linux-kernel - Re: [PATCH] mm, memory-failure: clarify error message

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Message-ID: <512532de-4c09-626d-380f-58cef519166b@arm.com>
Date:   Fri, 17 May 2019 10:18:02 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Jane Chu <jane.chu@...cle.com>, n-horiguchi@...jp.nec.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     linux-nvdimm@...ts.01.org
Subject: Re: [PATCH] mm, memory-failure: clarify error message



On 05/17/2019 09:38 AM, Jane Chu wrote:
> Some user who install SIGBUS handler that does longjmp out

What the longjmp about ? Are you referring to the mechanism of catching the
signal which was registered ?

> therefore keeping the process alive is confused by the error
> message
>   "[188988.765862] Memory failure: 0x1840200: Killing
>    cellsrv:33395 due to hardware memory corruption"

Its a valid point because those are two distinct actions.

> Slightly modify the error message to improve clarity.
> 
> Signed-off-by: Jane Chu <jane.chu@...cle.com>
> ---
>  mm/memory-failure.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index fc8b517..14de5e2 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -216,10 +216,9 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
>  	short addr_lsb = tk->size_shift;
>  	int ret;
>  
> -	pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
> -		pfn, t->comm, t->pid);
> -
>  	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
> +		pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory "
> +			"corruption\n", pfn, t->comm, t->pid);
>  		ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr,
>  				       addr_lsb, current);
>  	} else {
> @@ -229,6 +228,8 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
>  		 * This could cause a loop when the user sets SIGBUS
>  		 * to SIG_IGN, but hopefully no one will do that?
>  		 */
> +		pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware "
> +			"memory corruption\n", pfn, t->comm, t->pid);
>  		ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
>  				      addr_lsb, t);  /* synchronous? */

As both the pr_err() messages are very similar, could not we just switch between "Killing"
and "Sending SIGBUS to" based on a variable e.g action_[kill|sigbus] evaluated previously
with ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm).