linux-kernel - Re: [PATCH v2] kernel/panic/kexec: fix "crash_kexec_post

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Date:	Mon, 23 Mar 2015 11:47:52 +0800
From:	Baoquan He <bhe@...hat.com>
To:	"Hatayama, Daisuke/畑山 大輔" 
	<d.hatayama@...fujitsu.com>
Cc:	ebiederm@...ssion.com, Vivek Goyal <vgoyal@...hat.com>,
	masami.hiramatsu.pt@...achi.com, hidehiro.kawai.ez@...achi.com,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	akpm@...ux-foundation.org, mingo@...hat.com, bp@...e.de
Subject: Re: [PATCH v2] kernel/panic/kexec: fix "crash_kexec_post_notifiers"
 option issue in oops path

CC more people ...

On 03/07/15 at 01:31am, "Hatayama, Daisuke/畑山 大輔" wrote:
> The commit f06e5153f4ae2e2f3b0300f0e260e40cb7fefd45 introduced
> "crash_kexec_post_notifiers" kernel boot option, which toggles
> wheather panic() calls crash_kexec() before panic_notifiers and dump
> kmsg or after.
> 
> The problem is that the commit overlooks panic_on_oops kernel boot
> option. If it is enabled, crash_kexec() is called directly without
> going through panic() in oops path.
> 
> To fix this issue, this patch adds a check to
> "crash_kexec_post_notifiers" in the condition of kexec_should_crash().
> 
> Also, put a comment in kexec_should_crash() to explain not obvious
> things on this patch.
> 
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> Acked-by: Baoquan He <bhe@...hat.com>
> Tested-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> ---
>  include/linux/kernel.h |  3 +++
>  kernel/kexec.c         | 11 +++++++++++
>  kernel/panic.c         |  2 +-
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index d6d630d..07483c7 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -426,6 +426,9 @@ extern int panic_on_unrecovered_nmi;
>  extern int panic_on_io_nmi;
>  extern int panic_on_warn;
>  extern int sysctl_panic_on_stackoverflow;
> +
> +extern bool crash_kexec_post_notifiers;
> +
>  /*
>   * Only to be used by arch init code. If the user over-wrote the default
>   * CONFIG_PANIC_TIMEOUT, honor it.
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 38c25b1..5bf6077 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -84,6 +84,17 @@ struct resource crashk_low_res = {
> 
>  int kexec_should_crash(struct task_struct *p)
>  {
> +	/*
> +	 * If crash_kexec_post_notifiers is enabled, don't run
> +	 * crash_kexec() here yet, which must be run after panic
> +	 * notifiers in panic().
> +	 */
> +	if (crash_kexec_post_notifiers)
> +		return 0;
> +	/*
> +	 * There are 4 panic() calls in do_exit() path, each of which
> +	 * calls corresponds to each of these 4 conditions.
> +	 */
>  	if (in_interrupt() || !p->pid || is_global_init(p) || panic_on_oops)
>  		return 1;
>  	return 0;
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 8136ad7..79ca912 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -32,7 +32,7 @@ static unsigned long tainted_mask;
>  static int pause_on_oops;
>  static int pause_on_oops_flag;
>  static DEFINE_SPINLOCK(pause_on_oops_lock);
> -static bool crash_kexec_post_notifiers;
> +bool crash_kexec_post_notifiers;
>  int panic_on_warn __read_mostly;
> 
>  int panic_timeout = CONFIG_PANIC_TIMEOUT;
> -- 
> 1.9.3
> 
> 
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