Re: [PATCH v2] Move precessing of MCE queued event out from syscall exit path.

[Hugh Dickins <hughd@google.com>]

On Tue, 14 Jan 2014, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> Huge Dickins reported an issue that b5ff4211a829
> "powerpc/book3s: Queue up and process delayed MCE events" breaks the
> PowerMac G5 boot. This patch fixes it by moving the mce even processing
> away from syscall exit, which was wrong to do that in first place, and
> using irq work framework to delay processing of mce event.
> 
> Reported-by: Hugh Dickins <hughd@google.com
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

This version also boots and runs fine for me on the G5
(but of course, I'm probably not testing delayed MCE events at all).

Hugh

> ---
>  arch/powerpc/include/asm/mce.h |    1 -
>  arch/powerpc/kernel/entry_64.S |    5 -----
>  arch/powerpc/kernel/mce.c      |   13 ++++++++++---
>  3 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
> index 2257d1e..f97d8cb 100644
> --- a/arch/powerpc/include/asm/mce.h
> +++ b/arch/powerpc/include/asm/mce.h
> @@ -192,7 +192,6 @@ extern void save_mce_event(struct pt_regs *regs, long handled,
>  extern int get_mce_event(struct machine_check_event *mce, bool release);
>  extern void release_mce_event(void);
>  extern void machine_check_queue_event(void);
> -extern void machine_check_process_queued_event(void);
>  extern void machine_check_print_event_info(struct machine_check_event *evt);
>  extern uint64_t get_mce_fault_addr(struct machine_check_event *evt);
>  
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 770d6d6..bbfb029 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -184,11 +184,6 @@ syscall_exit:
>  	bl	.do_show_syscall_exit
>  	ld	r3,RESULT(r1)
>  #endif
> -#ifdef CONFIG_PPC_BOOK3S_64
> -BEGIN_FTR_SECTION
> -	bl	.machine_check_process_queued_event
> -END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
> -#endif
>  	CURRENT_THREAD_INFO(r12, r1)
>  
>  	ld	r8,_MSR(r1)
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index d6edf2b..a7fd4cb 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -26,6 +26,7 @@
>  #include <linux/ptrace.h>
>  #include <linux/percpu.h>
>  #include <linux/export.h>
> +#include <linux/irq_work.h>
>  #include <asm/mce.h>
>  
>  static DEFINE_PER_CPU(int, mce_nest_count);
> @@ -35,6 +36,11 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event);
>  static DEFINE_PER_CPU(int, mce_queue_count);
>  static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event_queue);
>  
> +static void machine_check_process_queued_event(struct irq_work *work);
> +struct irq_work mce_event_process_work = {
> +        .func = machine_check_process_queued_event,
> +};
> +
>  static void mce_set_error_info(struct machine_check_event *mce,
>  			       struct mce_error_info *mce_err)
>  {
> @@ -185,17 +191,19 @@ void machine_check_queue_event(void)
>  		return;
>  	}
>  	__get_cpu_var(mce_event_queue[index]) = evt;
> +
> +	/* Queue irq work to process this event later. */
> +	irq_work_queue(&mce_event_process_work);
>  }
>  
>  /*
>   * process pending MCE event from the mce event queue. This function will be
>   * called during syscall exit.
>   */
> -void machine_check_process_queued_event(void)
> +static void machine_check_process_queued_event(struct irq_work *work)
>  {
>  	int index;
>  
> -	preempt_disable();
>  	/*
>  	 * For now just print it to console.
>  	 * TODO: log this error event to FSP or nvram.
> @@ -206,7 +214,6 @@ void machine_check_process_queued_event(void)
>  				&__get_cpu_var(mce_event_queue[index]));
>  		__get_cpu_var(mce_queue_count)--;
>  	}
> -	preempt_enable();
>  }
>  
>  void machine_check_print_event_info(struct machine_check_event *evt)
> 
>