From: Daniel Dragomir <daniel.drago...@windriver.com>
This error was introduced in commit d02636e8d3 ("Merge branch
'v4.19/standard/base' into v4.19/standard/preempt-rt/base")
when a merge conflict has overwrited the changes from commit
373491f1f4 ("sched/core: Fix illegal RCU from offline CPUs").
This BUG occurs when running cpu_hotplug_stress testcase from
KTS or when stressing one CPU by switching it online/offline
(echo 0 and 1 in /sys/devices/system/cpu/cpu0/online).
kernel BUG at kernel/fork.c:633!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:
Process sh (pid: 2016, stack limit = 0x00000000ca5ad524)
CPU: 10 PID: 2016 Comm: sh Not tainted 4.19.131-rt30 axxia_gen2
Hardware name: AXM56xx Victoria (DT)
pstate: 60000005 (nZCv daif -PAN -UAO)
pc : __mmdrop+0x120/0x138
lr : finish_cpu+0x68/0x70
sp : ffffff8012153a40
x29: ffffff8012153a40 x28: ffffffc07b389e00
x27: 0000000000000000 x26: 000000407610f000
x25: ffffffc07ee62ee0 x24: 0000000000000000
x23: ffffff80080dfc20 x22: ffffff8008d9a9d8
x21: ffffff8008d53ee0 x20: 0000000000000055
x19: ffffff8008dc1b58 x18: 0000000000000001
x17: 0000000000000000 x16: 0000000000000000
x15: ffffffffffffffff x14: ffffff8008d89688
x13: ffffff8088d918d7 x12: ffffff8008d918e0
x11: ffffff8008da4000 x10: ffffff8012153a00
x9 : 00000000ffffffd0 x8 : ffffff80121539d0
x7 : 0000000000000000 x6 : 0000000000000001
x5 : 00000000fffffffb x4 : 0000000000000030
x3 : 0000000000000030 x2 : ffffff8008dc1b58
x1 : ffffff8008dc1ba4 x0 : ffffff8008dc1b58
Call trace:
__mmdrop+0x120/0x138
finish_cpu+0x68/0x70
cpuhp_invoke_callback+0xa8/0x800
_cpu_down+0x100/0x220
do_cpu_down+0x48/0x70
cpu_down+0x24/0x30
cpu_subsys_offline+0x20/0x30
device_offline+0xa4/0xd0
online_store+0x60/0xc0
dev_attr_store+0x44/0x60
sysfs_kf_write+0x5c/0x78
kernfs_fop_write+0xd8/0x1d0
__vfs_write+0x60/0x178
vfs_write+0xac/0x1b0
ksys_write+0x74/0xe8
__arm64_sys_write+0x24/0x30
el0_svc_common+0xa4/0x1a0
el0_svc_compat_handler+0x30/0x40
el0_svc_compat+0x8/0x18
Code: a94153f3 a9425bf5 a8c37bfd d65f03c0 (d4210000)
---[ end trace 0000000000000002 ]---
BUG: Bad rss-counter state mm:000000001136ddcb idx:0 val:1012
BUG: Bad rss-counter state mm:000000001136ddcb idx:1 val:5902
BUG: non-zero pgtables_bytes on freeing mm: 180224
Signed-off-by: Daniel Dragomir <daniel.drago...@windriver.com>
---
kernel/sched/core.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 218b93a..c62dbf9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5702,11 +5702,8 @@ void idle_task_exit(void)
switch_mm(mm, &init_mm, current);
finish_arch_post_lock_switch();
}
- /*
- * Defer the cleanup to an alive cpu. On RT we can neither
- * call mmdrop() nor mmdrop_delayed() from here.
- */
- per_cpu(idle_last_mm, smp_processor_id()) = mm;
+
+ /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
}
/*
--
2.7.4
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