Re: [PATCH 1/4] parisc: disable preemption during local tlb flush

[Sven Schnelle <svens@stackframe.org>]

Sven Schnelle <svens@stackframe.org> writes:

> flush_cache_mm() fetches %sr3 via mtsp(3). If it matches mm->context,
> it flushes caches and the TLB. However, the TLB is cpu-local, so if the
> code gets preempted shortly after the mtsp(), and later resumed on another
> CPU, the wrong TLB is flushed.
>
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> ---
>  arch/parisc/kernel/cache.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
> index 39e02227e231..90656c49bc07 100644
> --- a/arch/parisc/kernel/cache.c
> +++ b/arch/parisc/kernel/cache.c
> @@ -558,6 +558,7 @@ void flush_cache_mm(struct mm_struct *mm)
>  		return;
>  	}
>  
> +	preempt_disable();
>  	if (mm->context == mfsp(3)) {
>  		for (vma = mm->mmap; vma; vma = vma->vm_next) {
>  			flush_user_dcache_range_asm(vma->vm_start, vma->vm_end);
> @@ -565,8 +566,10 @@ void flush_cache_mm(struct mm_struct *mm)
>  				flush_user_icache_range_asm(vma->vm_start, vma->vm_end);
>  			flush_tlb_range(vma, vma->vm_start, vma->vm_end);
>  		}
> +		preempt_enable();
>  		return;
>  	}
> +	preempt_enable();
>  
>  	pgd = mm->pgd;
>  	for (vma = mm->mmap; vma; vma = vma->vm_next) {

I noticed that flush_cache_range() has the same problem. Helge, let me
know whether i should send a v2 with an additional patch, or a single
follow up patch. Both functions also look very similar, so i think
best would be to combine the code of these two functions.