From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 6 Aug 2014 15:34:30 +0100 Subject: [PATCH v2 2/3] arm64: add helper functions to read I-cache attributes In-Reply-To: References: <1407230757-15305-1-git-send-email-ard.biesheuvel@linaro.org> <1407230757-15305-2-git-send-email-ard.biesheuvel@linaro.org> <20140806130026.GR25953@arm.com> Message-ID: <20140806143430.GU25953@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Aug 06, 2014 at 02:27:55PM +0100, Ard Biesheuvel wrote: > On 6 August 2014 15:17, Ard Biesheuvel wrote: > > On 6 August 2014 15:00, Will Deacon wrote: > >> On Tue, Aug 05, 2014 at 10:25:56AM +0100, Ard Biesheuvel wrote: > >>> This adds helper functions and #defines to to read the > >>> line size and the number of sets from the level 1 instruction cache. > >>> > >>> Signed-off-by: Ard Biesheuvel > >>> --- [...] > >>> +static inline __attribute_const__ u64 icache_get_ccsidr(void) > >>> +{ > >>> + u64 ccsidr; > >>> + > >>> + /* Select L1 I-cache and read its size ID register */ > >>> + asm("msr csselr_el1, %1; isb; mrs %0, ccsidr_el1" > >>> + : "=r"(ccsidr) : "r"(1L)); > >>> + return ccsidr; > >> > >> Is it worth having a WARN_ON(preemptible()) here? > >> > > > > Sure, why not. > > ... if it weren't for the fact that this triggers recursive header > inclusion hell > > CC kernel/bounds.s > In file included from /home/ard/linux-2.6/include/asm-generic/preempt.h:4:0, > from arch/arm64/include/generated/asm/preempt.h:1, > from /home/ard/linux-2.6/include/linux/preempt.h:18, > from /home/ard/linux-2.6/arch/arm64/include/asm/cachetype.h:21, [...] > i.e., linux/bug,h and linux/preempt.h already implicitly #include > cachetype.h, so including the former from the latter to import the > declaration of WARN_ON() and/or preemptible respectively produces this > error. Damn, that's a real shame. I'm always dubious about adding code like this which isn't obviously broken from preemptible context when you're just looking at the function name. Ho-hum. Will