For kernels built with CONFIG_NO_HZ_FULL=y, running the following tests:
runqemu kvm slirp nographic qemuparams="-m 1024 -smp 4" bootparams=
"console=ttyS0 nohz_full=0,1 rcu_nocbs=0,1 sched_verbose" -d
root@qemux86-64:~# echo 0 > /sys/devices/system/cpu/cpu2/online
root@qemux86-64:~# echo 0 > /sys/devices/system/cpu/cpu3/online
[ 22.838290] BUG: unable to handle page fault for address: ffffffff84cd48c0
[ 22.839409] #PF: supervisor read access in kernel mode
[ 22.840215] #PF: error_code(0x0000) - not-present page
[ 22.841028] PGD 3e19067 P4D 3e19067 PUD 3e1a063 PMD 800ffffffb3ff062
[ 22.841889] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN PTI
[ 22.842175] CPU: 0 PID: 16 Comm: rcu_preempt Not tainted 6.2.0-rc1-yocto-standard+ #658
[ 22.842534] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.o4
[ 22.843036] RIP: 0010:do_raw_spin_trylock+0x70/0x120
[ 22.843267] Code: 81 c7 00 f1 f1 f1 f1 c7 40 04 04 f3 f3 f3 65
48 8b 04 25 28 00 00 00 48 89 45 e0 31 c0 e8 b8 0
[ 22.844187] RSP: 0018:ffff8880072b7b30 EFLAGS: 00010046
[ 22.844429] RAX: 0000000000000000 RBX: ffffffff84cd48c0 RCX: dffffc0000000000
[ 22.844751] RDX: 0000000000000003 RSI: 0000000000000004 RDI: ffffffff84cd48c0
[ 22.845074] RBP: ffff8880072b7ba8 R08: ffffffff811daa20 R09: fffffbfff099a919
[ 22.845400] R10: ffffffff84cd48c3 R11: fffffbfff099a918 R12: 1ffff11000e56f66
[ 22.845719] R13: ffffffff84cd48d8 R14: ffffffff84cd48c0 R15: ffff8880072b7cd8
[ 22.846040] FS: 0000000000000000(0000) GS:ffff888035200000(0000) knlGS:0000000000000000
[ 22.846403] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 22.846667] CR2: ffffffff84cd48c0 CR3: 000000001036c000 CR4: 00000000001506f0
[ 22.846988] Call Trace:
[ 22.847105] <TASK>
[ 22.847208] ? __pfx_do_raw_spin_trylock+0x10/0x10
[ 22.847430] ? rcu_read_unlock+0x26/0x80
[ 22.847612] ? trace_preempt_off+0x2a/0x130
[ 22.847812] _raw_spin_lock+0x41/0x80
[ 22.847984] ? schedule_timeout+0x242/0x580
[ 22.848178] schedule_timeout+0x242/0x580
[ 22.848366] ? __pfx_schedule_timeout+0x10/0x10
[ 22.848575] ? __pfx_do_raw_spin_trylock+0x10/0x10
[ 22.848796] ? __pfx_process_timeout+0x10/0x10
[ 22.849005] ? _raw_spin_unlock_irqrestore+0x46/0x80
[ 22.849232] ? prepare_to_swait_event+0xb8/0x210
[ 22.849450] rcu_gp_fqs_loop+0x66e/0xe70
[ 22.849633] ? rcu_gp_init+0x87c/0x1130
[ 22.849813] ? __pfx_rcu_gp_fqs_loop+0x10/0x10
[ 22.850022] ? _raw_spin_unlock_irqrestore+0x46/0x80
[ 22.850251] ? finish_swait+0xce/0x100
[ 22.850429] rcu_gp_kthread+0x2ea/0x6b0
[ 22.850608] ? __pfx_do_raw_spin_trylock+0x10/0x10
[ 22.850829] ? __pfx_rcu_gp_kthread+0x10/0x10
[ 22.851039] ? __kasan_check_read+0x11/0x20
[ 22.851233] ? __kthread_parkme+0xe8/0x110
[ 22.851424] ? __pfx_rcu_gp_kthread+0x10/0x10
[ 22.851627] kthread+0x172/0x1a0
[ 22.851781] ? __pfx_kthread+0x10/0x10
[ 22.851956] ret_from_fork+0x2c/0x50
[ 22.852129] </TASK>
schedule_timeout()
->__mod_timer()
->get_target_base(base, timer->flags)
->get_timer_cpu_base(tflags, get_nohz_timer_target());
->cpu = get_nohz_timer_target()
->housekeeping_any_cpu(HK_TYPE_TIMER)
/*housekeeping.cpumasks[type] is 2-3*/
/*cpu_online_mask is 0-1*/
->cpu = cpumask_any_and(housekeeping.cpumasks[type],
cpu_online_mask);
/*cpu value is 4*/
->new_base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
/*new_base is illegal address*/
->if (base != new_base)
->raw_spin_lock(&new_base->lock); ==> trigger Oops
This commit therefore add checks for cpumask_any_and() return values
in housekeeping_any_cpu(), if cpumask_any_and() returns an illegal CPU
value, the housekeeping_any_cpu() will return current CPU number.
Signed-off-by: Zqiang <[email protected]>
---
kernel/sched/isolation.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 373d42c707bc..534397ab7a36 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -46,7 +46,11 @@ int housekeeping_any_cpu(enum hk_type type)
if (cpu < nr_cpu_ids)
return cpu;
- return cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
+ cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
+ if (cpu >= nr_cpu_ids)
+ return smp_processor_id();
+ else
+ return cpu;
}
}
return smp_processor_id();
--
2.25.1
Thanks for checking this!
On Fri, Feb 10, 2023 at 08:00:21AM +0800, Zqiang wrote:
> For kernels built with CONFIG_NO_HZ_FULL=y, running the following tests:
>
> runqemu kvm slirp nographic qemuparams="-m 1024 -smp 4" bootparams=
> "console=ttyS0 nohz_full=0,1 rcu_nocbs=0,1 sched_verbose" -d
Has this ever worked? Again I'm tempted to just:
git revert 08ae95f4fd3b38b257f5dc7e6507e071c27ba0d5
>
> root@qemux86-64:~# echo 0 > /sys/devices/system/cpu/cpu2/online
> root@qemux86-64:~# echo 0 > /sys/devices/system/cpu/cpu3/online
>
> [ 22.838290] BUG: unable to handle page fault for address: ffffffff84cd48c0
On Thu, Feb 9, 2023 at 6:55 PM Zqiang <[email protected]> wrote:
>
> For kernels built with CONFIG_NO_HZ_FULL=y, running the following tests:
>
[...]
> This commit therefore add checks for cpumask_any_and() return values
> in housekeeping_any_cpu(), if cpumask_any_and() returns an illegal CPU
> value, the housekeeping_any_cpu() will return current CPU number.
>
> Signed-off-by: Zqiang <[email protected]>
> ---
> kernel/sched/isolation.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 373d42c707bc..534397ab7a36 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -46,7 +46,11 @@ int housekeeping_any_cpu(enum hk_type type)
> if (cpu < nr_cpu_ids)
> return cpu;
>
> - return cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
> + cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
> + if (cpu >= nr_cpu_ids)
> + return smp_processor_id();
> + else
> + return cpu;
Nit: no need of "else", simply:
return (cpu >= nr_cpuids ? smp_processor_id() : cpu);
or
if (cpu >= nr_cpu_ids)
return smp_processor_id();
return cpu;
Thanks.
>
> For kernels built with CONFIG_NO_HZ_FULL=y, running the following tests:
>
[...]
> This commit therefore add checks for cpumask_any_and() return values
> in housekeeping_any_cpu(), if cpumask_any_and() returns an illegal CPU
> value, the housekeeping_any_cpu() will return current CPU number.
>
> Signed-off-by: Zqiang <[email protected]>
> ---
> kernel/sched/isolation.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 373d42c707bc..534397ab7a36 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -46,7 +46,11 @@ int housekeeping_any_cpu(enum hk_type type)
> if (cpu < nr_cpu_ids)
> return cpu;
>
> - return cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
> + cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask);
> + if (cpu >= nr_cpu_ids)
> + return smp_processor_id();
> + else
> + return cpu;
>
>Nit: no need of "else", simply:
>
>return (cpu >= nr_cpuids ? smp_processor_id() : cpu);
Thanks Joel, I have done the same modification in v3 version, and this change is
also related to a 08ae95f4fd3b, after revert it, this calltrace will disappear.
Thanks
Zqiang
>
>or
>
>if (cpu >= nr_cpu_ids)
> return smp_processor_id();
>return cpu;
>
>Thanks.