linux-kernel - Re: [PATCH 6.1 0/6] fix invalid sleeping in detect_cache

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Message-ID: <2025101509-bucktooth-reawake-5176@gregkh>
Date: Wed, 15 Oct 2025 10:43:01 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Wen Yang <wen.yang@...ux.dev>, Jon Hunter <jonathanh@...dia.com>
Cc: stable@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6.1 0/6] fix invalid sleeping in detect_cache_attributes()

On Wed, Oct 01, 2025 at 01:27:25AM +0800, Wen Yang wrote:
> 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@arm.com/
> 
> We also encountered the same issue on 6.1 stable branch,  and need to backport this series.
> 
> Pierre Gondois (6):
>   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

This series seems to have broken existing systems, as reported here:
	https://lore.kernel.org/r/046f08cb-0610-48c9-af24-4804367df177@nvidia.com

so I'm going to drop it from the queue at this point in time.  Please
work to resolve this before resubmitting it.

thanks,

greg k-h