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Message-Id: <20250926174658.6546-1-wen.yang@linux.dev>
Date: Sat, 27 Sep 2025 01:46:58 +0800
From: Wen Yang <wen.yang@...ux.dev>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org,
Pierre Gondois <pierre.gondois@....com>,
Sudeep Holla <sudeep.holla@....com>,
Palmer Dabbelt <palmer@...osinc.com>,
stable@...r.kernel.org,
Wen Yang <wen.yang@...ux.dev>
Subject: [PATCH 6.1] arch_topology: Build cacheinfo from primary CPU
From: Pierre Gondois <pierre.gondois@....com>
commit 5944ce092b97caed5d86d961e963b883b5c44ee2 upstream.
commit 3fcbf1c77d08 ("arch_topology: Fix cache attributes detection
in the CPU hotplug path")
adds a call to detect_cache_attributes() to populate the cacheinfo
before updating the siblings mask. detect_cache_attributes() allocates
memory and can take the PPTT mutex (on ACPI platforms). On PREEMPT_RT
kernels, on secondary CPUs, this triggers a:
'BUG: sleeping function called from invalid context' [1]
as the code is executed with preemption and interrupts disabled.
The primary CPU was previously storing the cache information using
the now removed (struct cpu_topology).llc_id:
commit 5b8dc787ce4a ("arch_topology: Drop LLC identifier stash from
the CPU topology")
allocate_cache_info() tries to build the cacheinfo from the primary
CPU prior secondary CPUs boot, if the DT/ACPI description
contains cache information.
If allocate_cache_info() fails, then fallback to the current state
for the cacheinfo allocation. [1] will be triggered in such case.
When unplugging a CPU, the cacheinfo memory cannot be freed. If it
was, then the memory would be allocated early by the re-plugged
CPU and would trigger [1].
Note that populate_cache_leaves() might be called multiple times
due to populate_leaves being moved up. This is required since
detect_cache_attributes() might be called with per_cpu_cacheinfo(cpu)
being allocated but not populated.
[1]:
| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
| in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/111
| preempt_count: 1, expected: 0
| RCU nest depth: 1, expected: 1
| 3 locks held by swapper/111/0:
| #0: (&pcp->lock){+.+.}-{3:3}, at: get_page_from_freelist+0x218/0x12c8
| #1: (rcu_read_lock){....}-{1:3}, at: rt_spin_trylock+0x48/0xf0
| #2: (&zone->lock){+.+.}-{3:3}, at: rmqueue_bulk+0x64/0xa80
| irq event stamp: 0
| hardirqs last enabled at (0): 0x0
| hardirqs last disabled at (0): copy_process+0x5dc/0x1ab8
| softirqs last enabled at (0): copy_process+0x5dc/0x1ab8
| softirqs last disabled at (0): 0x0
| Preemption disabled at:
| migrate_enable+0x30/0x130
| CPU: 111 PID: 0 Comm: swapper/111 Tainted: G W 6.0.0-rc4-rt6-[...]
| Call trace:
| __kmalloc+0xbc/0x1e8
| detect_cache_attributes+0x2d4/0x5f0
| update_siblings_masks+0x30/0x368
| store_cpu_topology+0x78/0xb8
| secondary_start_kernel+0xd0/0x198
| __secondary_switched+0xb0/0xb4
Signed-off-by: Pierre Gondois <pierre.gondois@....com>
Reviewed-by: Sudeep Holla <sudeep.holla@....com>
Acked-by: Palmer Dabbelt <palmer@...osinc.com>
Link: https://lore.kernel.org/r/20230104183033.755668-7-pierre.gondois@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
Cc: <stable@...r.kernel.org> # 6.1.x: c3719bd:cacheinfo: Use RISC-V's init_cache_level() as generic OF implementation
Cc: <stable@...r.kernel.org> # 6.1.x: 8844c3d:cacheinfo: Return error code in init_of_cache_level(
Cc: <stable@...r.kernel.org> # 6.1.x: de0df44:cacheinfo: Check 'cache-unified' property to count cache leaves
Cc: <stable@...r.kernel.org> # 6.1.x: fa4d566:ACPI: PPTT: Remove acpi_find_cache_levels()
Cc: <stable@...r.kernel.org> # 6.1.x: bd50036:ACPI: PPTT: Update acpi_find_last_cache_level() to acpi_get_cache_info(
Cc: <stable@...r.kernel.org> # 6.1.x
Signed-off-by: Wen Yang <wen.yang@...ux.dev>
---
arch/riscv/kernel/cacheinfo.c | 5 ---
drivers/base/arch_topology.c | 12 +++++-
drivers/base/cacheinfo.c | 71 ++++++++++++++++++++++++++---------
include/linux/cacheinfo.h | 1 +
4 files changed, 65 insertions(+), 24 deletions(-)
diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
index 440a3df5944c..3a13113f1b29 100644
--- a/arch/riscv/kernel/cacheinfo.c
+++ b/arch/riscv/kernel/cacheinfo.c
@@ -113,11 +113,6 @@ static void fill_cacheinfo(struct cacheinfo **this_leaf,
}
}
-int init_cache_level(unsigned int cpu)
-{
- return init_of_cache_level(cpu);
-}
-
int populate_cache_leaves(unsigned int cpu)
{
struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index e7d6e6657ffa..b1c1dd38ab01 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -736,7 +736,7 @@ void update_siblings_masks(unsigned int cpuid)
ret = detect_cache_attributes(cpuid);
if (ret && ret != -ENOENT)
- pr_info("Early cacheinfo failed, ret = %d\n", ret);
+ pr_info("Early cacheinfo allocation failed, ret = %d\n", ret);
/* update core and thread sibling masks */
for_each_online_cpu(cpu) {
@@ -825,7 +825,7 @@ __weak int __init parse_acpi_topology(void)
#if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
void __init init_cpu_topology(void)
{
- int ret;
+ int cpu, ret;
reset_cpu_topology();
ret = parse_acpi_topology();
@@ -840,6 +840,14 @@ void __init init_cpu_topology(void)
reset_cpu_topology();
return;
}
+
+ for_each_possible_cpu(cpu) {
+ ret = fetch_cache_info(cpu);
+ if (ret) {
+ pr_err("Early cacheinfo failed, ret = %d\n", ret);
+ break;
+ }
+ }
}
void store_cpu_topology(unsigned int cpuid)
diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index ab99b0f0d010..cd943d06d074 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -412,10 +412,6 @@ static void free_cache_attributes(unsigned int cpu)
return;
cache_shared_cpu_map_remove(cpu);
-
- kfree(per_cpu_cacheinfo(cpu));
- per_cpu_cacheinfo(cpu) = NULL;
- cache_leaves(cpu) = 0;
}
int __weak init_cache_level(unsigned int cpu)
@@ -428,29 +424,71 @@ int __weak populate_cache_leaves(unsigned int cpu)
return -ENOENT;
}
+static inline
+int allocate_cache_info(int cpu)
+{
+ per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
+ sizeof(struct cacheinfo), GFP_ATOMIC);
+ if (!per_cpu_cacheinfo(cpu)) {
+ cache_leaves(cpu) = 0;
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+int fetch_cache_info(unsigned int cpu)
+{
+ struct cpu_cacheinfo *this_cpu_ci;
+ unsigned int levels, split_levels;
+ int ret;
+
+ if (acpi_disabled) {
+ ret = init_of_cache_level(cpu);
+ if (ret < 0)
+ return ret;
+ } else {
+ ret = acpi_get_cache_info(cpu, &levels, &split_levels);
+ if (ret < 0)
+ return ret;
+
+ this_cpu_ci = get_cpu_cacheinfo(cpu);
+ this_cpu_ci->num_levels = levels;
+ /*
+ * This assumes that:
+ * - there cannot be any split caches (data/instruction)
+ * above a unified cache
+ * - data/instruction caches come by pair
+ */
+ this_cpu_ci->num_leaves = levels + split_levels;
+ }
+ if (!cache_leaves(cpu))
+ return -ENOENT;
+
+ return allocate_cache_info(cpu);
+}
+
int detect_cache_attributes(unsigned int cpu)
{
int ret;
- /* Since early detection of the cacheinfo is allowed via this
- * function and this also gets called as CPU hotplug callbacks via
- * cacheinfo_cpu_online, the initialisation can be skipped and only
- * CPU maps can be updated as the CPU online status would be update
- * if called via cacheinfo_cpu_online path.
+ /* Since early initialization/allocation of the cacheinfo is allowed
+ * via fetch_cache_info() and this also gets called as CPU hotplug
+ * callbacks via cacheinfo_cpu_online, the init/alloc can be skipped
+ * as it will happen only once (the cacheinfo memory is never freed).
+ * Just populate the cacheinfo.
*/
if (per_cpu_cacheinfo(cpu))
- goto update_cpu_map;
+ goto populate_leaves;
if (init_cache_level(cpu) || !cache_leaves(cpu))
return -ENOENT;
- per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),
- sizeof(struct cacheinfo), GFP_ATOMIC);
- if (per_cpu_cacheinfo(cpu) == NULL) {
- cache_leaves(cpu) = 0;
- return -ENOMEM;
- }
+ ret = allocate_cache_info(cpu);
+ if (ret)
+ return ret;
+populate_leaves:
/*
* populate_cache_leaves() may completely setup the cache leaves and
* shared_cpu_map or it may leave it partially setup.
@@ -459,7 +497,6 @@ int detect_cache_attributes(unsigned int cpu)
if (ret)
goto free_ci;
-update_cpu_map:
/*
* For systems using DT for cache hierarchy, fw_token
* and shared_cpu_map will be set up here only if they are
diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
index 00d8e7f9d1c6..dfef57077cd0 100644
--- a/include/linux/cacheinfo.h
+++ b/include/linux/cacheinfo.h
@@ -85,6 +85,7 @@ int populate_cache_leaves(unsigned int cpu);
int cache_setup_acpi(unsigned int cpu);
bool last_level_cache_is_valid(unsigned int cpu);
bool last_level_cache_is_shared(unsigned int cpu_x, unsigned int cpu_y);
+int fetch_cache_info(unsigned int cpu);
int detect_cache_attributes(unsigned int cpu);
#ifndef CONFIG_ACPI_PPTT
/*
--
2.25.1
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