While running LTP tracing the following kernel warning was noticed on qemu_arm running linux next 20201001 kernel. I have not bisected this problem yet.

Reported-by: Naresh Kamboju naresh.kamboju@linaro.org

steps to reproduce: # boot qemu arm with linux next 20201001 tag kernel and this command line

/usr/bin/qemu-system-aarch64 -cpu host,aarch64=off -machine virt-2.10,accel=kvm -nographic -net nic,model=virtio,macaddr=BA:DD:AD:CC:09:02 -net tap -m 2048 -monitor none -kernel /kernel/zImage --append "console=ttyAMA0 root=/dev/vda rw" -hda /rootfs/rpb-console-image-lkft-am57xx-evm-20200723162735-41.rootfs.ext4 -m 4096 -smp 2 -nographic

# cd /opt/ltp/ # ./runltp -s tracing

metadata: git branch: master git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next git commit: d39294091fee6b89d9c4a683bb19441b25098330 git describe: next-20201001 make_kernelversion: 5.9.0-rc7 kernel-config: https://builds.tuxbuild.com/hw-PTbFtm7XJ15ZoA5Agjw/kernel.config

Test output log: -------------------- ftrace_buffer_size_kb.sh: line 33: echo: write error: Cannot allocate memory ftrace_buffer_size_kb.sh: line 33: echo: write error: Cannot allocate memory [ 118.092279] 8<--- cut here --- [ 118.093743] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 118.097204] pgd = 5cbbb903 [ 118.098406] [00000000] *pgd=00000000 [ 118.099886] Internal error: Oops: 5 [#1] SMP ARM [ 118.102124] Modules linked in: crc32_arm_ce sha2_arm_ce sha256_arm sha1_arm_ce sha1_arm aes_arm_ce crypto_simd [ 118.107642] CPU: 0 PID: 919 Comm: (agetty) Not tainted 5.9.0-rc7-next-20201001 #1 [ 118.111384] Hardware name: Generic DT based system [ 118.113677] PC is at __traceiter_rcu_dyntick+0x34/0x68 [ 118.116173] LR is at rcu_nmi_enter+0x158/0x17c [ 118.118348] pc : [<c03cd414>] lr : [<c12517c0>] psr: 60000093 [ 118.121347] sp : eb333c20 ip : c03cd3f8 fp : eb333c4c [ 118.123862] r10: eb333e18 r9 : c18da374 r8 : 005f67aa [ 118.126722] r7 : 40000000 r6 : 40000002 r5 : ee4d5ec0 r4 : 00000000 [ 118.129822] r3 : 40000002 r2 : 40000000 r1 : c18da374 r0 : c1f30ca0 [ 118.132978] Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none [ 118.136502] Control: 10c5383d Table: 690a406a DAC: 00000051 [ 118.139302] Process (agetty) (pid: 919, stack limit = 0x423671c1) [ 118.142166] Stack: (0xeb333c20 to 0xeb334000) [ 118.144241] 3c20: eb333ccc eb333c30 00000002 ee4d5ec0 eb332000 00000000 c1d04f54 0000001f [ 118.148079] 3c40: eb333c7c eb333c50 c12517c0 c03cd3ec 005f67aa c1cbac10 60000093 c0500464 [ 118.151904] 3c60: ffffe000 c1f31380 c0502384 00000001 eb333c8c eb333c80 c12517f4 c1251674 [ 118.155748] 3c80: eb333ca4 eb333c90 c03db214 c12517f0 c1cbac10 c0500464 eb333ccc eb333ca8 [ 118.159746] 3ca0: c044bd08 c03db1f8 ebba56c0 00000dc0 c051d0cc 60000013 ee4d9258 c1f9b28c [ 118.163658] 3cc0: eb333cf4 eb333cd0 c0500464 c044bc00 ed9006c0 00000000 00000000 00000dc0 [ 118.167535] 3ce0: c1d056e0 c1f9b28c eb333d3c eb333cf8 c0502384 c0500408 ffffe000 687b39a1 [ 118.171412] 3d00: eb333d34 c1da6628 c051d0cc 0000f0f4 00020101 c1da6628 eb27d180 00020101 [ 118.175257] 3d20: 00020101 000002c0 00000000 eb333e18 eb333d5c eb333d40 c051d0cc c0501ebc [ 118.179074] 3d40: c1da6628 c1d04bc0 eb27d180 00020101 eb333d8c eb333d60 c051d570 c051d0a8 [ 118.182905] 3d60: 00000001 eb333e18 eb332000 eb332000 eb333ee8 eb333ee8 eb333e18 ffffff9c [ 118.187135] 3d80: eb333e14 eb333d90 c052d17c c051d514 c052e0e0 00000403 eb333dcc eb333da8 [ 118.191102] 3da0: c0452290 c043b58c 40000013 eb332000 00000041 eb332000 ed8e8000 00001000 [ 118.195036] 3dc0: eb333e14 eb333dd0 c04bc420 c0452218 ed805080 687b39a1 ed8e8000 eb332000 [ 118.198974] 3de0: 00000003 687b39a1 00000000 eb332000 eb332000 eb333ee8 00000001 eb333e18 [ 118.203347] 3e00: ffffff9c ffffff9c eb333ed4 eb333e18 c052f61c c052d13c ebe70800 e81167c0 [ 118.207566] 3e20: 00000000 00100000 eb333e94 eb333e38 c03131b4 c044d940 ebe70800 00000003 [ 118.211702] 3e40: 00000003 00000000 c05404f0 c0541488 ebe70800 00000000 eb333e5c 00100000 [ 118.215701] 3e60: eb333e94 687b39a1 c03131b4 00000003 ebe70800 e81167c0 00000000 00100000 [ 118.219782] 3e80: 000a0101 00000100 eb333ec4 edbb3000 00000000 c05404e4 ffffff9c eb332000 [ 118.223752] 3ea0: eb333f30 edbb3000 00000000 687b39a1 ffffff9c eb332000 00000003 edbb3000 [ 118.227999] 3ec0: 00000000 eb332000 eb333f2c eb333ed8 c0516c78 c052f5ac eb333f0c eb333ee8 [ 118.231954] 3ee0: c035fa10 eb27dd70 00020101 687b0000 00000002 00000100 00000001 687b39a1 [ 118.236161] 3f00: 00000142 00000000 00000000 000a0101 00000000 eb332000 ffffff9c 00605738 [ 118.240218] 3f20: eb333f94 eb333f30 c0518374 c0516a70 000a0101 00000000 00000000 00000000 [ 118.244210] 3f40: 00000000 00000000 000a0101 00000000 00000000 00000000 00000000 00000000 [ 118.248508] 3f60: 00000000 687b39a1 00000142 00000000 00000000 b6f25900 00000142 c0300284 [ 118.252549] 3f80: eb332000 00000142 eb333fa4 eb333f98 c05183fc c05182e8 00000000 eb333fa8 [ 118.256884] 3fa0: c03000c0 c05183ec 00000000 00000000 ffffff9c 00605738 000a0101 00000000 [ 118.261036] 3fc0: 00000000 00000000 b6f25900 00000142 00605738 00000000 00000001 befa7514 [ 118.265154] 3fe0: b6c15210 befa7440 b6db7380 b6bfe338 60000010 ffffff9c 00000000 00000000 [ 118.269399] Backtrace: [ 118.270680] [<c03cd3e0>] (__traceiter_rcu_dyntick) from [<c12517c0>] (rcu_nmi_enter+0x158/0x17c) [ 118.275211] r9:0000001f r8:c1d04f54 r7:00000000 r6:eb332000 r5:ee4d5ec0 r4:00000002 [ 118.278994] [<c1251668>] (rcu_nmi_enter) from [<c12517f4>] (rcu_irq_enter+0x10/0x14) [ 118.282731] r9:00000001 r8:c0502384 r7:c1f31380 r6:ffffe000 r5:c0500464 r4:60000093 [ 118.286527] [<c12517e4>] (rcu_irq_enter) from [<c03db214>] (rcu_irq_enter_irqson+0x28/0x44) [ 118.290545] [<c03db1ec>] (rcu_irq_enter_irqson) from [<c044bd08>] (trace_hardirqs_on+0x114/0x1b0) [ 118.294786] r5:c0500464 r4:c1cbac10 [ 118.296529] [<c044bbf4>] (trace_hardirqs_on) from [<c0500464>] (__slab_alloc.constprop.0+0x68/0x6c) [ 118.300895] r9:c1f9b28c r8:ee4d9258 r7:60000013 r6:c051d0cc r5:00000dc0 r4:ebba56c0 [ 118.304648] [<c05003fc>] (__slab_alloc.constprop.0) from [<c0502384>] (kmem_cache_alloc+0x4d4/0x684) [ 118.309048] r9:c1f9b28c r8:c1d056e0 r7:00000dc0 r6:00000000 r5:00000000 r4:ed9006c0 [ 118.312803] [<c0501eb0>] (kmem_cache_alloc) from [<c051d0cc>] (__alloc_file+0x30/0xd4) [ 118.316606] r10:eb333e18 r9:00000000 r8:000002c0 r7:00020101 r6:00020101 r5:eb27d180 [ 118.320369] r4:c1da6628 [ 118.321632] [<c051d09c>] (__alloc_file) from [<c051d570>] (alloc_empty_file+0x68/0x130) [ 118.325452] r7:00020101 r6:eb27d180 r5:c1d04bc0 r4:c1da6628 [ 118.328214] [<c051d508>] (alloc_empty_file) from [<c052d17c>] (path_openat+0x4c/0xe2c) [ 118.332028] r9:ffffff9c r8:eb333e18 r7:eb333ee8 r6:eb333ee8 r5:eb332000 r4:eb332000 [ 118.335759] [<c052d130>] (path_openat) from [<c052f61c>] (do_filp_open+0x7c/0xe8) [ 118.339432] r10:ffffff9c r9:ffffff9c r8:eb333e18 r7:00000001 r6:eb333ee8 r5:eb332000 [ 118.343198] r4:eb332000 [ 118.344449] [<c052f5a0>] (do_filp_open) from [<c0516c78>] (do_sys_openat2+0x214/0x2d4) [ 118.348303] r8:eb332000 r7:00000000 r6:edbb3000 r5:00000003 r4:eb332000 [ 118.351537] [<c0516a64>] (do_sys_openat2) from [<c0518374>] (do_sys_open+0x98/0xd4) [ 118.355219] r10:00605738 r9:ffffff9c r8:eb332000 r7:00000000 r6:000a0101 r5:00000000 [ 118.358972] r4:00000000 [ 118.360235] [<c05182dc>] (do_sys_open) from [<c05183fc>] (sys_openat+0x1c/0x20) [ 118.363722] r10:00000142 r9:eb332000 r8:c0300284 r7:00000142 r6:b6f25900 r5:00000000 [ 118.367455] r4:00000000 [ 118.368707] [<c05183e0>] (sys_openat) from [<c03000c0>] (ret_fast_syscall+0x0/0x28) [ 118.372366] Exception stack(0xeb333fa8 to 0xeb333ff0) [ 118.374829] 3fa0: 00000000 00000000 ffffff9c 00605738 000a0101 00000000 [ 118.378763] 3fc0: 00000000 00000000 b6f25900 00000142 00605738 00000000 00000001 befa7514 [ 118.382680] 3fe0: b6c15210 befa7440 b6db7380 b6bfe338 [ 118.385101] Code: e1a09001 e590415c e1a07002 e1a06003 (e5945000) [ 118.388047] ---[ end trace d9dd2a672e7123ad ]---

full test log https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20201001/tes...