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

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Date:   Fri, 17 May 2019 18:20:35 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "jane.chu@...cle.com" <jane.chu@...cle.com>,
        "n-horiguchi@...jp.nec.com" <n-horiguchi@...jp.nec.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: Re: [PATCH] mm, memory-failure: clarify error message

On Thu, 2019-05-16 at 22:08 -0600, Jane Chu wrote:
> Some user who install SIGBUS handler that does longjmp out
> therefore keeping the process alive is confused by the error
> message
>   "[188988.765862] Memory failure: 0x1840200: Killing
>    cellsrv:33395 due to hardware memory corruption"
> 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);

Minor nit, but the string shouldn't be split over multiple lines to
preserve grep-ability. In such a case it is usually considered OK to
exceed 80 characters for the line if needed.

>  		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? */
>  	}