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Thu, 18 Jan 2024 20:42:27 -0800 (PST) Received: from localhost ([2601:344:8301:57f0:b45f:9648:c2e:2e36]) by smtp.gmail.com with ESMTPSA id b6-20020a0dd906000000b005f941afab71sm21362ywe.30.2024.01.18.20.42.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jan 2024 20:42:26 -0800 (PST) Date: Thu, 18 Jan 2024 20:42:25 -0800 From: Yury Norov To: Huang Shijie Cc: gregkh@linuxfoundation.org, patches@amperecomputing.com, rafael@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, kuba@kernel.org, vschneid@redhat.com, mingo@kernel.org, akpm@linux-foundation.org, vbabka@suse.cz, rppt@kernel.org, tglx@linutronix.de, jpoimboe@kernel.org, ndesaulniers@google.com, mikelley@microsoft.com, mhiramat@kernel.org, arnd@arndb.de, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, chenhuacai@kernel.org, jiaxun.yang@flygoat.com, linux-mips@vger.kernel.org, cl@os.amperecomputing.com Subject: Re: [PATCH] NUMA: Early use of cpu_to_node() returns 0 instead of the correct node id Message-ID: References: <20240119033227.14113-1-shijie@os.amperecomputing.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240119033227.14113-1-shijie@os.amperecomputing.com> On Fri, Jan 19, 2024 at 11:32:27AM +0800, Huang Shijie wrote: > hZ7bkEvc+Z19RHkS/HVG3KMg > X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM8PR01MB7144 > Status: O > Content-Length: 3779 > Lines: 126 > > During the kernel booting, the generic cpu_to_node() is called too early in > arm64, powerpc and riscv when CONFIG_NUMA is enabled. > > There are at least four places in the common code where > the generic cpu_to_node() is called before it is initialized: > 1.) early_trace_init() in kernel/trace/trace.c > 2.) sched_init() in kernel/sched/core.c > 3.) init_sched_fair_class() in kernel/sched/fair.c > 4.) workqueue_init_early() in kernel/workqueue.c > > In order to fix the bug, the patch changes generic cpu_to_node to > function pointer, and export it for kernel modules. > Introduce smp_prepare_boot_cpu_start() to wrap the original > smp_prepare_boot_cpu(), and set cpu_to_node with early_cpu_to_node. > Introduce smp_prepare_cpus_done() to wrap the original smp_prepare_cpus(), > and set the cpu_to_node to formal _cpu_to_node(). This adds another level of indirection, I think. Currently cpu_to_node is a simple inliner. After the patch it would be a real function with all the associate overhead. Can you share a bloat-o-meter output here? Regardless, I don't think that the approach is correct. As per your description, some initialization functions erroneously call cpu_to_node() instead of early_cpu_to_node() which exists specifically for that case. If the above correct, it's clearly a caller problem, and the fix is to simply switch all those callers to use early version. I would also initialize the numa_node with NUMA_NO_NODE at declaration, so that if someone calls cpu_to_node() before the variable is properly initialized at runtime, he'll get NO_NODE, which is obviously an error. Thanks, Yury > Signed-off-by: Huang Shijie > --- > drivers/base/arch_numa.c | 11 +++++++++++ > include/linux/topology.h | 6 ++---- > init/main.c | 29 +++++++++++++++++++++++++++-- > 3 files changed, 40 insertions(+), 6 deletions(-) > > diff --git a/drivers/base/arch_numa.c b/drivers/base/arch_numa.c > index 5b59d133b6af..867a477fa975 100644 > --- a/drivers/base/arch_numa.c > +++ b/drivers/base/arch_numa.c > @@ -61,6 +61,17 @@ EXPORT_SYMBOL(cpumask_of_node); > > #endif > > +#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID > +#ifndef cpu_to_node > +int _cpu_to_node(int cpu) > +{ > + return per_cpu(numa_node, cpu); > +} > +int (*cpu_to_node)(int cpu); > +EXPORT_SYMBOL(cpu_to_node); > +#endif > +#endif > + > static void numa_update_cpu(unsigned int cpu, bool remove) > { > int nid = cpu_to_node(cpu); > diff --git a/include/linux/topology.h b/include/linux/topology.h > index 52f5850730b3..e7ce2bae11dd 100644 > --- a/include/linux/topology.h > +++ b/include/linux/topology.h > @@ -91,10 +91,8 @@ static inline int numa_node_id(void) > #endif > > #ifndef cpu_to_node > -static inline int cpu_to_node(int cpu) > -{ > - return per_cpu(numa_node, cpu); > -} > +extern int (*cpu_to_node)(int cpu); > +extern int _cpu_to_node(int cpu); > #endif > > #ifndef set_numa_node > diff --git a/init/main.c b/init/main.c > index e24b0780fdff..b142e9c51161 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -870,6 +870,18 @@ static void __init print_unknown_bootoptions(void) > memblock_free(unknown_options, len); > } > > +static void __init smp_prepare_boot_cpu_start(void) > +{ > + smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ > + > +#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID > +#ifndef cpu_to_node > + /* The early_cpu_to_node should be ready now. */ > + cpu_to_node = early_cpu_to_node; > +#endif > +#endif > +} > + > asmlinkage __visible __init __no_sanitize_address __noreturn __no_stack_protector > void start_kernel(void) > { > @@ -899,7 +911,7 @@ void start_kernel(void) > setup_command_line(command_line); > setup_nr_cpu_ids(); > setup_per_cpu_areas(); > - smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ > + smp_prepare_boot_cpu_start(); > boot_cpu_hotplug_init(); > > pr_notice("Kernel command line: %s\n", saved_command_line); > @@ -1519,6 +1531,19 @@ void __init console_on_rootfs(void) > fput(file); > } > > +static void __init smp_prepare_cpus_done(unsigned int setup_max_cpus) > +{ > + /* Different ARCHs may override smp_prepare_cpus() */ > + smp_prepare_cpus(setup_max_cpus); > + > +#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID > +#ifndef cpu_to_node > + /* Change to the formal function. */ > + cpu_to_node = _cpu_to_node; > +#endif > +#endif > +} > + > static noinline void __init kernel_init_freeable(void) > { > /* Now the scheduler is fully set up and can do blocking allocations */ > @@ -1531,7 +1556,7 @@ static noinline void __init kernel_init_freeable(void) > > cad_pid = get_pid(t