From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Date: Thu, 09 Aug 2018 00:27:46 +0000 Subject: Re: [PATCH 10/20] powerpc/dma-noncoherent: don't disable irqs over kmap_atomic Message-Id: List-Id: References: <20180730163824.10064-1-hch@lst.de> <20180730163824.10064-11-hch@lst.de> In-Reply-To: <20180730163824.10064-11-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Hellwig , Paul Mackerras , Michael Ellerman , Tony Luck , Fenghua Yu Cc: Konrad Rzeszutek Wilk , Robin Murphy , linuxppc-dev@lists.ozlabs.org, iommu@lists.linux-foundation.org, linux-ia64@vger.kernel.org On Mon, 2018-07-30 at 18:38 +0200, Christoph Hellwig wrote: > The requirement to disable local irqs over kmap_atomic is long gone, > so remove those calls. Really ? I'm trying to verify that and getting lost in a mess of macros from hell in the per-cpu stuff but if you look at our implementation of kmap_atomic_prot(), all it does is a preempt_disable(), and then it uses kmap_atomic_idx_push(): int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1; Note the use of __this_cpu_inc_return(), not this_cpu_inc_return(), ie this is the non-interrupt safe version... Ben. > Signed-off-by: Christoph Hellwig > --- > arch/powerpc/mm/dma-noncoherent.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/arch/powerpc/mm/dma-noncoherent.c b/arch/powerpc/mm/dma-noncoherent.c > index 382528475433..d1c16456abac 100644 > --- a/arch/powerpc/mm/dma-noncoherent.c > +++ b/arch/powerpc/mm/dma-noncoherent.c > @@ -357,12 +357,10 @@ static inline void __dma_sync_page_highmem(struct page *page, > { > size_t seg_size = min((size_t)(PAGE_SIZE - offset), size); > size_t cur_size = seg_size; > - unsigned long flags, start, seg_offset = offset; > + unsigned long start, seg_offset = offset; > int nr_segs = 1 + ((size - seg_size) + PAGE_SIZE - 1)/PAGE_SIZE; > int seg_nr = 0; > > - local_irq_save(flags); > - > do { > start = (unsigned long)kmap_atomic(page + seg_nr) + seg_offset; > > @@ -378,8 +376,6 @@ static inline void __dma_sync_page_highmem(struct page *page, > cur_size += seg_size; > seg_offset = 0; > } while (seg_nr < nr_segs); > - > - local_irq_restore(flags); > } > #endif /* CONFIG_HIGHMEM */ >