(0) We list the ARCHs which support the NUMA:
arm64, loongarch, powerpc, riscv,
sparc, mips, s390, x86,
(1) Some ARCHs in (0) override the generic cpu_to_node(), such as:
sparc, mips, s390, x86.
Since these ARCHs have their own cpu_to_node(), we do not care
about them.
(2) The ARCHs enable NUMA and use the generic cpu_to_node.
From (0) and (1), we can know that four ARCHs support NUMA and
use the generic cpu_to_node:
arm64, loongarch, powerpc, riscv,
The generic cpu_to_node depends on percpu "numa_node".
(2.1) The loongarch sets "numa_node" in:
start_kernel --> smp_prepare_boot_cpu()
(2.2) The arm64, powerpc, riscv set "numa_node" in:
start_kernel --> arch_call_rest_init() --> rest_init()
--> kernel_init() --> kernel_init_freeable()
--> smp_prepare_cpus()
(2.3) The first place calling the cpu_to_node() is early_trace_init():
start_kernel --> early_trace_init()--> __ring_buffer_alloc()
--> rb_allocate_cpu_buffer()
(2.4) So it safe for loongarch. But for arm64, powerpc and riscv,
there are at least four places in the common code where
the cpu_to_node() is called before it is initialized:
a.) early_trace_init() in kernel/trace/trace.c
b.) sched_init() in kernel/sched/core.c
c.) init_sched_fair_class() in kernel/sched/fair.c
d.) workqueue_init_early() in kernel/workqueue.c
(3) In order to fix the issue, the patch refactors the generic cpu_to_node:
(3.1) change cpu_to_node to function pointer,
and export it for kernel modules.
(3.2) introduce _cpu_to_node() which is the original cpu_to_node().
(3.3) introduce smp_prepare_boot_cpu_start() to wrap the original
smp_prepare_boot_cpu(), and set cpu_to_node with
early_cpu_to_node which works fine for arm64, powerpc,
riscv and loongarch.
(3.4) introduce smp_prepare_cpus_done() to wrap the original
smp_prepare_cpus().
The "numa_node" is ready after smp_prepare_cpus(),
then set cpu_to_node with _cpu_to_node().
Signed-off-by: Huang Shijie <shijie@xxxxxxxxxxxxxxxxxxxxxx>
---
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(task_pid(current));
- smp_prepare_cpus(setup_max_cpus);
+ smp_prepare_cpus_done(setup_max_cpus);
workqueue_init();
--
2.40.1
