Re: [PATCH 1/1] PATCH: KGDB/KDB Fix no KDB config problem.

From: Ingo Molnar
Date: Thu Oct 03 2013 - 13:15:33 EST



* Mike Travis <travis@xxxxxxx> wrote:

>
>
> On 10/3/2013 9:51 AM, Ingo Molnar wrote:
> >
> > * Mike Travis <travis@xxxxxxx> wrote:
> >
> >> Some code added to the debug_core module had KDB dependencies
> >> that it shouldn't have.
> >>
> >> Signed-off-by: Mike Travis <travis@xxxxxxx>
> >> ---
> >> 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
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