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Tue, 25 Sep 2018 14:15:35 +0200 (CEST) Received: from PO15451 (unknown [192.168.232.3]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 28AF98B7C8; Tue, 25 Sep 2018 14:15:34 +0200 (CEST) Subject: Re: [RFC PATCH v1 1/9] timer: fix circular header dependency To: Mark Rutland Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , aneesh.kumar@linux.vnet.ibm.com, npiggin@gmail.com, Thomas Gleixner , Alexander Viro , John Stultz , Stephen Boyd , linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <72d3e8c38f729dc22cb3235319b72f96190e01ee.1537802981.git.christophe.leroy@c-s.fr> <5c9530da-f5c8-e0b2-61ab-294a0da7f3fc@c-s.fr> <20180925121104.zrz4m45sbnt5h2ht@lakrids.cambridge.arm.com> From: Christophe LEROY Message-ID: Date: Tue, 25 Sep 2018 14:15:34 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180925121104.zrz4m45sbnt5h2ht@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 25/09/2018 à 14:11, Mark Rutland a écrit : > On Tue, Sep 25, 2018 at 07:34:15AM +0200, Christophe LEROY wrote: >> >> >> Le 24/09/2018 à 17:52, Christophe Leroy a écrit : >>> When switching powerpc to CONFIG_THREAD_INFO_IN_TASK, include/sched.h >>> has to be included in asm/smp.h for the following change, in order >>> to avoid uncomplete definition of task_struct: >>> >>> -#define raw_smp_processor_id() (current_thread_info()->cpu) >>> +#define raw_smp_processor_id() (current->cpu) >>> >>> But this generates the following compilation error, due to circular >>> header dependency. >>> >>> CC kernel/time/alarmtimer.o >>> In file included from ./arch/powerpc/include/asm/smp.h:31, >>> from ./include/linux/smp.h:64, >>> from ./include/linux/percpu.h:7, >>> from ./include/linux/hrtimer.h:22, >>> from kernel/time/alarmtimer.c:19: >>> ./include/linux/sched.h:558:19: error: field 'dl_timer' has incomplete type >>> struct hrtimer dl_timer; >>> ^~~~~~~~ >>> ./include/linux/sched.h:567:17: error: field 'inactive_timer' has incomplete type >>> struct hrtimer inactive_timer; >>> ^~~~~~~~~~~~~~ >>> make[1]: *** [kernel/time/alarmtimer.o] Error 1 >>> make: *** [kernel/time/alarmtimer.o] Error 2 >>> >>> CC fs/timerfd.o >>> In file included from ./arch/powerpc/include/asm/smp.h:31, >>> from ./include/linux/smp.h:64, >>> from ./include/linux/percpu.h:7, >>> from ./include/linux/hrtimer.h:22, >>> from ./include/linux/alarmtimer.h:6, >>> from fs/timerfd.c:12: >>> ./include/linux/sched.h:558:19: error: field 'dl_timer' has incomplete type >>> struct hrtimer dl_timer; >>> ^~~~~~~~ >>> ./include/linux/sched.h:567:17: error: field 'inactive_timer' has incomplete type >>> struct hrtimer inactive_timer; >>> ^~~~~~~~~~~~~~ >>> make[1]: *** [fs/timerfd.o] Error 1 >>> make: *** [fs/timerfd.o] Error 2 >>> >>> This patch fixes it by including linux/hrtimer.h after linux/sched.h >>> >>> Signed-off-by: Christophe Leroy >>> --- >>> Should it be fixed in powerpc instead ? In that case, how ? Any idea ? >> >> >> Looks like there are several other places where the problem occurs, so it >> has to be fixed in the powerpc headers instead. >> >> Seems like RISC arch faced the same issue, and fixed it the following way: >> >> /* >> * This is particularly ugly: it appears we can't actually get the >> definition >> * of task_struct here, but we need access to the CPU this task is running >> on. >> * Instead of using C we're using asm-offsets.h to get the current processor >> * ID. >> */ >> #define raw_smp_processor_id() (*((int*)((char*)get_current() + >> TASK_TI_CPU))) >> >> >> Unless someone has a better idea, I'll fixed it that way. > > To solve this on arm64 we made the cpu number a percpu variable; see > commit: > > 57c82954e77fa12c ("arm64: make cpu number a percpu variable") Thanks, I'll have a look > IIUC, you could do that by placing it in paca_struct. By the way, it is already in PACA struct for PPC64. The issue is with PPC32, up to now it was in current_thread_info: #ifdef CONFIG_PPC64 #define raw_smp_processor_id() (local_paca->paca_index) #define hard_smp_processor_id() (get_paca()->hw_cpu_id) #else /* 32-bit */ extern int smp_hw_index[]; #define raw_smp_processor_id() (current_thread_info()->cpu) #define hard_smp_processor_id() (smp_hw_index[smp_processor_id()]) [..] #endif Christophe