From: Matthew Wilcox <willy@infradead.org>
To: David Niklas <Hgntkwis@vfemail.net>
Cc: linux-doc@vger.kernel.org, corbet@lwn.net
Subject: Re: PROBLEM: Missing debug instructions when EIP is not present
Date: Mon, 3 Aug 2020 05:15:47 +0100 [thread overview]
Message-ID: <20200803041547.GZ23808@casper.infradead.org> (raw)
In-Reply-To: <20200802224652.6be413fe@Phenom-II-x6.niklas.com>
On Sun, Aug 02, 2020 at 10:46:52PM -0400, David Niklas wrote:
> The file: Documentation/admin-guide/bug-hunting.rst
> gives instructions on how to find the offending line of code using EIP.
> My particular bug that I need to report doesn't have EIP listed -- at
> least not by name. I tried to guess what EIP was in
> my case "__schedule+0x29e/0x6c0" but that didn't produce any results in
> gdb on my debug kernel.
EIP is the x86-32 name for what x86-64 calls RIP. Not much help in
this case, because it's pointing to a userspace address (actually, I
think it's the vdso).
> I don't appear to have the referenced module type problem:
> "[<ffffffff8802c8e9>] :jbd:log_wait_commit+0xa3/0xf5"
>
> I'm totally new to kernel debugging so the documentation is really
> important and I'm rather frustrated in even bothering to read it as it's
> incomplete/unhelpful.
>
> Here's the exact bug I'm trying to tackle.
>
> [68812.480447] INFO: task CacheThread_Blo:9414 blocked for more than 480
> seconds.
That's the important bit. Your task tried to take a mutex and 480
seconds later, it still didn't have it.
> [68812.480459] Not tainted 4.14.184-nopreempt-AMDGPU-dav9
> #1 [68812.480464] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message. [68812.480469] CacheThread_Blo D 0 9414 9082
> 0x00000080 [68812.480476] Call Trace:
> [68812.480494] __schedule+0x29e/0x6c0
> [68812.480505] schedule+0x32/0x80
> [68812.480513] schedule_preempt_disabled+0xa/0x10
> [68812.480520] __mutex_lock.isra.1+0x26b/0x4e0
> [68812.480550] ? do_journal_begin_r+0xbe/0x390 [reiserfs]
> [68812.480570] do_journal_begin_r+0xbe/0x390 [reiserfs]
The mutex it tried to take was in the function do_journal_begin_r().
Best of luck debugging reiserfs problems these days. It doesn't get
a lot of love.
prev parent reply other threads:[~2020-08-03 4:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 2:46 PROBLEM: Missing debug instructions when EIP is not present David Niklas
2020-08-03 4:15 ` Matthew Wilcox [this message]
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