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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Aug 2025 08:59:42.7807 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 92cd7bef-a7b0-4e7b-a5d6-08ddda47be6d X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: AM2PEPF0001C713.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS4PR08MB7710 +Ada Couprie Diaz > Hi Yeoreum, > > Thank you for pointing it! > > On 8/13/25 3:56 PM, Yeoreum Yun wrote: > > Hi Yunseong, > > > >> > >> | BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 > >> | in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20466, name: syz.0.1689 > >> | preempt_count: 1, expected: 0 > >> | RCU nest depth: 0, expected: 0 > >> | Preemption disabled at: > >> | [] debug_exception_enter arch/arm64/mm/fault.c:978 [inline] > >> | [] do_debug_exception+0x68/0x2fc arch/arm64/mm/fault.c:997 > >> | CPU: 0 UID: 0 PID: 20466 Comm: syz.0.1689 Not tainted 6.16.0-rc1-rt1-dirty #12 PREEMPT_RT > >> | Hardware name: QEMU KVM Virtual Machine, BIOS 2025.02-8 05/13/2025 > >> | Call trace: > >> | show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C) > >> | __dump_stack+0x30/0x40 lib/dump_stack.c:94 > >> | dump_stack_lvl+0x148/0x1d8 lib/dump_stack.c:120 > >> | dump_stack+0x1c/0x3c lib/dump_stack.c:129 > >> | __might_resched+0x2e4/0x52c kernel/sched/core.c:8800 > >> | __rt_spin_lock kernel/locking/spinlock_rt.c:48 [inline] > >> | rt_spin_lock+0xa8/0x1bc kernel/locking/spinlock_rt.c:57 > >> | spin_lock include/linux/spinlock_rt.h:44 [inline] > >> | force_sig_info_to_task+0x6c/0x4a8 kernel/signal.c:1302 > >> | force_sig_fault_to_task kernel/signal.c:1699 [inline] > >> | force_sig_fault+0xc4/0x110 kernel/signal.c:1704 > >> | arm64_force_sig_fault+0x6c/0x80 arch/arm64/kernel/traps.c:265 > >> | send_user_sigtrap arch/arm64/kernel/debug-monitors.c:237 [inline] > >> | single_step_handler+0x1f4/0x36c arch/arm64/kernel/debug-monitors.c:257 > >> | do_debug_exception+0x154/0x2fc arch/arm64/mm/fault.c:1002 > >> | el0_dbg+0x44/0x120 arch/arm64/kernel/entry-common.c:756 > >> | el0t_64_sync_handler+0x3c/0x108 arch/arm64/kernel/entry-common.c:832 > >> | el0t_64_sync+0x1ac/0x1b0 arch/arm64/kernel/entry.S:600 > >> > >> > >> It seems that commit eaff68b32861 ("arm64: entry: Add entry and exit functions > >> for debug exception") in 6.17-rc1, also present as 6fb44438a5e1 in mainline, > >> removed code that previously avoided sleeping context issues when handling > >> debug exceptions: > >> Link: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/arch/arm64/mm/fault.c?id=eaff68b3286116d499a3d4e513a36d772faba587 > > > > No. Her patch commit 31575e11ecf7 (arm64: debug: split brk64 exception entry) > > solves your splat since el0_brk64() doesn't call debug_exception_enter() > > by spliting el0/el1 brk64 entry exception entry. > > > > Formerly, el(0/1)_dbg() are handled in do_debug_exception() together > > and it calls debug_exception_enter() disabling preemption and this makes > > your splat while handling brk excepttion from el0. > > > > Do you think a fix is necessary if this issue also affects the LTS kernel > before 6.17-rc1? As far as I know, most production RT kernels are still > based on the existing LTS versions. IMHO, I think her patch should be backedported. [0]: https://lore.kernel.org/all/20250707114109.35672-1-ada.coupriediaz@arm.com/ Thanks. -- Sincerely, Yeoreum Yun