Hello,
kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
in testcase: locktorture
version:
with following parameters:
runtime: 300s
test: cpuhotplug
compiler: clang-16
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
(please refer to attached dmesg/kmsg for entire log/backtrace)
+-----------------------------------------------------------------------+------------+------------+
| | 11b2bc2909 | 1254a620b4 |
+-----------------------------------------------------------------------+------------+------------+
| WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register | 0 | 12 |
| RIP:rcu_stall_chain_notifier_register | 0 | 12 |
+-----------------------------------------------------------------------+------------+------------+
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-lkp/[email protected]
[ 200.668175][ T876] ------------[ cut here ]------------
[ 200.669199][ T876] Adding torture_spin_lock_dump+0x0/0x20 [locktorture]() to RCU stall notifier list (failed, so all is well).
[ 200.671183][ T876] WARNING: CPU: 1 PID: 876 at kernel/rcu/tree_stall.h:1088 rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.673094][ T876] Modules linked in: locktorture(+) torture
[ 200.674129][ T876] CPU: 1 PID: 876 Comm: modprobe Tainted: G W N 6.6.0-03747-g1254a620b4a3 #1 44194d056aabc0fb2e11ad706d62f862fdc5dd23
[ 200.676413][ T876] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[ 200.678192][ T876] RIP: 0010:rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.679403][ T876] Code: 89 df e8 2f 0c 35 00 48 8b 33 85 ed 48 c7 c0 00 cb 49 97 48 c7 c2 a0 ca 49 97 48 0f 44 d0 48 c7 c7 40 ca 49 97 e8 fc 69 e4 ff <0f> 0b 85 ed 74 13 48 c7 c7 20 c7 1d 99 48 89 de 5b 41 5e 5d e9 83
All code
========
0: 89 df mov %ebx,%edi
2: e8 2f 0c 35 00 call 0x350c36
7: 48 8b 33 mov (%rbx),%rsi
a: 85 ed test %ebp,%ebp
c: 48 c7 c0 00 cb 49 97 mov $0xffffffff9749cb00,%rax
13: 48 c7 c2 a0 ca 49 97 mov $0xffffffff9749caa0,%rdx
1a: 48 0f 44 d0 cmove %rax,%rdx
1e: 48 c7 c7 40 ca 49 97 mov $0xffffffff9749ca40,%rdi
25: e8 fc 69 e4 ff call 0xffffffffffe46a26
2a:* 0f 0b ud2 <-- trapping instruction
2c: 85 ed test %ebp,%ebp
2e: 74 13 je 0x43
30: 48 c7 c7 20 c7 1d 99 mov $0xffffffff991dc720,%rdi
37: 48 89 de mov %rbx,%rsi
3a: 5b pop %rbx
3b: 41 5e pop %r14
3d: 5d pop %rbp
3e: e9 .byte 0xe9
3f: 83 .byte 0x83
Code starting with the faulting instruction
===========================================
0: 0f 0b ud2
2: 85 ed test %ebp,%ebp
4: 74 13 je 0x19
6: 48 c7 c7 20 c7 1d 99 mov $0xffffffff991dc720,%rdi
d: 48 89 de mov %rbx,%rsi
10: 5b pop %rbx
11: 41 5e pop %r14
13: 5d pop %rbp
14: e9 .byte 0xe9
15: 83 .byte 0x83
[ 200.682780][ T876] RSP: 0018:ffffc90002b67978 EFLAGS: 00010246
[ 200.683857][ T876] RAX: 000000000000006b RBX: ffffffffc040a220 RCX: 0000000000000027
[ 200.685304][ T876] RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffff8883aeb27a10
[ 200.686724][ T876] RBP: 0000000000000000 R08: ffff8883aeb27a13 R09: 1ffff11075d64f42
[ 200.688142][ T876] R10: dffffc0000000000 R11: ffffed1075d64f43 R12: ffff88814879e080
[ 200.689573][ T876] R13: ffffc90002b679e0 R14: dffffc0000000000 R15: dffffc0000000000
[ 200.690976][ T876] FS: 0000000000000000(0000) GS:ffff8883aeb00000(0063) knlGS:00000000f7aa9700
[ 200.692536][ T876] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
[ 200.693695][ T876] CR2: 000000005664b010 CR3: 0000000141a71000 CR4: 00000000000406f0
[ 200.695095][ T876] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 200.696540][ T876] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 200.698173][ T876] Call Trace:
[ 200.698865][ T876] <TASK>
[ 200.699476][ T876] ? __warn (kernel/panic.c:235 kernel/panic.c:673)
[ 200.700283][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.701381][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.702461][ T876] ? report_bug (lib/bug.c:?)
[ 200.703294][ T876] ? handle_bug (arch/x86/kernel/traps.c:237)
[ 200.704128][ T876] ? exc_invalid_op (arch/x86/kernel/traps.c:258)
[ 200.704995][ T876] ? asm_exc_invalid_op (arch/x86/include/asm/idtentry.h:568)
[ 200.705913][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.707177][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
[ 200.708908][ T876] init_module (include/linux/cpumask.h:909 kernel/locking/locktorture.c:98 kernel/locking/locktorture.c:1051) locktorture
[ 200.710509][ T876] do_one_initcall (init/main.c:1232)
[ 200.711382][ T876] ? 0xffffffffc0418000
[ 200.712246][ T876] ? __asan_register_globals (mm/kasan/generic.c:229)
[ 200.713299][ T876] do_init_module (kernel/module/main.c:2530)
[ 200.714163][ T876] __se_sys_finit_module (kernel/module/main.c:3148 kernel/module/main.c:3166 kernel/module/main.c:3186 kernel/module/main.c:3169)
[ 200.715119][ T876] __do_fast_syscall_32 (arch/x86/entry/common.c:164)
[ 200.716056][ T876] do_fast_syscall_32 (arch/x86/entry/common.c:255)
[ 200.716965][ T876] entry_SYSENTER_compat_after_hwframe (arch/x86/entry/entry_64_compat.S:121)
[ 200.718040][ T876] RIP: 0023:0xf7fbb539
[ 200.718801][ T876] Code: 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 cc 90 90 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
All code
========
0: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
4: 10 07 adc %al,(%rdi)
6: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
a: 10 08 adc %cl,(%rax)
c: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
...
20: 00 51 52 add %dl,0x52(%rcx)
23: 55 push %rbp
24:* 89 e5 mov %esp,%ebp <-- trapping instruction
26: 0f 34 sysenter
28: cd 80 int $0x80
2a: 5d pop %rbp
2b: 5a pop %rdx
2c: 59 pop %rcx
2d: c3 ret
2e: cc int3
2f: 90 nop
30: 90 nop
31: 90 nop
32: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
39: 00 00 00
3c: 0f .byte 0xf
3d: 1f (bad)
3e: 44 rex.R
...
Code starting with the faulting instruction
===========================================
0: 5d pop %rbp
1: 5a pop %rdx
2: 59 pop %rcx
3: c3 ret
4: cc int3
5: 90 nop
6: 90 nop
7: 90 nop
8: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
f: 00 00 00
12: 0f .byte 0xf
13: 1f (bad)
14: 44 rex.R
The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20231207/[email protected]
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Thu, Dec 07, 2023 at 04:19:56PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
>
> commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
> https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
Thank you for your testing efforts!
This one is expected behavior by explicit request from Linus Torvalds.
The concern is that people might use this hook without understanding
the risks of losing RCU CPU stall warnings.
One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
kernel boot parameter. Another would be to forgive this warning when
that boot parameter was specified. Your choice! ;-)
Thanx, Paul
> in testcase: locktorture
> version:
> with following parameters:
>
> runtime: 300s
> test: cpuhotplug
>
>
>
> compiler: clang-16
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>
> (please refer to attached dmesg/kmsg for entire log/backtrace)
>
>
> +-----------------------------------------------------------------------+------------+------------+
> | | 11b2bc2909 | 1254a620b4 |
> +-----------------------------------------------------------------------+------------+------------+
> | WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register | 0 | 12 |
> | RIP:rcu_stall_chain_notifier_register | 0 | 12 |
> +-----------------------------------------------------------------------+------------+------------+
>
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <[email protected]>
> | Closes: https://lore.kernel.org/oe-lkp/[email protected]
>
>
> [ 200.668175][ T876] ------------[ cut here ]------------
> [ 200.669199][ T876] Adding torture_spin_lock_dump+0x0/0x20 [locktorture]() to RCU stall notifier list (failed, so all is well).
> [ 200.671183][ T876] WARNING: CPU: 1 PID: 876 at kernel/rcu/tree_stall.h:1088 rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.673094][ T876] Modules linked in: locktorture(+) torture
> [ 200.674129][ T876] CPU: 1 PID: 876 Comm: modprobe Tainted: G W N 6.6.0-03747-g1254a620b4a3 #1 44194d056aabc0fb2e11ad706d62f862fdc5dd23
> [ 200.676413][ T876] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> [ 200.678192][ T876] RIP: 0010:rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.679403][ T876] Code: 89 df e8 2f 0c 35 00 48 8b 33 85 ed 48 c7 c0 00 cb 49 97 48 c7 c2 a0 ca 49 97 48 0f 44 d0 48 c7 c7 40 ca 49 97 e8 fc 69 e4 ff <0f> 0b 85 ed 74 13 48 c7 c7 20 c7 1d 99 48 89 de 5b 41 5e 5d e9 83
> All code
> ========
> 0: 89 df mov %ebx,%edi
> 2: e8 2f 0c 35 00 call 0x350c36
> 7: 48 8b 33 mov (%rbx),%rsi
> a: 85 ed test %ebp,%ebp
> c: 48 c7 c0 00 cb 49 97 mov $0xffffffff9749cb00,%rax
> 13: 48 c7 c2 a0 ca 49 97 mov $0xffffffff9749caa0,%rdx
> 1a: 48 0f 44 d0 cmove %rax,%rdx
> 1e: 48 c7 c7 40 ca 49 97 mov $0xffffffff9749ca40,%rdi
> 25: e8 fc 69 e4 ff call 0xffffffffffe46a26
> 2a:* 0f 0b ud2 <-- trapping instruction
> 2c: 85 ed test %ebp,%ebp
> 2e: 74 13 je 0x43
> 30: 48 c7 c7 20 c7 1d 99 mov $0xffffffff991dc720,%rdi
> 37: 48 89 de mov %rbx,%rsi
> 3a: 5b pop %rbx
> 3b: 41 5e pop %r14
> 3d: 5d pop %rbp
> 3e: e9 .byte 0xe9
> 3f: 83 .byte 0x83
>
> Code starting with the faulting instruction
> ===========================================
> 0: 0f 0b ud2
> 2: 85 ed test %ebp,%ebp
> 4: 74 13 je 0x19
> 6: 48 c7 c7 20 c7 1d 99 mov $0xffffffff991dc720,%rdi
> d: 48 89 de mov %rbx,%rsi
> 10: 5b pop %rbx
> 11: 41 5e pop %r14
> 13: 5d pop %rbp
> 14: e9 .byte 0xe9
> 15: 83 .byte 0x83
> [ 200.682780][ T876] RSP: 0018:ffffc90002b67978 EFLAGS: 00010246
> [ 200.683857][ T876] RAX: 000000000000006b RBX: ffffffffc040a220 RCX: 0000000000000027
> [ 200.685304][ T876] RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffff8883aeb27a10
> [ 200.686724][ T876] RBP: 0000000000000000 R08: ffff8883aeb27a13 R09: 1ffff11075d64f42
> [ 200.688142][ T876] R10: dffffc0000000000 R11: ffffed1075d64f43 R12: ffff88814879e080
> [ 200.689573][ T876] R13: ffffc90002b679e0 R14: dffffc0000000000 R15: dffffc0000000000
> [ 200.690976][ T876] FS: 0000000000000000(0000) GS:ffff8883aeb00000(0063) knlGS:00000000f7aa9700
> [ 200.692536][ T876] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
> [ 200.693695][ T876] CR2: 000000005664b010 CR3: 0000000141a71000 CR4: 00000000000406f0
> [ 200.695095][ T876] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 200.696540][ T876] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 200.698173][ T876] Call Trace:
> [ 200.698865][ T876] <TASK>
> [ 200.699476][ T876] ? __warn (kernel/panic.c:235 kernel/panic.c:673)
> [ 200.700283][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.701381][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.702461][ T876] ? report_bug (lib/bug.c:?)
> [ 200.703294][ T876] ? handle_bug (arch/x86/kernel/traps.c:237)
> [ 200.704128][ T876] ? exc_invalid_op (arch/x86/kernel/traps.c:258)
> [ 200.704995][ T876] ? asm_exc_invalid_op (arch/x86/include/asm/idtentry.h:568)
> [ 200.705913][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.707177][ T876] ? rcu_stall_chain_notifier_register (kernel/rcu/tree_stall.h:1087)
> [ 200.708908][ T876] init_module (include/linux/cpumask.h:909 kernel/locking/locktorture.c:98 kernel/locking/locktorture.c:1051) locktorture
> [ 200.710509][ T876] do_one_initcall (init/main.c:1232)
> [ 200.711382][ T876] ? 0xffffffffc0418000
> [ 200.712246][ T876] ? __asan_register_globals (mm/kasan/generic.c:229)
> [ 200.713299][ T876] do_init_module (kernel/module/main.c:2530)
> [ 200.714163][ T876] __se_sys_finit_module (kernel/module/main.c:3148 kernel/module/main.c:3166 kernel/module/main.c:3186 kernel/module/main.c:3169)
> [ 200.715119][ T876] __do_fast_syscall_32 (arch/x86/entry/common.c:164)
> [ 200.716056][ T876] do_fast_syscall_32 (arch/x86/entry/common.c:255)
> [ 200.716965][ T876] entry_SYSENTER_compat_after_hwframe (arch/x86/entry/entry_64_compat.S:121)
> [ 200.718040][ T876] RIP: 0023:0xf7fbb539
> [ 200.718801][ T876] Code: 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 cc 90 90 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
> All code
> ========
> 0: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
> 4: 10 07 adc %al,(%rdi)
> 6: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
> a: 10 08 adc %cl,(%rax)
> c: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
> ...
> 20: 00 51 52 add %dl,0x52(%rcx)
> 23: 55 push %rbp
> 24:* 89 e5 mov %esp,%ebp <-- trapping instruction
> 26: 0f 34 sysenter
> 28: cd 80 int $0x80
> 2a: 5d pop %rbp
> 2b: 5a pop %rdx
> 2c: 59 pop %rcx
> 2d: c3 ret
> 2e: cc int3
> 2f: 90 nop
> 30: 90 nop
> 31: 90 nop
> 32: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
> 39: 00 00 00
> 3c: 0f .byte 0xf
> 3d: 1f (bad)
> 3e: 44 rex.R
> ...
>
> Code starting with the faulting instruction
> ===========================================
> 0: 5d pop %rbp
> 1: 5a pop %rdx
> 2: 59 pop %rcx
> 3: c3 ret
> 4: cc int3
> 5: 90 nop
> 6: 90 nop
> 7: 90 nop
> 8: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
> f: 00 00 00
> 12: 0f .byte 0xf
> 13: 1f (bad)
> 14: 44 rex.R
>
>
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20231207/[email protected]
>
>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>
hi, Paul,
On Mon, Dec 11, 2023 at 08:59:16AM -0800, Paul E. McKenney wrote:
> On Thu, Dec 07, 2023 at 04:19:56PM +0800, kernel test robot wrote:
> >
> >
> > Hello,
> >
> > kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
> >
> > commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
> > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
>
> Thank you for your testing efforts!
>
> This one is expected behavior by explicit request from Linus Torvalds.
> The concern is that people might use this hook without understanding
> the risks of losing RCU CPU stall warnings.
>
> One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> kernel boot parameter. Another would be to forgive this warning when
> that boot parameter was specified. Your choice! ;-)
>
> Thanx, Paul
Thanks a lot for information!
this commit (1254a620b4) is a test for this warning, am I right?
when this warning mechanism goes into upstream, do you want us still report
for similar cases? or we could just ignore them? Thanks!
On Tue, Dec 12, 2023 at 10:06:36AM +0800, Oliver Sang wrote:
> hi, Paul,
>
> On Mon, Dec 11, 2023 at 08:59:16AM -0800, Paul E. McKenney wrote:
> > On Thu, Dec 07, 2023 at 04:19:56PM +0800, kernel test robot wrote:
> > >
> > >
> > > Hello,
> > >
> > > kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
> > >
> > > commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
> > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
> >
> > Thank you for your testing efforts!
> >
> > This one is expected behavior by explicit request from Linus Torvalds.
> > The concern is that people might use this hook without understanding
> > the risks of losing RCU CPU stall warnings.
> >
> > One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> > kernel boot parameter. Another would be to forgive this warning when
> > that boot parameter was specified. Your choice! ;-)
>
> Thanks a lot for information!
>
> this commit (1254a620b4) is a test for this warning, am I right?
> when this warning mechanism goes into upstream, do you want us still report
> for similar cases? or we could just ignore them? Thanks!
This 1254a620b4 ("EXP locktorture: Add RCU CPU stall-warning notifier
stub") commit is a debug-only use of this facility that will never go
upstream, as signified by the "EXP" at the beginning of the subject line.
Or is there some better way than "EXP" to mark commits that are not
intended for mainline?
Thanx, Paul
hi, Paul,
On Mon, Dec 11, 2023 at 08:26:12PM -0800, Paul E. McKenney wrote:
> On Tue, Dec 12, 2023 at 10:06:36AM +0800, Oliver Sang wrote:
> > hi, Paul,
> >
> > On Mon, Dec 11, 2023 at 08:59:16AM -0800, Paul E. McKenney wrote:
> > > On Thu, Dec 07, 2023 at 04:19:56PM +0800, kernel test robot wrote:
> > > >
> > > >
> > > > Hello,
> > > >
> > > > kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
> > > >
> > > > commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
> > > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
> > >
> > > Thank you for your testing efforts!
> > >
> > > This one is expected behavior by explicit request from Linus Torvalds.
> > > The concern is that people might use this hook without understanding
> > > the risks of losing RCU CPU stall warnings.
> > >
> > > One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> > > kernel boot parameter. Another would be to forgive this warning when
> > > that boot parameter was specified. Your choice! ;-)
> >
> > Thanks a lot for information!
> >
> > this commit (1254a620b4) is a test for this warning, am I right?
> > when this warning mechanism goes into upstream, do you want us still report
> > for similar cases? or we could just ignore them? Thanks!
>
> This 1254a620b4 ("EXP locktorture: Add RCU CPU stall-warning notifier
> stub") commit is a debug-only use of this facility that will never go
> upstream, as signified by the "EXP" at the beginning of the subject line.
>
> Or is there some better way than "EXP" to mark commits that are not
> intended for mainline?
>
> Thanx, Paul
>
sorry, seems I didn't state it very well. let me clarify.
the 'EXP' and "This not-for-mainline commit" is very good for us to know it
will not go into mainline.
what I asked is if this warning is triggered by other usages (not this
debug-only test), could we still ignore them by following below guidance you
gave us?
> > > One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> > > kernel boot parameter. Another would be to forgive this warning when
> > > that boot parameter was specified. Your choice! ;-)
On Tue, Dec 12, 2023 at 03:43:44PM +0800, Oliver Sang wrote:
> hi, Paul,
>
> On Mon, Dec 11, 2023 at 08:26:12PM -0800, Paul E. McKenney wrote:
> > On Tue, Dec 12, 2023 at 10:06:36AM +0800, Oliver Sang wrote:
> > > hi, Paul,
> > >
> > > On Mon, Dec 11, 2023 at 08:59:16AM -0800, Paul E. McKenney wrote:
> > > > On Thu, Dec 07, 2023 at 04:19:56PM +0800, kernel test robot wrote:
> > > > >
> > > > >
> > > > > Hello,
> > > > >
> > > > > kernel test robot noticed "WARNING:at_kernel/rcu/tree_stall.h:#rcu_stall_chain_notifier_register" on:
> > > > >
> > > > > commit: 1254a620b4a3832e65ac01bcef769b99e34515b2 ("EXP locktorture: Add RCU CPU stall-warning notifier stub")
> > > > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2023.11.08a
> > > >
> > > > Thank you for your testing efforts!
> > > >
> > > > This one is expected behavior by explicit request from Linus Torvalds.
> > > > The concern is that people might use this hook without understanding
> > > > the risks of losing RCU CPU stall warnings.
> > > >
> > > > One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> > > > kernel boot parameter. Another would be to forgive this warning when
> > > > that boot parameter was specified. Your choice! ;-)
> > >
> > > Thanks a lot for information!
> > >
> > > this commit (1254a620b4) is a test for this warning, am I right?
> > > when this warning mechanism goes into upstream, do you want us still report
> > > for similar cases? or we could just ignore them? Thanks!
> >
> > This 1254a620b4 ("EXP locktorture: Add RCU CPU stall-warning notifier
> > stub") commit is a debug-only use of this facility that will never go
> > upstream, as signified by the "EXP" at the beginning of the subject line.
> >
> > Or is there some better way than "EXP" to mark commits that are not
> > intended for mainline?
> >
> > Thanx, Paul
> >
>
> sorry, seems I didn't state it very well. let me clarify.
>
> the 'EXP' and "This not-for-mainline commit" is very good for us to know it
> will not go into mainline.
>
> what I asked is if this warning is triggered by other usages (not this
> debug-only test), could we still ignore them by following below guidance you
> gave us?
Ah, got it! I could imagine someone pushing out a not-for-mainline use
of this facility in order to allow others to run their test. Actually,
I could also imagine me doing that. ;-)
Thanx, Paul
> > > > One fix would be to never specify the rcupdate.rcu_cpu_stall_notifiers
> > > > kernel boot parameter. Another would be to forgive this warning when
> > > > that boot parameter was specified. Your choice! ;-)