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Date: Thu, 26 Sep 2013 15:45:33 -0500
From: Jason Wessel <jason.wessel@...driver.com>
To: Mike Travis <travis@....com>
CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Dimitri Sivanich <sivanich@....com>,
Hedi Berriche <hedi@....com>, <x86@...nel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/7] KGDB/KDB: add support for external NMI handler to
call KGDB/KDB.
On 09/23/2013 04:25 PM, Mike Travis wrote:
> This patch adds a kgdb_nmicallin() interface that can be used by
> external NMI handlers to call the KGDB/KDB handler. The primary need
> for this is for those types of NMI interrupts where all the CPUs
> have already received the NMI signal. Therefore no send_IPI(NMI)
> is required, and in fact it will cause a 2nd unhandled NMI to occur.
> This generates the "Dazed and Confuzed" messages.
>
> Since all the CPUs are getting the NMI at roughly the same time, it's not
> guaranteed that the first CPU that hits the NMI handler will manage to
> enter KGDB and set the dbg_master_lock before the slaves start entering.
> The new argument "send_ready" was added for KGDB to signal the NMI handler
> to release the slave CPUs for entry into KGDB.
>
> Signed-off-by: Mike Travis <travis@....com>
> Reviewed-by: Dimitri Sivanich <sivanich@....com>
> Reviewed-by: Hedi Berriche <hedi@....com>
One problem that I pointed out before and then you can add
Acked-by: Jason Wessel <jason.wessel@...driver.com>
> ---
> include/linux/kdb.h | 1 +
> include/linux/kgdb.h | 1 +
> kernel/debug/debug_core.c | 30 +++++++++++++++++++++++++++++-
> kernel/debug/debug_core.h | 1 +
> kernel/debug/kdb/kdb_debugger.c | 5 ++++-
> kernel/debug/kdb/kdb_main.c | 3 +++
> 6 files changed, 39 insertions(+), 2 deletions(-)
>
> --- linux.orig/include/linux/kdb.h
> +++ linux/include/linux/kdb.h
> @@ -109,6 +109,7 @@ typedef enum {
> KDB_REASON_RECURSE, /* Recursive entry to kdb;
> * regs probably valid */
> KDB_REASON_SSTEP, /* Single Step trap. - regs valid */
> + KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */
> } kdb_reason_t;
>
> extern int kdb_trap_printk;
> --- linux.orig/include/linux/kgdb.h
> +++ linux/include/linux/kgdb.h
> @@ -310,6 +310,7 @@ extern int
> kgdb_handle_exception(int ex_vector, int signo, int err_code,
> struct pt_regs *regs);
> extern int kgdb_nmicallback(int cpu, void *regs);
> +extern int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *snd_rdy);
> extern void gdbstub_exit(int status);
>
> extern int kgdb_single_step;
> --- linux.orig/kernel/debug/debug_core.c
> +++ linux/kernel/debug/debug_core.c
> @@ -575,8 +575,12 @@ 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)
> + atomic_set(ks->send_ready, 1);
> +
> /* Signal the other CPUs to enter kgdb_wait() */
> - if ((!kgdb_single_step) && kgdb_do_roundup)
> + else if ((!kgdb_single_step) && kgdb_do_roundup)
> kgdb_roundup_cpus(flags);
> #endif
>
> @@ -729,6 +733,30 @@ int kgdb_nmicallback(int cpu, void *regs
> return 0;
> }
> #endif
> + return 1;
> +}
> +
> +int kgdb_nmicallin(int cpu, int trapnr, void *regs, atomic_t *send_ready)
> +{
> +#ifdef CONFIG_SMP
> + if (!kgdb_io_ready(0) || !send_ready)
> + return 1;
> +
> + if (kgdb_info[cpu].enter_kgdb == 0) {
> + struct kgdb_state kgdb_var;
> + struct kgdb_state *ks = &kgdb_var;
> +
> + memset(ks, 0, sizeof(struct kgdb_state));
> + ks->cpu = cpu;
> + ks->ex_vector = trapnr;
> + ks->signo = SIGTRAP;
> + ks->err_code = KDB_REASON_SYSTEM_NMI;
> + ks->linux_regs = regs;
> + ks->send_ready = send_ready;
> + kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
> + return 0;
> + }
> +#endif
> return 1;
> }
>
> --- linux.orig/kernel/debug/debug_core.h
> +++ linux/kernel/debug/debug_core.h
> @@ -26,6 +26,7 @@ struct kgdb_state {
> unsigned long threadid;
> long kgdb_usethreadid;
> struct pt_regs *linux_regs;
> + atomic_t *send_ready;
> };
>
> /* Exception state values */
> --- linux.orig/kernel/debug/kdb/kdb_debugger.c
> +++ linux/kernel/debug/kdb/kdb_debugger.c
> @@ -69,7 +69,10 @@ int kdb_stub(struct kgdb_state *ks)
> if (atomic_read(&kgdb_setting_breakpoint))
> reason = KDB_REASON_KEYBOARD;
>
> - if (in_nmi())
> + if (ks->err_code == KDB_REASON_SYSTEM_NMI)
This should be:
(ks->err == KDB_REASON_SYSNMI && ks->signo == SIGTRAP)
Other arch's in their arch specific handling code may set ks->err differently. The err code is signal specific. For example:
arch/hexagon/kernel/kgdb.c: if (kgdb_handle_exception(args->trapnr & 0xff, args->signr, args->err,
The error passed in will be different for other signals and we do not want it to collide.
Cheers,
Jason.
> + reason = KDB_REASON_SYSTEM_NMI;
> +
> + else if (in_nmi())
> reason = KDB_REASON_NMI;
>
> for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) {
> --- linux.orig/kernel/debug/kdb/kdb_main.c
> +++ linux/kernel/debug/kdb/kdb_main.c
> @@ -1200,6 +1200,9 @@ static int kdb_local(kdb_reason_t reason
> instruction_pointer(regs));
> kdb_dumpregs(regs);
> break;
> + case KDB_REASON_SYSTEM_NMI:
> + kdb_printf("due to System NonMaskable Interrupt\n");
> + break;
> case KDB_REASON_NMI:
> kdb_printf("due to NonMaskable Interrupt @ "
> kdb_machreg_fmt "\n",
>
> --
>
--
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