[PATCH 1/2] powerpc: System reset avoid interleaving oops using die synchronisation

[David Gibson]

On Sun, Dec 24, 2017 at 02:49:22AM +1000, Nicholas Piggin wrote:
> The die() oops path contains a serializing lock to prevent oops
> messages from being interleaved. In the case of a system reset
> initiated oops (e.g., qemu nmi command), __die was being called
> which lacks that synchronisation and oops reports could be
> interleaved across CPUs.
> 
> A recent patch 4388c9b3a6ee7 ("powerpc: Do not send system reset
> request through the oops path") changed this to __die to avoid
> the debugger() call, but there is no real harm to calling it twice
> if the first time fell through. So go back to using die() here.
> This was observed to fix the problem.
> 
> Fixes: 4388c9b3a6ee7 ("powerpc: Do not send system reset request through the oops path")
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Reviewed-by: David Gibson <david at gibson.dropbear.id.au>

> ---
>  arch/powerpc/kernel/traps.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index f3eb61be0d30..109989676776 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -337,7 +337,7 @@ void system_reset_exception(struct pt_regs *regs)
>  	 * No debugger or crash dump registered, print logs then
>  	 * panic.
>  	 */
> -	__die("System Reset", regs, SIGABRT);
> +	die("System Reset", regs, SIGABRT);
>  
>  	mdelay(2*MSEC_PER_SEC); /* Wait a little while for others to print */
>  	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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