linux-kernel - Re: [v1][PATCH 3/6] book3e/kgdb: update thread's dbcr0

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Message-Id: <A47C9236-0744-45BC-B25A-3DDEB05CD8A1@kernel.crashing.org>
Date:	Thu, 20 Dec 2012 12:41:53 -0600
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Tiejun Chen <tiejun.chen@...driver.com>
Cc:	<benh@...nel.crashing.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>, <jason.wessel@...driver.com>
Subject: Re: [v1][PATCH 3/6] book3e/kgdb: update thread's dbcr0


On Dec 20, 2012, at 3:08 AM, Tiejun Chen wrote:

> gdb always need to generate a single step properly to invoke
> a kgdb state. But with lazy interrupt, book3e can't always
> trigger a debug exception with a single step since the current
> is blocked for handling those pending exception, then we miss
> that expected dbcr configuration at last to generate a debug
> exception.
> 
> So here we also update thread's dbcr0 to make sure the current
> can go back with that missed dbcr0 configuration.
> 
> Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
> ---
> arch/powerpc/kernel/kgdb.c |   10 ++++++++++
> 1 file changed, 10 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
> index c470a40..516b44b 100644
> --- a/arch/powerpc/kernel/kgdb.c
> +++ b/arch/powerpc/kernel/kgdb.c
> @@ -426,8 +426,18 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> 		/* set the trace bit if we're stepping */
> 		if (remcom_in_buffer[0] == 's') {
> #ifdef CONFIG_PPC_ADV_DEBUG_REGS
> +#ifdef CONFIG_PPC_BOOK3E

Should this really be CONFIG_PPC64 or CONFIG_PPC_BOOK3E_64?

> +			/* With lazy interrut we have to update thread dbcr0 here
> +			 * to make sure we can set debug properly at last to invoke
> +			 * kgdb again to work well.
> +			 */
> +			current->thread.dbcr0 =
> +				mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
> +			mtspr(SPRN_DBCR0, current->thread.dbcr0);
> +#else
> 			mtspr(SPRN_DBCR0,
> 			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
> +#endif

Can we code this so we don't need the #else?

> 			linux_regs->msr |= MSR_DE;
> #else
> 			linux_regs->msr |= MSR_SE;
> -- 
> 1.7.9.5
> 
> --
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