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Date: Sun, 10 Feb 2008 09:21:32 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Christoph Hellwig <hch@...radead.org>
Cc: linux-kernel@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@....com.au>,
Thomas Gleixner <tglx@...utronix.de>,
Jason Wessel <jason.wessel@...driver.com>
Subject: Re: [3/6] kgdb: core
* Ingo Molnar <mingo@...e.hu> wrote:
> > It's all in the thread starting with '[PATCH 0/8] kgdb 2.6.25
> > version', msgid
> > 1202564114-18587-1-git-send-email-jason.wessel@...driver.com or at
> > http://lkml.org/lkml/2008/2/9/104
>
> thanks - i found Sam's mail meanwhile and addressed most of the
> observations and updated the kgdb.git tree. I'll now check the threads
> above whether i missed anything. (feel free to point it out if you
> notice anything outright) As the changes have been janitorial only i
> refrain from reposting the series once again. The latest shortlog is
> below.
i've read all that thread now and i think all your observations are
addressed in the latest tree i posted. In fact, most of the
non-syntactic observations you made i already addressed in my series
from yesterday. Find the latest tree at:
git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-kgdb.git
with tip commit 8fbf71f7636bd26843de01b4bdf819c9a9777427. Shortlog and
diffstat below. I backmerged all the fixlets into their original
commits, to keep the splitup clean.
Here are my replies to your feedback:
Date: Sat, 9 Feb 2008 12:10:26 -0500
From: Christoph Hellwig <hch@...radead.org>
To: jason.wessel@...driver.com
Subject: Re: [PATCH 2/8] pid, kgdb: add pid_max prototype
addressed.
Date: Sat, 9 Feb 2008 12:15:03 -0500
From: Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 3/8] kgdb, modules: Always allow module sect info for
addressed: this was mooted by my original posting from yesterday
already - i removed this complication.
Date: Sat, 9 Feb 2008 12:16:05 -0500
From: Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 4/8] kgdb: COPTIMIZE flag
addressed: this was mooted by my original posting from yesterday
already - i removed this complication.
> > + * include/asm-generic/kgdb.h
>
> Please don't mention the file name in the top-of-file comments. This
> information is redundant and will easily get out of date when moving
> files around or copying them. Note that this applies to basically any
> file in this patch.
fixed.
> > +#ifdef CONFIG_X86
> > +/**
> > + * kgdb_skipexception - Bail of of KGDB when we've been triggered.
>
> arch ifdefs don't belong into an asm-generic/ file. Please have a
> proper asm-x86/kgdb.h that defines these things.
addressed: this was fixed in my submission yesterday.
> Kerneldoc comments don't belong above the prototype of a function but
> the function body.
disagree - the best is to have it in both places - and in many places we
do that. Anyway, this is up to maintainer discretion.
> > +#ifdef CONFIG_KGDB_ARCH_HAS_SHADOW_INFO
> > +/**
> > + * kgdb_shadowinfo - Get shadowed information on @threadid.
> > + * @regs: The &struct pt_regs of the current process.
> > + * @buffer: A buffer of %BUFMAX size.
> > + * @threadid: The thread id of the shadowed process to get information on.
> > + */
> > +extern void kgdb_shadowinfo(struct pt_regs *regs, char *buffer,
> > + unsigned threadid);
>
> I don't really thing this belongs into an asm-generic header, again.
> ARchitectures having shadow info should just provide this in their own
> asm-foo/kgdb.h. Or better yet just kill it for the first submission.
disagree. Many architectures will select shadow-info support so having
this in asm-generic/kgdb.h is straightforward. I am actually an
architecture who had to deal with this stuff in 32-bit (no shadow info
support) and 64-bit (shadow info support) and this was handy and
obvious. (But note that the patch submitted by Jason had a few
uglinesses in this area that i fixed so please re-check the ones in my
tree.)
> > +struct debuggerinfo_struct {
> > + void *debuggerinfo;
> > + struct task_struct *task;
> > +} kgdb_info[NR_CPUS];
>
> shouldn't this use per-cpu data? Or is that in some way to fragile
> for a debugger?
yes, eventually we might want to use kgdb earlier than the per CPU areas
are set up.
> > +/* reboot notifier block */
> > +static struct notifier_block kgdb_reboot_notifier = {
> > + .notifier_call = kgdb_notify_reboot,
> > + .next = NULL,
> > + .priority = INT_MAX,
> > +};
>
> No need to initialize fields to 0 or NULL in static variables.
agreed, fixed.
> > + if ((ch >= 'a') && (ch <= 'f'))
> > + return ch - 'a' + 10;
> > + if ((ch >= '0') && (ch <= '9'))
> > + return ch - '0';
> > + if ((ch >= 'A') && (ch <= 'F'))
> > + return ch - 'A' + 10;
>
> lots of superflous braces. More of them later in this file in the
> same style.
maintainer discretion item. I prefer having such clarity in operator
ordering.
> > +#ifdef __BIG_ENDIAN
> > + *buf++ = hexchars[(tmp_s >> 12) & 0xf];
> > + *buf++ = hexchars[(tmp_s >> 8) & 0xf];
> > + *buf++ = hexchars[(tmp_s >> 4) & 0xf];
> > + *buf++ = hexchars[tmp_s & 0xf];
> > +#else
> > + *buf++ = hexchars[(tmp_s >> 4) & 0xf];
> > + *buf++ = hexchars[tmp_s & 0xf];
> > + *buf++ = hexchars[(tmp_s >> 12) & 0xf];
> > + *buf++ = hexchars[(tmp_s >> 8) & 0xf];
> > +#endif
>
> This is really ugly, but I don't really know a good way around it
> either.
yeah. Agreed about the ugliness and i volunteer to implement any
sensible suggestions later on :-)
> > + if (arch_kgdb_ops.shadowth &&
> > + ks->kgdb_usethreadid >= pid_max + num_online_cpus()) {
>
> if (arch_kgdb_ops.shadowth &&
> ks->kgdb_usethreadid >= pid_max + num_online_cpus()) {
>
> similar odd indentation in a few other spots.
check out the full context, not just the patch. It's often done for a
reason to make the full visual appearance of that particular code nice.
> > +menuconfig KGDB
> > + bool "KGDB: kernel debugging with remote gdb"
> > + select KGDB_ARCH_HAS_SHADOW_INFO if X86_64
>
> Why can't this be set in the X86_64 config?
addressed: it is in my series.
> > + select DEBUG_INFO
> > + select FRAME_POINTER
>
> I think these two would be better as depends on
selecting FRAME_POINTER is totally sensible and other debugging code
does it too. I agree about the DEBUG_INFO and it was addressed in
yesterday's series already.
Ingo
------------------>
Ingo Molnar (3):
pids: add pid_max prototype
uaccess: add probe_kernel_write()
x86: kgdb support
Jan Kiszka (1):
consoles: polling support, kgdboc
Jason Wessel (2):
kgdb: core
kgdb: document parameters
Documentation/kernel-parameters.txt | 5 +
arch/x86/Kconfig | 4 +
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/kgdb.c | 550 ++++++++++
drivers/char/tty_io.c | 47 +
drivers/serial/8250.c | 62 ++
drivers/serial/Kconfig | 3 +
drivers/serial/Makefile | 1 +
drivers/serial/kgdboc.c | 164 +++
drivers/serial/serial_core.c | 67 ++-
include/asm-generic/kgdb.h | 91 ++
include/asm-x86/kgdb.h | 87 ++
include/linux/kgdb.h | 264 +++++
include/linux/pid.h | 2 +
include/linux/serial_core.h | 4 +
include/linux/tty_driver.h | 12 +
include/linux/uaccess.h | 22 +
kernel/Makefile | 1 +
kernel/kgdb.c | 2019 +++++++++++++++++++++++++++++++++++
kernel/sysctl.c | 2 +-
lib/Kconfig.debug | 2 +
lib/Kconfig.kgdb | 37 +
22 files changed, 3445 insertions(+), 2 deletions(-)
create mode 100644 arch/x86/kernel/kgdb.c
create mode 100644 drivers/serial/kgdboc.c
create mode 100644 include/asm-generic/kgdb.h
create mode 100644 include/asm-x86/kgdb.h
create mode 100644 include/linux/kgdb.h
create mode 100644 kernel/kgdb.c
create mode 100644 lib/Kconfig.kgdb
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