On Thu, 2013-06-20 at 18:28 +0800, Tiejun Chen wrote:
> When we're in kgdb_singlestep(), we have to work around to get
> thread_info by copying from the kernel stack before calling
> kgdb_handle_exception(), then copying it back afterwards.
>
> But for PPC64, we have a lazy interrupt implementation. So after
> copying thread info frome kernle stack, if we need to replay an
> interrupt, we shouldn't restore that previous backup thread info
> to make sure we can replay an interrupt lately with a proper
> thread info.
Explain why copying it would be a problem.
> This patch use __check_irq_replay() to guarantee this process.
>
> Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com>
> ---
> arch/powerpc/kernel/irq.c | 10 ++++++++++
> arch/powerpc/kernel/kgdb.c | 3 ++-
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> index ea185e0..3625453 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -339,7 +339,17 @@ bool prep_irq_for_idle(void)
> return true;
> }
>
> +notrace unsigned int check_irq_replay(void)
> +{
> + return __check_irq_replay();
> +}
> +#else
> +notrace unsigned int check_irq_replay(void)
> +{
> + return 0;
> +}
> #endif /* CONFIG_PPC64 */
> +EXPORT_SYMBOL(check_irq_replay);
>
> int arch_show_interrupts(struct seq_file *p, int prec)
> {
> diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
> index cde7818..5b30408 100644
> --- a/arch/powerpc/kernel/kgdb.c
> +++ b/arch/powerpc/kernel/kgdb.c
> @@ -152,6 +152,7 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
> }
>
> static DEFINE_PER_CPU(struct thread_info, kgdb_thread_info);
> +extern notrace unsigned int check_irq_replay(void);
Please put prototypes in headers rather than C files. Also, "extern" is
unnecessary on function prototypes.
> static int kgdb_singlestep(struct pt_regs *regs)
> {
> struct thread_info *thread_info, *exception_thread_info;
> @@ -181,7 +182,7 @@ static int kgdb_singlestep(struct pt_regs *regs)
>
> kgdb_handle_exception(0, SIGTRAP, 0, regs);
>
> - if (thread_info != exception_thread_info)
> + if ((thread_info != exception_thread_info) && (!check_irq_replay()))
Unnecessary parentheses.
Are you sure it's safe to call this here? Won't __check_irq_replay()
clear the pending event and PACA_IRQ_HARD_DIS?
-Scott
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