linux-kernel - [kgdb:kgdb-next] KGDB: BP remove failed: ffffffff81026ed0

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Date:	Tue, 10 Jul 2012 10:58:35 +0800
From:	wfg@...ux.intel.com
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: [kgdb:kgdb-next] KGDB: BP remove failed: ffffffff81026ed0

Hi Jason,

This HEAD commit in kgdb-next makes kgdb boot time tests freeze.
The kernel is tested inside kvm with the attached config.

3751d3e85cf693e10e2c47c03c8caa65e171099b is the first bad commit
commit 3751d3e85cf693e10e2c47c03c8caa65e171099b
Author: Jason Wessel <jason.wessel@...driver.com>
Date:   Fri Mar 23 09:35:05 2012 -0500

    x86,kgdb: Fix DEBUG_RODATA limitation using text_poke()

    There has long been a limitation using software breakpoints with a
    kernel compiled with CONFIG_DEBUG_RODATA going back to 2.6.26. For
    this particular patch, it will apply cleanly and has been tested all
    the way back to 2.6.36.

    The kprobes code uses the text_poke() function which accommodates
    writing a breakpoint into a read-only page.  The x86 kgdb code can
    solve the problem similarly by overriding the default breakpoint
    set/remove routines and using text_poke() directly.

    The x86 kgdb code will first attempt to use the traditional
    probe_kernel_write(), and next try using a the text_poke() function.
    The break point install method is tracked such that the correct break
    point removal routine will get called later on.

    Cc: x86@...nel.org
    Cc: Thomas Gleixner <tglx@...utronix.de>
    Cc: Ingo Molnar <mingo@...hat.com>
    Cc: H. Peter Anvin <hpa@...or.com>
    Cc: stable@...r.kernel.org # >= 2.6.36
    Inspried-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
    Signed-off-by: Jason Wessel <jason.wessel@...driver.com>

:040000 040000 a06ac46574fcf63533d558f52c2b6b116f3c5db4 cccfa3e5eeab293de1a8b4858624fffca86dd95b M      arch
:040000 040000 5a989b035ad4054136ce69869ad4979d0ad73207 dc27a5810e1469b596dd82481c4d1a594e21f0bc M      drivers
:040000 040000 ca2ec2c143aea2a044d656b3df461a5067043b56 8980fef454edd7e18e353c81593a208badb4833f M      include
bisect run success

Thanks,
Fengguang

View attachment "dmesg-kvm-stoakley-27984-2012-07-10-00-02-27" of type "text/plain" (105352 bytes)

View attachment "config-3.5.0-rc4+" of type "text/plain" (76938 bytes)