From: "Naveen N. Rao" If instance directories are deleted while there are registered function triggers: # cd /sys/kernel/debug/tracing/instances # mkdir test # echo "schedule:enable_event:sched:sched_switch" > test/set_ftrace_filter # rmdir test Unable to handle kernel paging request for data at address 0x00000008 Unable to handle kernel paging request for data at address 0x00000008 Faulting instruction address: 0xc0000000021edde8 Oops: Kernel access of bad area, sig: 11 [#1] SMP NR_CPUS=2048 NUMA pSeries Modules linked in: iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc kvm iptable_filter fuse binfmt_misc pseries_rng rng_core vmx_crypto ib_iser rdma_cm iw_cm ib_cm ib_core libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c multipath virtio_net virtio_blk virtio_pci crc32c_vpmsum virtio_ring virtio CPU: 8 PID: 8694 Comm: rmdir Not tainted 4.11.0-nnr+ #113 task: c0000000bab52800 task.stack: c0000000baba0000 NIP: c0000000021edde8 LR: c0000000021f0590 CTR: c000000002119620 REGS: c0000000baba3870 TRAP: 0300 Not tainted (4.11.0-nnr+) MSR: 8000000000009033 CR: 22002422 XER: 20000000 CFAR: 00007fffabb725a8 DAR: 0000000000000008 DSISR: 40000000 SOFTE: 0 GPR00: c00000000220f750 c0000000baba3af0 c000000003157e00 0000000000000000 GPR04: 0000000000000040 00000000000000eb 0000000000000040 0000000000000000 GPR08: 0000000000000000 0000000000000113 0000000000000000 c00000000305db98 GPR12: c000000002119620 c00000000fd42c00 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 GPR20: 0000000000000000 0000000000000000 c0000000bab52e90 0000000000000000 GPR24: 0000000000000000 00000000000000eb 0000000000000040 c0000000baba3bb0 GPR28: c00000009cb06eb0 c0000000bab52800 c00000009cb06eb0 c0000000baba3bb0 NIP [c0000000021edde8] ring_buffer_lock_reserve+0x8/0x4e0 LR [c0000000021f0590] trace_event_buffer_lock_reserve+0xe0/0x1a0 Call Trace: [c0000000baba3af0] [c0000000021f96c8] trace_event_buffer_commit+0x1b8/0x280 (unreliable) [c0000000baba3b60] [c00000000220f750] trace_event_buffer_reserve+0x80/0xd0 [c0000000baba3b90] [c0000000021196b8] trace_event_raw_event_sched_switch+0x98/0x180 [c0000000baba3c10] [c0000000029d9980] __schedule+0x6e0/0xab0 [c0000000baba3ce0] [c000000002122230] do_task_dead+0x70/0xc0 [c0000000baba3d10] [c0000000020ea9c8] do_exit+0x828/0xd00 [c0000000baba3dd0] [c0000000020eaf70] do_group_exit+0x60/0x100 [c0000000baba3e10] [c0000000020eb034] SyS_exit_group+0x24/0x30 [c0000000baba3e30] [c00000000200bcec] system_call+0x38/0x54 Instruction dump: 60000000 60420000 7d244b78 7f63db78 4bffaa09 393efff8 793e0020 39200000 4bfffecc 60420000 3c4c00f7 3842a020 <81230008> 2f890000 409e02f0 a14d0008 ---[ end trace b917b8985d0e650b ]--- Unable to handle kernel paging request for data at address 0x00000008 Faulting instruction address: 0xc0000000021edde8 Unable to handle kernel paging request for data at address 0x00000008 Faulting instruction address: 0xc0000000021edde8 Faulting instruction address: 0xc0000000021edde8 To address this, let's clear all registered function probes before deleting the ftrace instance. Link: http://lkml.kernel.org/r/c5f1ca624043690bd94642bb6bffd3f2fc504035.1494956770.git.naveen.n.rao@linux.vnet.ibm.com Reported-by: Michael Ellerman Signed-off-by: Naveen N. Rao Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 8 ++++++++ kernel/trace/trace.c | 3 +++ kernel/trace/trace.h | 1 + 3 files changed, 12 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index c35c3e67d09a..74fdfe9ed3db 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4256,6 +4256,14 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr, return ret; } +void clear_ftrace_function_probes(struct trace_array *tr) +{ + struct ftrace_func_probe *probe, *n; + + list_for_each_entry_safe(probe, n, &tr->func_probes, list) + unregister_ftrace_function_probe_func(NULL, tr, probe->probe_ops); +} + static LIST_HEAD(ftrace_commands); static DEFINE_MUTEX(ftrace_cmd_mutex); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index cdf97ce8cff2..664c44a6d48f 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7550,6 +7550,9 @@ static int instance_rmdir(const char *name) } tracing_set_nop(tr); +#if defined(CONFIG_FUNCTION_TRACER) && defined(CONFIG_DYNAMIC_FTRACE) + clear_ftrace_function_probes(tr); +#endif event_trace_del_tracer(tr); ftrace_clear_pids(tr); ftrace_destroy_function_files(tr); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 291a1bca5748..98e0845f7235 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -980,6 +980,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr, extern int unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr, struct ftrace_probe_ops *ops); +extern void clear_ftrace_function_probes(struct trace_array *tr); int register_ftrace_command(struct ftrace_func_command *cmd); int unregister_ftrace_command(struct ftrace_func_command *cmd); -- 2.10.2