Messages in this thread | | | Date | Tue, 9 Apr 2013 20:53:18 -0700 | Subject | Re: [RFC PATCH 1/3] pstore-ram: use write-combine mappings | From | Colin Cross <> |
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On Tue, Apr 9, 2013 at 8:08 PM, Rob Herring <robherring2@gmail.com> wrote: > From: Rob Herring <rob.herring@calxeda.com> > > Atomic operations are undefined behavior on ARM for device or strongly > ordered memory types. So use write-combine variants for mappings. This > corresponds to normal, non-cacheable memory on ARM. For many other > architectures, this change should not change the mapping type.
This is going to make ramconsole less reliable. A debugging printk followed by a __raw_writel that causes an immediate hard crash is likely to lose the last updates, including the most useful message, in the write buffers.
Also, isn't this patch unnecessary after patch 3 in this set?
> Signed-off-by: Rob Herring <rob.herring@calxeda.com> > Cc: Anton Vorontsov <cbouatmailru@gmail.com> > Cc: Colin Cross <ccross@android.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Tony Luck <tony.luck@intel.com> > Cc: linux-kernel@vger.kernel.org > --- > fs/pstore/ram_core.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c > index 0306303..e126d9f 100644 > --- a/fs/pstore/ram_core.c > +++ b/fs/pstore/ram_core.c > @@ -337,7 +337,7 @@ static void *persistent_ram_vmap(phys_addr_t start, size_t size) > page_start = start - offset_in_page(start); > page_count = DIV_ROUND_UP(size + offset_in_page(start), PAGE_SIZE); > > - prot = pgprot_noncached(PAGE_KERNEL); > + prot = pgprot_writecombine(PAGE_KERNEL); Is this necessary? Won't pgprot_noncached already be normal memory?
> pages = kmalloc(sizeof(struct page *) * page_count, GFP_KERNEL); > if (!pages) { > @@ -364,7 +364,7 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size) > return NULL; > } > > - return ioremap(start, size); > + return ioremap_wc(start, size);
ioremap_wc corresponds to MT_DEVICE_WC, which is still device memory, so I don't see how this helps solve the problem in the commit message.
> } > > static int persistent_ram_buffer_map(phys_addr_t start, phys_addr_t size, > -- > 1.7.10.4 >
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