Christian Loehle f9b8d4dba8 sched: Fix sched_numa_find_nth_cpu() if mask offline ... commit 5ebf512f335053a42482ebff91e46c6dc156bf8c upstream. sched_numa_find_nth_cpu() uses a bsearch to look for the 'closest' CPU in sched_domains_numa_masks and given cpus mask. However they might not intersect if all CPUs in the cpus mask are offline. bsearch will return NULL in that case, bail out instead of dereferencing a bogus pointer. The previous behaviour lead to this bug when using maxcpus=4 on an rk3399 (LLLLbb) (i.e. booting with all big CPUs offline): [ 1.422922] Unable to handle kernel paging request at virtual address ffffff8000000000 [ 1.423635] Mem abort info: [ 1.423889] ESR = 0x0000000096000006 [ 1.424227] EC = 0x25: DABT (current EL), IL = 32 bits [ 1.424715] SET = 0, FnV = 0 [ 1.424995] EA = 0, S1PTW = 0 [ 1.425279] FSC = 0x06: level 2 translation fault [ 1.425735] Data abort info: [ 1.425998] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 [ 1.426499] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 1.426952] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 1.427428] swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000004a9f000 [ 1.428038] [ffffff8000000000] pgd=18000000f7fff403, p4d=18000000f7fff403, pud=18000000f7fff403, pmd=0000000000000000 [ 1.429014] Internal error: Oops: 0000000096000006 [#1] SMP [ 1.429525] Modules linked in: [ 1.429813] CPU: 3 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.17.0-rc4-dirty #343 PREEMPT [ 1.430559] Hardware name: Pine64 RockPro64 v2.1 (DT) [ 1.431012] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 1.431634] pc : sched_numa_find_nth_cpu+0x2a0/0x488 [ 1.432094] lr : sched_numa_find_nth_cpu+0x284/0x488 [ 1.432543] sp : ffffffc084e1b960 [ 1.432843] x29: ffffffc084e1b960 x28: ffffff80078a8800 x27: ffffffc0846eb1d0 [ 1.433495] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 [ 1.434144] x23: 0000000000000000 x22: fffffffffff7f093 x21: ffffffc081de6378 [ 1.434792] x20: 0000000000000000 x19: 0000000ffff7f093 x18: 00000000ffffffff [ 1.435441] x17: 3030303866666666 x16: 66663d736b73616d x15: ffffffc104e1b5b7 [ 1.436091] x14: 0000000000000000 x13: ffffffc084712860 x12: 0000000000000372 [ 1.436739] x11: 0000000000000126 x10: ffffffc08476a860 x9 : ffffffc084712860 [ 1.437389] x8 : 00000000ffffefff x7 : ffffffc08476a860 x6 : 0000000000000000 [ 1.438036] x5 : 000000000000bff4 x4 : 0000000000000000 x3 : 0000000000000000 [ 1.438683] x2 : 0000000000000000 x1 : ffffffc0846eb000 x0 : ffffff8000407b68 [ 1.439332] Call trace: [ 1.439559] sched_numa_find_nth_cpu+0x2a0/0x488 (P) [ 1.440016] smp_call_function_any+0xc8/0xd0 [ 1.440416] armv8_pmu_init+0x58/0x27c [ 1.440770] armv8_cortex_a72_pmu_init+0x20/0x2c [ 1.441199] arm_pmu_device_probe+0x1e4/0x5e8 [ 1.441603] armv8_pmu_device_probe+0x1c/0x28 [ 1.442007] platform_probe+0x5c/0xac [ 1.442347] really_probe+0xbc/0x298 [ 1.442683] __driver_probe_device+0x78/0x12c [ 1.443087] driver_probe_device+0xdc/0x160 [ 1.443475] __driver_attach+0x94/0x19c [ 1.443833] bus_for_each_dev+0x74/0xd4 [ 1.444190] driver_attach+0x24/0x30 [ 1.444525] bus_add_driver+0xe4/0x208 [ 1.444874] driver_register+0x60/0x128 [ 1.445233] __platform_driver_register+0x24/0x30 [ 1.445662] armv8_pmu_driver_init+0x28/0x4c [ 1.446059] do_one_initcall+0x44/0x25c [ 1.446416] kernel_init_freeable+0x1dc/0x3bc [ 1.446820] kernel_init+0x20/0x1d8 [ 1.447151] ret_from_fork+0x10/0x20 [ 1.447493] Code: 90022e21 f000e5f5 910de2b5 2a1703e2 (f8767803) [ 1.448040] ---[ end trace 0000000000000000 ]--- [ 1.448483] note: swapper/0[1] exited with preempt_count 1 [ 1.449047] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [ 1.449741] SMP: stopping secondary CPUs [ 1.450105] Kernel Offset: disabled [ 1.450419] CPU features: 0x000000,00080000,20002001,0400421b [ 1.450935] Memory Limit: none [ 1.451217] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]--- Yury: with the fix, the function returns cpu == nr_cpu_ids, and later in smp_call_function_any -> smp_call_function_single -> generic_exec_single we test the cpu for '>= nr_cpu_ids' and return -ENXIO. So everything is handled correctly. Fixes: cd7f55359c ("sched: add sched_numa_find_nth_cpu()") Cc: stable@vger.kernel.org Signed-off-by: Christian Loehle <christian.loehle@arm.com> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2025-09-09 18:56:26 +02:00
..
autogroup.c	sched/all: Change all BUG_ON() instances in the scheduler to WARN_ON_ONCE()	2022-08-12 11:25:10 +02:00
autogroup.h	sched/headers: Add header guard to kernel/sched/stats.h and kernel/sched/autogroup.h	2022-02-23 08:22:00 +01:00
build_policy.c	sched: Fix missing prototype warnings	2022-05-01 10:03:43 +02:00
build_utility.c	sched: Fix missing prototype warnings	2022-05-01 10:03:43 +02:00
clock.c	Locking changes for v6.5:	2023-06-27 14:14:30 -07:00
completion.c	sched: add a few helpers to wake up tasks on the current cpu	2023-07-17 16:08:08 -07:00
core_sched.c	sched: Rename task_running() to task_on_cpu()	2022-09-07 21:53:47 +02:00
core.c	freezer,sched: Use saved_state to reduce some spurious wakeups	2025-08-15 12:09:07 +02:00
cpuacct.c	Merge branch 'sched/fast-headers' into sched/core	2022-03-15 09:05:05 +01:00
cpudeadline.c	sched/topology: Consolidate and clean up access to a CPU's max compute capacity	2025-05-02 07:50:41 +02:00
cpudeadline.h
cpufreq_schedutil.c	sched/fair: Fix frequency selection for non-invariant case	2025-08-28 16:28:43 +02:00
cpufreq.c	sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there	2022-02-23 10:58:33 +01:00
cpupri.c	sched/rt: Fix live lock between select_fallback_rq() and RT push	2023-09-28 22:58:13 +02:00
cpupri.h
cputime.c	sched/cputime: Fix mul_u64_u64_div_u64() precision for cputime	2024-08-14 13:58:47 +02:00
deadline.c	sched/topology: Consolidate and clean up access to a CPU's max compute capacity	2025-05-02 07:50:41 +02:00
debug.c	sched/debug: Provide slice length for fair tasks	2025-03-22 12:50:40 -07:00
fair.c	sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails	2025-08-28 16:28:21 +02:00
features.h	sched/eevdf: Curb wakeup-preemption	2023-08-17 17:07:07 +02:00
idle.c	sched/fair: Rename check_preempt_curr() to wakeup_preempt()	2024-12-14 20:00:18 +01:00
isolation.c	sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU	2024-06-12 11:11:24 +02:00
loadavg.c	sched: Change nr_uninterruptible type to unsigned long	2025-07-24 08:53:20 +02:00
Makefile	sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there	2022-02-23 10:58:33 +01:00
membarrier.c	sched/membarrier: reduce the ability to hammer on sys_membarrier	2024-02-23 09:25:27 +01:00
pelt.c	sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there	2022-02-23 10:58:33 +01:00
pelt.h	sched/fair: Decay task PELT values during wakeup migration	2022-06-28 09:17:46 +02:00
psi.c	sched/psi: Fix psi_seq initialization	2025-08-15 12:09:00 +02:00
rt.c	sched/topology: Consolidate and clean up access to a CPU's max compute capacity	2025-05-02 07:50:41 +02:00
sched-pelt.h
sched.h	sched: Change nr_uninterruptible type to unsigned long	2025-07-24 08:53:20 +02:00
smp.h	sched, smp: Trace smp callback causing an IPI	2023-03-24 11:01:29 +01:00
stats.c	profiling: remove profile=sleep support	2024-08-14 13:58:47 +02:00
stats.h	sched: Move psi_account_irqtime() out of update_rq_clock_task() hotpath	2024-07-18 13:21:25 +02:00
stop_task.c	sched: Unify runtime accounting across classes	2024-12-14 20:00:19 +01:00
swait.c	sched: add a few helpers to wake up tasks on the current cpu	2023-07-17 16:08:08 -07:00
topology.c	sched: Fix sched_numa_find_nth_cpu() if mask offline	2025-09-09 18:56:26 +02:00
wait_bit.c	wait_on_bit: add an acquire memory barrier	2022-08-26 09:30:25 -07:00
wait.c	sched: add a few helpers to wake up tasks on the current cpu	2023-07-17 16:08:08 -07:00