Re: [syzbot] [trace?] WARNING in trace_rb_cpu_prepare

On Wed, 05 Aug 2026 23:39:30 -0700
syzbot [off-list ref] wrote:

------------[ cut here ]------------
failed to allocate ring buffer on CPU 1
WARNING: kernel/trace/ring_buffer.c:7976 at trace_rb_cpu_prepare+0x458/0x500 kernel/trace/ring_buffer.c:7976, CPU#1: syz.1.24/6005
Modules linked in:
CPU: 1 UID: 0 PID: 6005 Comm: syz.1.24 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:trace_rb_cpu_prepare+0x45a/0x500 kernel/trace/ring_buffer.c:7976
Code: 48 c1 ea 03 80 3c 02 00 0f 84 c7 fc ff ff 48 8b 3c 24 e8 29 0e 6c 00 e9 b9 fc ff ff e8 ff 83 fb ff 48 8d 3d b8 cc 17 0f 89 ee <67> 48 0f b9 3a bb f4 ff ff ff e9 df fd ff ff 4c 89 ef e8 ff 0d 6c
RSP: 0018:ffffc900036bf8c0 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88807a7604b8 RCX: ffff88807bafcf88
RDX: ffff88807b2dca80 RSI: 0000000000000001 RDI: ffffffff9126ada0
RBP: 0000000000000001 R08: ffff88807bafcf88 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff81000130 R12: 0000000000000001
R13: ffff88807a760410 R14: 0000000000000008 R15: 0000000000000162
FS:  00007f7d853056c0(0000) GS:ffff888123ed8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f118d5e5ff8 CR3: 000000006ff97000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 cpuhp_invoke_callback+0x205/0x9a0 kernel/cpu.c:204
 cpuhp_issue_call+0x1b8/0x970 kernel/cpu.c:2354
 __cpuhp_state_add_instance_cpuslocked+0x2d7/0x400 kernel/cpu.c:2423
 __cpuhp_state_add_instance+0xd7/0x2d0 kernel/cpu.c:2444
 cpuhp_state_add_instance include/linux/cpuhotplug.h:384 [inline]
 alloc_buffer+0x76c/0x1800 kernel/trace/ring_buffer.c:2830
 __ring_buffer_alloc+0x2d/0x40 kernel/trace/ring_buffer.c:2872
 allocate_trace_buffer+0x150/0xa30 kernel/trace/trace.c:8412
 allocate_trace_buffers kernel/trace/trace.c:8445 [inline]
 trace_array_create_systems+0x582/0xc30 kernel/trace/trace.c:8623
 trace_array_create kernel/trace/trace.c:8666 [inline]
 instance_mkdir+0xca/0x140 kernel/trace/trace.c:8681
 tracefs_syscall_mkdir+0x10e/0x180 fs/tracefs/inode.c:121

So you ran out of memory creating too many instances or something?

Yeah, that will trigger a warning.

-- Steve

 vfs_mkdir+0x361/0x850 fs/namei.c:5276
 filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309
 __do_sys_mkdirat fs/namei.c:5330 [inline]
 __se_sys_mkdirat fs/namei.c:5327 [inline]
 __x64_sys_mkdirat+0x89/0xc0 fs/namei.c:5327
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f