Hi Linus,
Your final commit 596ff4a09b898179 ("cpumask: re-introduce
constant-sized cpumask optimizations") in v6.3-rc1 introduced a
regression. During Debian userspace startup, the kernel crashes with:
Alignment trap: not handling instruction e1931f9f at [<c015f0b4>]
8<--- cut here ---
Unhandled fault: alignment exception (0x001) at 0xc0c5b701
[c0c5b701] *pgd=40c1141e(bad)
Internal error: : 1 [#1] SMP ARM
CPU: 0 PID: 1 Comm: systemd Not tainted 6.3.0-rc1-shmobile #1519
Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
PC is at arch_spin_lock+0x10/0x48
LR is at arch_spin_lock+0xc/0x48
pc : [<c015f0b8>] lr : [<c015f0b4>] psr: 80060093
sp : f0815e48 ip : c0c5b700 fp : c0d04e08
r10: c0d05b34 r9 : c0e5c284 r8 : c10ad140
r7 : f0815e84 r6 : 00000008 r5 : c0c5b701 r4 : f0815e84
r3 : c0c5b701 r2 : c0858678 r1 : 40060013 r0 : c0c5b701
Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none
Control: 10c5387d Table: 4204c06a DAC: 00000051
Register r0 information: non-slab/vmalloc memory
Register r1 information: non-paged memory
Register r2 information: non-slab/vmalloc memory
Register r3 information: non-slab/vmalloc memory
Register r4 information: 2-page vmalloc region starting at
0xf0814000 allocated at kernel_clone+0xa0/0x258
Register r5 information: non-slab/vmalloc memory
Register r6 information: non-paged memory
Register r7 information: 2-page vmalloc region starting at
0xf0814000 allocated at kernel_clone+0xa0/0x258
Register r8 information: slab task_struct start c10ad140 pointer
offset 0 size 2176
Register r9 information: non-slab/vmalloc memory
Register r10 information: non-slab/vmalloc memory
Register r11 information: non-slab/vmalloc memory
Register r12 information: non-slab/vmalloc memory
Process systemd (pid: 1, stack limit = 0x(ptrval))
Stack: (0xf0815e48 to 0xf0816000)
5e40: f0815e84 c0186694 40060013 96063d9c
f0815e80 00000008
5e60: 00000002 c08584a4 00000000 96063d9c 00000000 04a183ac
00000003 00000001
5e80: 04a183ac 00000122 00000000 ffff8dd8 c0858678 06040001
00000001 00000002
5ea0: f7e1016b 00000007 c2143015 004c6000 00000000 c1d05000
c12c20d0 00000101
5ec0: 00000000 00000000 00000000 0000007a 00000038 00000000
00000000 96063d9c
5ee0: f0815ee4 c0e5c284 f0815f18 c22ad240 f0815f78 be847850
c10ad140 00000003
5f00: b6e61130 c0445328 00000000 00000010 c22ad240 c024ab18
01000006 00000000
5f20: 00000010 be847850 00000000 00000000 c22ad240 00000000
00000000 00000000
5f40: 00000000 00000000 00000000 00004004 00000000 00000000
00000001 96063d9c
5f60: c22ad240 be847850 f0815f78 f0815f84 00000010 c024af94
00000000 00000000
5f80: 00000000 c22ad240 00000000 96063d9c 00000074 be847850
00000000 00000003
5fa0: c01002c4 c0100060 00000074 be847850 0000000c be847850
00000010 00000000
5fc0: 00000074 be847850 00000000 00000003 00000001 00000001
00000001 b6e61130
5fe0: 00000003 be8477c0 b6ef152f b6e7a746 60060030 0000000c
00000000 00000000
arch_spin_lock from add_timer_on+0xe8/0x124
add_timer_on from try_to_generate_entropy+0x1f4/0x250
try_to_generate_entropy from urandom_read_iter+0x2c/0xc8
urandom_read_iter from vfs_read+0x124/0x178
vfs_read from ksys_read+0x74/0xc8
ksys_read from ret_fast_syscall+0x0/0x54
Exception stack(0xf0815fa8 to 0xf0815ff0)
5fa0: 00000074 be847850 0000000c be847850
00000010 00000000
5fc0: 00000074 be847850 00000000 00000003 00000001 00000001
00000001 b6e61130
5fe0: 00000003 be8477c0 b6ef152f b6e7a746
Code: e92d4010 e1a03000 ebfffff7 e1931f9f (e2812801)
---[ end trace 0000000000000000 ]---
note: systemd[1] exited with irqs disabled
| #define for_each_cpu_wrap(cpu, mask, start) \
| - for_each_set_bit_wrap(cpu, cpumask_bits(mask),
nr_cpumask_bits, start)
| + for_each_set_bit_wrap(cpu, cpumask_bits(mask),
small_cpumask_bits, start)
Presumably using small_cpumask_bits instead of nr_cpu_ids accesses
some uninitialized array members?
NR_CPUS = 8
small_cpumask_bits = 8
nr_cpu_ids = 2
A similar kernel on an arm64 system that does have 8 CPU cores works fine.
On an arm64 system with 2 CPU cores, it crashes in a similar way.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
