6.15-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt rostedt@goodmis.org
commit 327e28664307d49ce3fa71ba30dcc0007c270974 upstream.
When setting the funcgraph-args option when function graph tracer is net enabled, it incorrectly enables it. Worse, it unregisters itself when it was never registered. Then when it gets enabled again, it will register itself a second time causing a WARNing.
~# echo 1 > /sys/kernel/tracing/options/funcgraph-args ~# head -20 /sys/kernel/tracing/trace # tracer: nop # # entries-in-buffer/entries-written: 813/26317372 #P:8 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <idle>-0 [007] d..4. 358.966010: 7) 1.692 us | fetch_next_timer_interrupt(basej=4294981640, basem=357956000000, base_local=0xffff88823c3ae040, base_global=0xffff88823c3af300, tevt=0xffff888100e47cb8); <idle>-0 [007] d..4. 358.966012: 7) | tmigr_cpu_deactivate(nextexp=357988000000) { <idle>-0 [007] d..4. 358.966013: 7) | _raw_spin_lock(lock=0xffff88823c3b2320) { <idle>-0 [007] d..4. 358.966014: 7) 0.981 us | preempt_count_add(val=1); <idle>-0 [007] d..5. 358.966017: 7) 1.058 us | do_raw_spin_lock(lock=0xffff88823c3b2320); <idle>-0 [007] d..4. 358.966019: 7) 5.824 us | } <idle>-0 [007] d..5. 358.966021: 7) | tmigr_inactive_up(group=0xffff888100cb9000, child=0x0, data=0xffff888100e47bc0) { <idle>-0 [007] d..5. 358.966022: 7) | tmigr_update_events(group=0xffff888100cb9000, child=0x0, data=0xffff888100e47bc0) {
Notice the "tracer: nop" at the top there. The current tracer is the "nop" tracer, but the content is obviously the function graph tracer.
Enabling function graph tracing will cause it to register again and trigger a warning in the accounting:
~# echo function_graph > /sys/kernel/tracing/current_tracer -bash: echo: write error: Device or resource busy
With the dmesg of:
------------[ cut here ]------------ WARNING: CPU: 7 PID: 1095 at kernel/trace/ftrace.c:3509 ftrace_startup_subops+0xc1e/0x1000 Modules linked in: kvm_intel kvm irqbypass CPU: 7 UID: 0 PID: 1095 Comm: bash Not tainted 6.16.0-rc2-test-00006-gea03de4105d3 #24 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:ftrace_startup_subops+0xc1e/0x1000 Code: 48 b8 22 01 00 00 00 00 ad de 49 89 84 24 88 01 00 00 8b 44 24 08 89 04 24 e9 c3 f7 ff ff c7 04 24 ed ff ff ff e9 b7 f7 ff ff <0f> 0b c7 04 24 f0 ff ff ff e9 a9 f7 ff ff c7 04 24 f4 ff ff ff e9 RSP: 0018:ffff888133cff948 EFLAGS: 00010202 RAX: 0000000000000001 RBX: 1ffff1102679ff31 RCX: 0000000000000000 RDX: 1ffffffff0b27a60 RSI: ffffffff8593d2f0 RDI: ffffffff85941140 RBP: 00000000000c2041 R08: ffffffffffffffff R09: ffffed1020240221 R10: ffff88810120110f R11: ffffed1020240214 R12: ffffffff8593d2f0 R13: ffffffff8593d300 R14: ffffffff85941140 R15: ffffffff85631100 FS: 00007f7ec6f28740(0000) GS:ffff8882b5251000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f7ec6f181c0 CR3: 000000012f1d0005 CR4: 0000000000172ef0 Call Trace: <TASK> ? __pfx_ftrace_startup_subops+0x10/0x10 ? find_held_lock+0x2b/0x80 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 ? trace_preempt_on+0xd0/0x110 ? __pfx_trace_graph_entry_args+0x10/0x10 register_ftrace_graph+0x4d2/0x1020 ? tracing_reset_online_cpus+0x14b/0x1e0 ? __pfx_register_ftrace_graph+0x10/0x10 ? ring_buffer_record_enable+0x16/0x20 ? tracing_reset_online_cpus+0x153/0x1e0 ? __pfx_tracing_reset_online_cpus+0x10/0x10 ? __pfx_trace_graph_return+0x10/0x10 graph_trace_init+0xfd/0x160 tracing_set_tracer+0x500/0xa80 ? __pfx_tracing_set_tracer+0x10/0x10 ? lock_release+0x181/0x2d0 ? _copy_from_user+0x26/0xa0 tracing_set_trace_write+0x132/0x1e0 ? __pfx_tracing_set_trace_write+0x10/0x10 ? ftrace_graph_func+0xcc/0x140 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 ? ftrace_stub_direct_tramp+0x10/0x10 vfs_write+0x1d0/0xe90 ? __pfx_vfs_write+0x10/0x10
Have the setting of the funcgraph-args check if function_graph tracer is the current tracer of the instance, and if not, do nothing, as there's nothing to do (the option is checked when function_graph tracing starts).
Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Mark Rutland mark.rutland@arm.com Link: https://lore.kernel.org/20250618073801.057ea636@gandalf.local.home Fixes: c7a60a733c373 ("ftrace: Have funcgraph-args take affect during tracing") Closes: https://lore.kernel.org/all/4ab1a7bdd0174ab09c7b0d68cdbff9a4@huawei.com/ Reported-by: Changbin Du changbin.du@huawei.com Tested-by: Changbin Du changbin.du@huawei.com Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace_functions_graph.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/kernel/trace/trace_functions_graph.c +++ b/kernel/trace/trace_functions_graph.c @@ -475,10 +475,16 @@ static int graph_trace_init(struct trace return 0; }
+static struct tracer graph_trace; + static int ftrace_graph_trace_args(struct trace_array *tr, int set) { trace_func_graph_ent_t entry;
+ /* Do nothing if the current tracer is not this tracer */ + if (tr->current_trace != &graph_trace) + return 0; + if (set) entry = trace_graph_entry_args; else