linux-kernel - Re: [PATCH] powerpc: Clean up tm_abort duplication in hash_utils

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Date:   Thu, 01 Sep 2016 12:46:40 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     Rui Teng <rui.teng@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, paulus@...ba.org
Subject: Re: [PATCH] powerpc: Clean up tm_abort duplication in hash_utils_64.c

Am Freitag, 26 August 2016, 11:50:10 schrieb Rui Teng:
> The same logic appears twice and should probably be pulled out into a
> function.
> 
> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
> Signed-off-by: Rui Teng <rui.teng@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/mm/hash_utils_64.c | 45
> +++++++++++++++++------------------------ 1 file changed, 19
> insertions(+), 26 deletions(-)
> 
> diff --git a/arch/powerpc/mm/hash_utils_64.c
> b/arch/powerpc/mm/hash_utils_64.c index 0821556..69ef702 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -1460,6 +1460,23 @@ out_exit:
>  	local_irq_restore(flags);
>  }
> 
> +/*
> + * Transactions are not aborted by tlbiel, only tlbie.
> + * Without, syncing a page back to a block device w/ PIO could pick up
> + * transactional data (bad!) so we force an abort here.  Before the
> + * sync the page will be made read-only, which will flush_hash_page.
> + * BIG ISSUE here: if the kernel uses a page from userspace without
> + * unmapping it first, it may see the speculated version.
> + */
> +void local_tm_abort(int local)
> +{
> +	if (local && cpu_has_feature(CPU_FTR_TM) && current->thread.regs &&
> +		MSR_TM_ACTIVE(current->thread.regs->msr)) {
> +		tm_enable();
> +		tm_abort(TM_CAUSE_TLBI);
> +	}
> +}
> +

Since local_tm_abort is only used in this file, it should be static.

Also, since both places calling it are guarded by 
CONFIG_PPC_TRANSACTIONAL_MEM, wouldn't it be cleaner if the #ifdef was here 
instead and the #else block defined an empty static inline function? Then 
the call sites wouldn't need to be guarded.

-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center