Hi,
On a P2020 (e500v2, two CPUs) running 7.3-rc1 with
CONFIG_PROVE_LOCKING and CONFIG_STRICT_KERNEL_RWX, the BPF JIT
triggers this warning at boot:
WARNING: kernel/smp.c:917 at smp_call_function_many_cond+0x430/0x818, CPU#1:
swapper/0/1
CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.3.0-rc1-leds-v4 #1 PREEMPT
Hardware name: Turris 1.1 e500v2 0x80211051 Freescale P2020
Call Trace:
[c1915bc0] [c001be04] flush_tlb_kernel_range+0x2c/0x74
[c1915bd0] [c001ce2c] patch_instructions+0x1b0/0x318
[c1915c20] [c003113c] bpf_arch_text_copy+0x5c/0xb4
[c1915c40] [c01c3398] bpf_jit_binary_pack_finalize+0x28/0x8c
[c1915c60] [c0031770] bpf_int_jit_compile+0x5dc/0x758
...
[c1915dd0] [c102e114] ptp_classifier_init+0x30/0x4c
[c1915df0] [c102d3a8] sock_init+0xc8/0xe4
...
hardirqs last disabled at (3076): [<c001ceb4>] patch_instructions+0x238/0x318
patch_mem() and patch_instructions() disable interrupts and then call
flush_tlb_kernel_range(). On nohash SMP that is
smp_call_function(do_flush_tlb_mm_ipi, NULL, 1), which waits for the
other CPU with interrupts off. If the other CPU is doing the same, both
wait for each other.
I think this is why the CZ.NIC Turris 1.1 hangs early in boot with
CONFIG_JUMP_LABEL=y. On 6.18.44 it hung in 19 of 19 boots and booted
fine 9 of 9 times with jump labels off. The hang comes while static
keys are patched and modules are loaded, nothing is printed and the
watchdog resets the board. OpenWrt keeps jump labels off on these
boards for now.
The same problem in change_page_attr() was fixed in 2017 by commit
7c6a4f3b1641 ("powerpc/mm: Call flush_tlb_kernel_range with interrupts
enabled").
I can test patches on the board.
Josef
