lkml.org 
[lkml]   [2013]   [Dec]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 2/8] x86: allow to call text_poke_bp during boot
On Tue, Dec 10, 2013 at 04:42:14PM +0100, Petr Mladek wrote:
> We would like to use text_poke_bp in ftrace. It might be called also during
> boot when there is only one CPU and we do not need to sync the others.
>
> The check is must to have because there are also disabled interrupts during
> the boot. Then the call would cause a deadlock, see the warning in
> "smp_call_function_many", kernel/smp.c:371.
>
> The change is inspired by the code in arch/x86/kernel/ftrace.c.
>
> Signed-off-by: Petr Mladek <pmladek@suse.cz>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> ---
> arch/x86/kernel/alternative.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index eabed9326d2a..6436beec7b0c 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -599,6 +599,17 @@ static void do_sync_core(void *info)
> sync_core();
> }
>
> +static void run_sync(void)

Can we call this sync_cores()?

It is what it does. :)

> +{
> + /*
> + * We do not need to sync other cores during boot when there is only one
> + * CPU enabled. In fact, we must not because there are also disabled
> + * interrupts. The call would fail because of a potential deadlock.
> + */
> + if (num_online_cpus() != 1)
> + on_each_cpu(do_sync_core, NULL, 1);
> +}

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--


\
 
 \ /
  Last update: 2013-12-10 17:01    [W:0.206 / U:0.616 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site