syzbot

 sign-in | mailing list | source | docs
🐞 Open [826]
🐞 Fixed [84]
🐞 Invalid [1048]
⬇ Missing Backports [127]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

WARNING: suspicious RCU usage in get_callchain_entry

Status: upstream: reported C repro on 2024/06/13 11:30
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+fc37d916410f29b8588d@syzkaller.appspotmail.com
First crash: 491d, last: 1d01h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2024/06/28 upstream (ToT) 5bbd9b249880 C [report] WARNING: suspicious RCU usage in get_callchain_entry
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 WARNING: suspicious RCU usage in get_callchain_entry origin:upstream 4 C 304 2d17h 121d 0/2 upstream: reported C repro on 2025/06/18 02:15
linux-6.1 WARNING: suspicious RCU usage in get_callchain_entry origin:upstream missing-backport 4 C 1062 2d16h 539d 0/3 upstream: reported C repro on 2024/04/26 10:45
upstream WARNING: suspicious RCU usage in get_callchain_entry perf 4 C error 8597 1d08h 535d 0/29 upstream: reported C repro on 2024/04/30 10:49
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/07/15 11:02 14m radoslaw.zielonek@gmail.com patch linux-5.15.y OK log

Sample crash report:
=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
kernel/events/callchain.c:161 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.0.17/4321:
 #0: ffffffff8c11c5e0 (rcu_read_lock_trace){....}-{0:0}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4321 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 get_callchain_entry+0x2a5/0x3b0 kernel/events/callchain.c:161
 get_perf_callchain+0x9f/0x480 kernel/events/callchain.c:187
 __bpf_get_stack+0x2cb/0x4f0 kernel/bpf/stackmap.c:482
 ____bpf_get_stack_raw_tp kernel/trace/bpf_trace.c:1490 [inline]
 bpf_get_stack_raw_tp+0x189/0x1c0 kernel/trace/bpf_trace.c:1480
 bpf_prog_b8a90dd1efcc4ad9+0x3d/0x4dc
 bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
 __bpf_prog_run include/linux/filter.h:628 [inline]
 bpf_prog_run include/linux/filter.h:635 [inline]
 bpf_prog_run_pin_on_cpu+0x63/0x140 include/linux/filter.h:652
 bpf_prog_test_run_syscall+0x354/0x4e0 net/bpf/test_run.c:1061
 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3368
 __sys_bpf+0x535/0x670 kernel/bpf/syscall.c:4669
 __do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f357da06be9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe253530e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f357dc3dfa0 RCX: 00007f357da06be9
RDX: 000000000000000c RSI: 00002000000004c0 RDI: 000000000000000a
RBP: 00007f357da89e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f357dc3dfa0 R14: 00007f357dc3dfa0 R15: 0000000000000003
 </TASK>

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
include/linux/perf_event.h:1274 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.0.17/4321:
 #0: ffffffff8c11c5e0 (rcu_read_lock_trace){....}-{0:0}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4321 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 perf_get_guest_cbs include/linux/perf_event.h:1274 [inline]
 perf_callchain_user+0x6d3/0x10e0 arch/x86/events/core.c:2870
 get_perf_callchain+0x35d/0x480 kernel/events/callchain.c:221
 __bpf_get_stack+0x2cb/0x4f0 kernel/bpf/stackmap.c:482
 ____bpf_get_stack_raw_tp kernel/trace/bpf_trace.c:1490 [inline]
 bpf_get_stack_raw_tp+0x189/0x1c0 kernel/trace/bpf_trace.c:1480
 bpf_prog_b8a90dd1efcc4ad9+0x3d/0x4dc
 bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
 __bpf_prog_run include/linux/filter.h:628 [inline]
 bpf_prog_run include/linux/filter.h:635 [inline]
 bpf_prog_run_pin_on_cpu+0x63/0x140 include/linux/filter.h:652
 bpf_prog_test_run_syscall+0x354/0x4e0 net/bpf/test_run.c:1061
 bpf_prog_test_run+0x31e/0x390 kernel/bpf/syscall.c:3368
 __sys_bpf+0x535/0x670 kernel/bpf/syscall.c:4669
 __do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
 __x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f357da06be9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe253530e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f357dc3dfa0 RCX: 00007f357da06be9
RDX: 000000000000000c RSI: 00002000000004c0 RDI: 000000000000000a
RBP: 00007f357da89e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f357dc3dfa0 R14: 00007f357dc3dfa0 R15: 0000000000000003
 </TASK>

Crashes (959):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/07 17:27 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/04 09:53 linux-5.15.y 01879f56bdde d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/04 08:26 linux-5.15.y 01879f56bdde d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/07/30 02:52 linux-5.15.y c79648372d02 f8f2b4da .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/07/30 01:41 linux-5.15.y c79648372d02 f8f2b4da .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/07/30 01:12 linux-5.15.y c79648372d02 f8f2b4da .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/07/25 20:21 linux-5.15.y c79648372d02 fb8f743d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/05/14 12:12 linux-5.15.y 3b8db0e4f263 7344edeb .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/03/19 22:18 linux-5.15.y 0c935c049b5c e20d7b13 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/01/11 11:56 linux-5.15.y 4735586da88e 6dbc6a9b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/01/04 20:26 linux-5.15.y 91786f140358 f3558dbf .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/01/04 19:15 linux-5.15.y 91786f140358 f3558dbf .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/01/04 04:45 linux-5.15.y 91786f140358 f3558dbf .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/01/04 04:05 linux-5.15.y 91786f140358 f3558dbf .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2024/11/18 06:49 linux-5.15.y 0a51d2d4527b cfe3a04a .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2024/07/28 09:13 linux-5.15.y 7e89efd3ae1c 46eb10b7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2024/06/29 23:09 linux-5.15.y 4878aadf2d15 757f06b1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2024/06/28 23:35 linux-5.15.y 4878aadf2d15 757f06b1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2024/06/13 13:14 linux-5.15.y c61bd26ae81a 2aa5052f .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/16 15:07 linux-5.15.y 29e53a5b1c4f 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/15 02:02 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/15 01:01 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 23:04 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 21:21 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 14:27 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 13:16 linux-5.15.y 29e53a5b1c4f b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 10:36 linux-5.15.y 29e53a5b1c4f ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/13 06:52 linux-5.15.y 29e53a5b1c4f ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/09 18:34 linux-5.15.y 29e53a5b1c4f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/09 18:34 linux-5.15.y 29e53a5b1c4f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/09 10:54 linux-5.15.y 29e53a5b1c4f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/07 19:09 linux-5.15.y 29e53a5b1c4f 8ef35d49 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/05 22:50 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/05 13:27 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/05 10:49 linux-5.15.y 29e53a5b1c4f 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/02 10:11 linux-5.15.y 43bb85222e53 267f56c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/02 03:31 linux-5.15.y 43bb85222e53 267f56c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/10/01 20:51 linux-5.15.y 43bb85222e53 a1859138 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/10/01 14:52 linux-5.15.y 43bb85222e53 a1859138 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/26 03:38 linux-5.15.y 43bb85222e53 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/26 01:46 linux-5.15.y 43bb85222e53 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/20 05:13 linux-5.15.y 43bb85222e53 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/19 22:51 linux-5.15.y 43bb85222e53 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/17 09:58 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/16 18:47 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/16 00:48 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/15 02:01 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/14 02:35 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/14 02:35 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/13 07:21 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/13 05:58 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/13 03:43 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/12 19:26 linux-5.15.y 43bb85222e53 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/09 12:02 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/08 20:55 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/08 03:08 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/08 00:18 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/07 19:45 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/06 22:12 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/09/06 14:54 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/09/01 03:48 linux-5.15.y 01879f56bdde 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/08/31 07:17 linux-5.15.y 01879f56bdde 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/08/24 05:45 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf WARNING: suspicious RCU usage in get_callchain_entry
2025/08/24 02:03 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/08/24 01:59 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2025/08/23 21:54 linux-5.15.y c79648372d02 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
2024/06/13 11:29 linux-5.15.y c61bd26ae81a 2aa5052f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan WARNING: suspicious RCU usage in get_callchain_entry
* Struck through repros no longer work on HEAD.