Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751962Ab3JDGat (ORCPT ); Fri, 4 Oct 2013 02:30:49 -0400 Received: from mail-ea0-f182.google.com ([209.85.215.182]:39136 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750842Ab3JDGas (ORCPT ); Fri, 4 Oct 2013 02:30:48 -0400 Date: Fri, 4 Oct 2013 08:30:44 +0200 From: Ingo Molnar To: Mike Travis Cc: Ingo Molnar , Jason Wessel , Peter Zijlstra , Paul Mackerras , Arnaldo Carvalho de Melo , "H. Peter Anvin" , Thomas Gleixner , Andrew Morton , Dimitri Sivanich , Hedi Berriche , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] PATCH: KGDB/KDB Fix no KDB config problem. Message-ID: <20131004063043.GF11399@gmail.com> References: <20131003163824.966169920@asylum.americas.sgi.com> <20131003163825.184494258@asylum.americas.sgi.com> <20131003165122.GB32755@gmail.com> <524DA381.2050108@sgi.com> <20131003171520.GA5144@gmail.com> <524DAF17.8040104@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <524DAF17.8040104@sgi.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4657 Lines: 130 * Mike Travis wrote: > > > On 10/3/2013 10:15 AM, Ingo Molnar wrote: > > > > * Mike Travis wrote: > > > >> > >> > >> On 10/3/2013 9:51 AM, Ingo Molnar wrote: > >>> > >>> * Mike Travis wrote: > >>> > >>>> Some code added to the debug_core module had KDB dependencies > >>>> that it shouldn't have. > >>>> > >>>> Signed-off-by: Mike Travis > >>>> --- > >>>> kernel/debug/debug_core.c | 8 ++++---- > >>>> kernel/debug/debug_core.h | 2 ++ > >>>> 2 files changed, 6 insertions(+), 4 deletions(-) > >>>> > >>>> --- linux.orig/kernel/debug/debug_core.c > >>>> +++ linux/kernel/debug/debug_core.c > >>>> @@ -575,8 +575,8 @@ return_normal: > >>>> raw_spin_lock(&dbg_slave_lock); > >>>> > >>>> #ifdef CONFIG_SMP > >>>> - /* If SYSTEM_NMI, slaves are already waiting */ > >>>> - if (ks->err_code == KDB_REASON_SYSTEM_NMI) > >>>> + /* If send_ready set, slaves are already waiting */ > >>>> + if (ks->send_ready) > >>>> atomic_set(ks->send_ready, 1); > >>>> > >>>> /* Signal the other CPUs to enter kgdb_wait() */ > >>>> @@ -682,11 +682,11 @@ kgdb_handle_exception(int evector, int s > >>>> if (arch_kgdb_ops.enable_nmi) > >>>> arch_kgdb_ops.enable_nmi(0); > >>>> > >>>> + memset(ks, 0, sizeof(struct kgdb_state)); > >>>> ks->cpu = raw_smp_processor_id(); > >>>> ks->ex_vector = evector; > >>>> ks->signo = signo; > >>>> ks->err_code = ecode; > >>>> - ks->kgdb_usethreadid = 0; > >>>> ks->linux_regs = regs; > >>>> > >>>> if (kgdb_reenter_check(ks)) > >>>> @@ -750,7 +750,7 @@ int kgdb_nmicallin(int cpu, int trapnr, > >>>> ks->cpu = cpu; > >>>> ks->ex_vector = trapnr; > >>>> ks->signo = SIGTRAP; > >>>> - ks->err_code = KDB_REASON_SYSTEM_NMI; > >>>> + ks->err_code = KGDB_KDB_REASON_SYSTEM_NMI; > >>>> ks->linux_regs = regs; > >>>> ks->send_ready = send_ready; > >>>> kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); > >>>> --- linux.orig/kernel/debug/debug_core.h > >>>> +++ linux/kernel/debug/debug_core.h > >>>> @@ -75,11 +75,13 @@ extern int kdb_stub(struct kgdb_state *k > >>>> extern int kdb_parse(const char *cmdstr); > >>>> extern int kdb_common_init_state(struct kgdb_state *ks); > >>>> extern int kdb_common_deinit_state(void); > >>>> +#define KGDB_KDB_REASON_SYSTEM_NMI KDB_REASON_SYSTEM_NMI > >>>> #else /* ! CONFIG_KGDB_KDB */ > >>>> static inline int kdb_stub(struct kgdb_state *ks) > >>>> { > >>>> return DBG_PASS_EVENT; > >>>> } > >>>> +#define KGDB_KDB_REASON_SYSTEM_NMI 0 > >>>> #endif /* CONFIG_KGDB_KDB */ > >>>> > >>>> #endif /* _DEBUG_CORE_H_ */ > >>> > >>> Hm, the KGDB_KDB_REASON_SYSTEM_NMI definition is a bit ugly. I still think > >>> there are layering violations here and just kludging it around doesn't > >>> solve it - a helper function that keeps kgdb details to the kgdb code > >>> would. > >>> > >>> Anyway, if Jason is fine with this solution and upholds his Acked-by then > >>> I'll merge this into the first patch and apply the two patches. > >>> > >>> Thanks, > >>> > >>> Ingo > >>> > >> > >> Would you prefer a simple #ifdef CONFIG_KGDB_KDB around the assignment? > > > > An #ifdef doesn't solve the layering violation! > > > > kernel/debug/debug_core.c didn't have any serious use of #ifdef > > CONFIG_KGDB_KDB before (it used it to flavor a few printks) and I'm not > > convinced it needs one for this feature either. > > > > So if that whole chunk is kdb dependent, why not shuffle that into a > > nicely named function and host it somewhere appropriate in > > kernel/debug/kdb/? That function would turn into an empty inline function > > in the !CONFIG_KGDB_KDB case. > > > > But ... it's up to Jason really whether he wants to abstract that piece of > > code out, I'm just kibitzing here really. > > > > Thanks, > > > > Ingo > > > > If I moved it to KDB then we would lose the capability to enter KGDB > mode and the gdb_stub functionality. The #ifdef could have a comment to > this effect? No, this really suggests that there's something else broken around there. Removing #ifdefs around non-trivial code and architecting it properly really makes things more reviewable, easier to understand, better specified and generally less bug prone. So adding an #ifdef around a pair of printk()s is probably OK - anything that is longer than a line probably deserves abstracted out. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/