemon
2009-10-12 7:57 ` bugzilla-daemon
2009-10-12 15:24 ` bugzilla-daemon
2009-10-12 15:27 ` [Bug 14354] New: " Aneesh Kumar K.V
2009-10-12 15:27 ` [Bug 14354] " bugzilla-daemon
2009-10-12 18:15 ` bugzilla-daemon
2009-10-12 18:29 ` bugzilla-daemon
2009-10-12 21:41 ` bugzilla-daemon
2009-10-12 21:50 ` bugzilla-daemon
2009-10-13 0:18 ` bugzilla-daemon
2009-10-13 8:00 ` bugzilla-daemon
2009-10-13 8:02 ` bugzilla-daemon
2009-10-13 8:47 ` bugzilla-daemon
2009-10-13 13:16 ` bugzilla-daemon
2009-10-13 14:50 ` bugzilla-daemon
2009-10-13 15:12 ` bugzilla-daemon
2009-10-13 20:17 ` bugzilla-daemon
2009-10-13 20:28 ` bugzilla-daemon
2009-10-13 20:55 ` bugzilla-daemon
2009-10-13 21:10 ` bugzilla-daemon
2009-10-13 22:02 ` bugzilla-daemon
2009-10-14 0:45 ` bugzilla-daemon
2009-10-14 0:48 ` bugzilla-daemon
2009-10-14 2:31 ` bugzilla-daemon
2009-10-14 3:17 ` bugzilla-daemon
2009-10-14 3:26 ` bugzilla-daemon
2009-10-14 9:31 ` bugzilla-daemon
2009-10-14 13:21 ` bugzilla-daemon
2009-10-14 13:36 ` bugzilla-daemon
2009-10-14 22:08 ` bugzilla-daemon
2009-10-14 22:09 ` bugzilla-daemon
2009-10-14 22:11 ` bugzilla-daemon
2009-10-15 4:24 ` bugzilla-daemon
2009-10-15 7:11 ` bugzilla-daemon
2009-10-15 15:07 ` bugzilla-daemon
2009-10-15 17:58 ` bugzilla-daemon
2009-10-15 18:30 ` bugzilla-daemon
2009-10-15 19:10 ` bugzilla-daemon
2009-10-15 23:40 ` bugzilla-daemon
2009-10-16 9:16 ` bugzilla-daemon
2009-10-16 10:48 ` bugzilla-daemon
2009-10-16 14:13 ` bugzilla-daemon
2009-10-16 14:41 ` bugzilla-daemon
2009-10-16 15:27 ` bugzilla-daemon
2009-10-16 19:14 ` bugzilla-daemon
2009-10-16 19:39 ` bugzilla-daemon
2009-10-16 20:05 ` bugzilla-daemon
2009-10-16 20:07 ` bugzilla-daemon
2009-10-16 22:24 ` bugzilla-daemon
2009-10-16 23:02 ` bugzilla-daemon
2009-10-17 2:27 ` bugzilla-daemon
2009-10-17 6:01 ` bugzilla-daemon
2009-10-17 6:03 ` bugzilla-daemon
2009-10-17 6:12 ` bugzilla-daemon
2009-10-17 6:38 ` bugzilla-daemon
2009-10-17 6:38 ` bugzilla-daemon
2009-10-17 6:43 ` bugzilla-daemon
2009-10-17 8:18 ` bugzilla-daemon
2009-10-17 10:51 ` bugzilla-daemon
2009-10-17 11:37 ` bugzilla-daemon
2009-10-17 14:37 ` bugzilla-daemon
2009-10-17 14:40 ` bugzilla-daemon
2009-10-17 15:23 ` bugzilla-daemon
2009-10-17 17:46 ` bugzilla-daemon
2009-10-17 19:57 ` bugzilla-daemon
2009-10-17 20:54 ` bugzilla-daemon
2009-10-17 20:59 ` bugzilla-daemon
2009-10-18 0:02 ` bugzilla-daemon
2009-10-18 0:03 ` bugzilla-daemon
2009-10-18 0:04 ` bugzilla-daemon
2009-10-18 0:04 ` bugzilla-daemon
2009-10-18 0:05 ` bugzilla-daemon
2009-10-18 0:05 ` bugzilla-daemon
2009-10-18 0:07 ` bugzilla-daemon
2009-10-18 0:07 ` bugzilla-daemon
2009-10-18 0:07 ` bugzilla-daemon
2009-10-18 7:44 ` bugzilla-daemon
2009-10-18 10:06 ` bugzilla-daemon
2009-10-18 11:23 ` bugzilla-daemon
2009-10-18 11:25 ` bugzilla-daemon
2009-10-18 11:57 ` bugzilla-daemon
2009-10-19 21:07 ` bugzilla-daemon
2009-10-19 21:08 ` bugzilla-daemon
2009-10-20 17:28 ` bugzilla-daemon
2009-10-20 20:21 ` bugzilla-daemon
2009-10-21 0:53 ` bugzilla-daemon
2009-10-21 0:57 ` bugzilla-daemon
2009-10-21 5:55 ` bugzilla-daemon
2009-10-21 9:05 ` bugzilla-daemon
2009-10-21 9:06 ` bugzilla-daemon
2009-10-22 18:43 ` bugzilla-daemon
2009-10-22 19:06 ` bugzilla-daemon
2009-10-22 19:22 ` bugzilla-daemon
2009-10-22 19:29 ` bugzilla-daemon
2009-10-22 19:37 ` bugzilla-daemon
2009-10-22 21:58 ` bugzilla-daemon
2009-10-22 22:24 ` bugzilla-daemon
2009-10-23 4:30 ` bugzilla-daemon
2009-10-23 7:45 ` bugzilla-daemon
2009-10-24 17:04 ` bugzilla-daemon
2009-10-24 17:05 ` bugzilla-daemon
2009-10-25 8:58 ` bugzilla-daemon
2009-10-25 13:59 ` bugzilla-daemon
2009-10-25 14:01 ` bugzilla-daemon
2009-10-25 19:04 ` bugzilla-daemon
2009-10-26 13:46 ` bugzilla-daemon
2009-10-26 15:42 ` bugzilla-daemon
2009-10-26 16:17 ` bugzilla-daemon
2009-10-26 19:13 ` bugzilla-daemon
2009-10-26 21:46 ` bugzilla-daemon
2009-10-26 22:40 ` bugzilla-daemon
2009-10-27 6:54 ` Aneesh Kumar K.V
2009-10-27 6:39 ` bugzilla-daemon
2009-10-27 10:00 ` bugzilla-daemon
2009-10-27 10:38 ` bugzilla-daemon
2009-10-27 11:03 ` Aneesh Kumar K.V
2009-10-27 10:48 ` bugzilla-daemon
2009-10-27 11:47 ` bugzilla-daemon
2009-10-27 12:41 ` bugzilla-daemon
2009-10-27 13:02 ` bugzilla-daemon
2009-10-27 18:50 ` bugzilla-daemon
2009-10-27 19:00 ` bugzilla-daemon
2009-10-27 20:00 ` bugzilla-daemon
2009-10-27 20:31 ` bugzilla-daemon
2009-10-27 20:37 ` bugzilla-daemon
2009-10-27 21:23 ` bugzilla-daemon
2009-10-27 21:42 ` bugzilla-daemon
2009-10-27 22:04 ` bugzilla-daemon
2009-10-27 23:38 ` bugzilla-daemon
2009-10-28 6:44 ` bugzilla-daemon
2009-10-28 7:20 ` bugzilla-daemon
2009-10-29 16:23 ` bugzilla-daemon
2009-10-29 16:47 ` bugzilla-daemon
2009-10-29 17:34 ` bugzilla-daemon
2009-10-29 20:11 ` bugzilla-daemon
2009-10-29 21:25 ` bugzilla-daemon
2009-10-29 21:39 ` bugzilla-daemon
2009-10-29 21:42 ` bugzilla-daemon
2009-10-29 21:52 ` bugzilla-daemon
2009-10-29 21:55 ` bugzilla-daemon
2009-10-29 22:20 ` bugzilla-daemon
2009-10-29 22:23 ` bugzilla-daemon
2009-10-30 8:16 ` bugzilla-daemon
2009-10-30 8:22 ` bugzilla-daemon
2009-10-30 10:26 ` bugzilla-daemon
2009-10-30 10:42 ` bugzilla-daemon
2009-10-30 13:54 ` bugzilla-daemon
2009-10-30 16:27 ` bugzilla-daemon
2009-10-30 18:05 ` bugzilla-daemon [this message]
2009-10-30 19:17 ` bugzilla-daemon
2009-10-30 19:22 ` bugzilla-daemon
2009-10-30 19:56 ` bugzilla-daemon
2009-10-31 9:15 ` bugzilla-daemon
2009-10-31 15:26 ` bugzilla-daemon
2009-10-31 16:16 ` bugzilla-daemon
2009-10-31 19:15 ` bugzilla-daemon
2009-10-31 19:56 ` bugzilla-daemon
2009-11-02 4:07 ` bugzilla-daemon
2009-11-02 17:05 ` bugzilla-daemon
2009-11-02 23:11 ` bugzilla-daemon
2009-11-03 1:07 ` bugzilla-daemon
2009-11-03 9:33 ` bugzilla-daemon
2009-11-03 13:37 ` bugzilla-daemon
2009-11-03 13:43 ` bugzilla-daemon
2009-11-03 13:58 ` bugzilla-daemon
2009-11-03 14:32 ` bugzilla-daemon
2009-11-03 23:39 ` bugzilla-daemon
2009-11-03 23:43 ` bugzilla-daemon
2009-11-04 3:33 ` bugzilla-daemon
2009-11-06 20:49 ` bugzilla-daemon
2009-11-06 22:07 ` bugzilla-daemon
2009-11-08 18:12 ` Christoph Hellwig
2009-11-08 19:12 ` Theodore Tso
2009-11-06 22:15 ` bugzilla-daemon
2009-11-06 22:26 ` bugzilla-daemon
2009-11-08 18:12 ` bugzilla-daemon
2009-11-08 19:12 ` bugzilla-daemon
2009-11-08 21:05 ` bugzilla-daemon
2009-11-08 21:12 ` Theodore Tso
2009-11-08 21:12 ` bugzilla-daemon
2009-11-09 14:54 ` bugzilla-daemon
2009-11-16 22:30 ` bugzilla-daemon
2009-11-16 22:30 ` bugzilla-daemon
2009-11-17 22:20 ` bugzilla-daemon
2009-11-17 22:21 ` bugzilla-daemon
2009-11-17 22:22 ` bugzilla-daemon
2009-10-11 22:07 2.6.32-rc4: Reported regressions from 2.6.31 Rafael J. Wysocki
2009-10-11 22:22 ` [Bug #14354] Bad corruption with 2.6.32-rc1 and upwards Rafael J. Wysocki
2009-10-26 18:45 2.6.32-rc5-git3: Reported regressions from 2.6.31 Rafael J. Wysocki
2009-10-26 18:55 ` [Bug #14354] Bad corruption with 2.6.32-rc1 and upwards Rafael J. Wysocki
2009-10-26 18:55 ` Rafael J. Wysocki
2009-11-16 22:33 2.6.32-rc7-git1: Reported regressions from 2.6.31 Rafael J. Wysocki
2009-11-16 22:37 ` [Bug #14354] Bad corruption with 2.6.32-rc1 and upwards Rafael J. Wysocki
2009-11-17 2:02 ` Theodore Tso
2009-11-17 2:02 ` Theodore Tso
2009-11-17 22:23 ` Rafael J. Wysocki
2009-11-17 22:23 ` Rafael J. Wysocki
2009-11-18 0:11 ` tytso
2009-11-18 0:11 ` tytso-3s7WtUTddSA
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