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' as the code is executed with preemption and interrupts disabled:
| 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
Pierre fixed this issue in the upstream 6.3 and the original series is follows: https://lore.kernel.org/all/167404285593.885445.6219705651301997538.b4-ty@ar...
We also encountered the same issue on 6.1 stable branch, and need to backport this series: cacheinfo: Use RISC-V's init_cache_level() as generic OF implementation cacheinfo: Return error code in init_of_cache_level() cacheinfo: Check 'cache-unified' property to count cache leaves ACPI: PPTT: Remove acpi_find_cache_levels() ACPI: PPTT: Update acpi_find_last_cache_level() to acpi_get_cache_info() arch_topology: Build cacheinfo from primary CPU
And there was a non-trivial number of follow-on fixes for patches in this series, as pointed out by Greg in the 6.1.156-RC1 review: cacheinfo: Initialize variables in fetch_cache_info() cacheinfo: Fix LLC is not exported through sysfs drivers: base: cacheinfo: Update cpu_map_populated during CPU Hotplug
Finally, Jon discovered an issue in the Tegra platform caused by these patches: https://lore.kernel.org/all/046f08cb-0610-48c9-af24-4804367df177@nvidia.com/ So we also need to backport the following patch: arm64: tegra: Update cache properties
K Prateek Nayak (1): drivers: base: cacheinfo: Update cpu_map_populated during CPU Hotplug
Pierre Gondois (8): cacheinfo: Use RISC-V's init_cache_level() as generic OF implementation cacheinfo: Return error code in init_of_cache_level() cacheinfo: Check 'cache-unified' property to count cache leaves ACPI: PPTT: Remove acpi_find_cache_levels() ACPI: PPTT: Update acpi_find_last_cache_level() to acpi_get_cache_info() arch_topology: Build cacheinfo from primary CPU cacheinfo: Initialize variables in fetch_cache_info() arm64: tegra: Update cache properties
Yicong Yang (1): cacheinfo: Fix LLC is not exported through sysfs
arch/arm64/boot/dts/nvidia/tegra194.dtsi | 15 +++ arch/arm64/boot/dts/nvidia/tegra210.dtsi | 1 + arch/arm64/boot/dts/nvidia/tegra234.dtsi | 33 +++++ arch/arm64/kernel/cacheinfo.c | 11 +- arch/riscv/kernel/cacheinfo.c | 42 ------ drivers/acpi/pptt.c | 93 ++++++++------ drivers/base/arch_topology.c | 12 +- drivers/base/cacheinfo.c | 156 +++++++++++++++++++---- include/linux/cacheinfo.h | 11 +- 9 files changed, 262 insertions(+), 112 deletions(-)