linux-kernel - Re: [PATCH 1/5] MIPS: kdb: Remove old workaround for backtracing on other CPUs

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Message-ID: <20191114105125.t3jma3ghwj2wtv6w@holly.lan>
Date:   Thu, 14 Nov 2019 10:51:25 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Paul Burton <paul.burton@...s.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        qiaochong@...ngson.cn, kgdb-bugreport@...ts.sourceforge.net,
        ralf@...ux-mips.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        James Hogan <jhogan@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        Philippe Mathieu-Daudé <f4bug@...at.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/5] MIPS: kdb: Remove old workaround for backtracing on
 other CPUs

On Sat, Nov 09, 2019 at 11:16:40AM -0800, Douglas Anderson wrote:
> As of commit 2277b492582d ("kdb: Fix stack crawling on 'running' CPUs
> that aren't the master") we no longer need any special case for doing
> stack dumps on CPUs that are not the kdb master.  Let's remove.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> I have no way to test this personally, so hopefully someone who uses
> kdb/kgdb on MIPS can.

I took this as a hint to add mips support to kgdbtest ;-)

Support is added and working well. Unfortunately lack of familiarity
with mips means I have not yet figured out which mips defconfig gives
us working SMP (and what the corresponding qemu invocation should be).

I think that means I still can't (quite) exercise this code fully.
The most appropriate test is bta on an SMP system, right?


> Ideally this patch should be Acked by MIPS folks and then land through
> the kdb/kgdb tree since the next patch in the series, ("kdb:
> kdb_current_regs should be private") depends on it.

An Acked-by from a MIPS maintainer would be very welcome. Perhaps
with a bit of extra work on the above I might be able to provide
a Tested-by:.

I didn't see anything that particularly bothered me in the patches but
given we're already at -rc7 I'm inclined to target this patchset for 5.6
rather than 5.5.


Daniel.