>
> On Mon, Jul 06, 2026 at 06:03:09PM +0800, Zqiang wrote:
>
> >
> > The RCU tasks trace has been reimplemented by 'commit c27cea4416a3
> > ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast")', the
> > rcu_tasks structure's->n_ipis_fails is no longer used, this commit
> > therefore remove it.
> >
> > Signed-off-by: Zqiang <[email protected]>
> >
> I have queued both for review and testing, thank you!
>
> This patch produced the expected result in my initial tests. However,
> for the second patch, I used this command to force a stall:
>
> tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 15
> --configs "TASKS01 TASKS02 TASKS03 RUDE01" --bootargs
> "rcutorture.stall_cpu=660" --trust-make
>
> Except I got vanilla RCU CPU stall warnings, but not RCU Tasks nor
> RCU Tasks Rude stall warnings. And not even the "grace period number"
> pre-stall message. Probably because I am forgetting something. But what
> did you do to test your change?
Hello, Paul
The rcutorture module use module_init() to load, however the
rcu_tasks_initiate_self_tests() is called in core_initcall(),
the core_initcall() have a higher priority than module_init().
This is possible, the RCU tasks test may have already completed,
but the rcutorture may have only just started.
so I use the following modifications to verify:
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index d9e1e53f4ccf..7e5ff5108cdd 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1489,7 +1489,6 @@ static void rcu_tasks_initiate_self_tests(void)
pr_info("Running RCU Tasks wait API self tests\n");
tests[0].runstart = jiffies;
synchronize_rcu_tasks();
- call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
#endif
#ifdef CONFIG_TASKS_RUDE_RCU
@@ -1555,6 +1554,7 @@ static void rcu_tasks_verify_work_fn(struct work_struct
*work __maybe_unused)
static int rcu_tasks_verify_schedule_work(void)
{
INIT_DELAYED_WORK(&rcu_tasks_verify_work, rcu_tasks_verify_work_fn);
+ call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
rcu_tasks_verify_work_fn(NULL);
return 0;
}
Run qemu with bootparams="rcutorture.torture_type=srcu
rcutorture.stall_cpu=800 rcutorture.stall_cpu_block=1
rcutorture.stall_no_softlockup=1 rcupdate.rcu_tasks_lazy_ms=120000"
[ 30.826022] call_rcu_tasks() has failed boot-time tests.
[ 30.826790] rcu_tasks: RTGS_WAIT_CBS(11) since 7596 g:4 i:0 kCuU l:30000
[ 30.827424] ------------[ cut here ]------------
[ 30.827862] WARNING: kernel/rcu/tasks.h:1533 at
rcu_tasks_verify_self_tests+0xa7/0xc0, CPU#1: kworker/1:1/79
[ 30.828717] Modules linked in:
[ 30.829144] CPU: 1 UID: 0 PID: 79 Comm: kworker/1:1 Tainted: G W
7.1.0-rc4+ #25 PREEMPT(lazy) e641c8af833b714510f82b4c2bc5dbbb1ef1e911
[ 30.830176] Tainted: [W]=WARN
[ 30.830468] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 30.831326] Workqueue: events rcu_tasks_verify_work_fn
....
[ 722.218096] INFO: rcu_tasks detected stalls on tasks:
[ 722.218689] 0000000095041800: .. nvcsw: 2/2 holdout: 1 idle_cpu: -1/7
[ 722.219308] task:rcu_torture_sta state:R running task stack:0
pid:122 tgid:122 ppid:2 task_flags:0x208040 flags:0x00080000
[ 722.220442] Call Trace:
[ 722.220744] <TASK>
[ 722.221035] __schedule+0x2e9/0x1460
[ 722.221449] ? preempt_schedule+0x30/0x40
[ 722.221895] preempt_schedule_common+0x24/0x90
[ 722.222432] preempt_schedule+0x30/0x40
[ 722.222842] rcu_torture_stall+0x266/0x430
[ 722.223286] ? __kthread_parkme+0x8f/0xe0
[ 722.223735] ? __pfx_rcu_torture_stall+0x10/0x10
[ 722.224226] kthread+0x13d/0x180
[ 722.224600] ? __pfx_kthread+0x10/0x10
[ 722.224996] ret_from_fork+0x29d/0x3b0
[ 722.225669] ? __pfx_kthread+0x10/0x10
[ 722.226131] ret_from_fork_asm+0x1a/0x30
[ 722.226668] </TASK>
Thanks
Zqiang
>
> Thanx, Paul
>
> >
> > ---
> > kernel/rcu/tasks.h | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > index f4da5fad70f5..7f7d1e636217 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -67,7 +67,6 @@ struct rcu_tasks_percpu {
> > * @gp_start: Most recent grace-period start in jiffies.
> > * @tasks_gp_seq: Number of grace periods completed since boot in upper
> > bits.
> > * @n_ipis: Number of IPIs sent to encourage grace periods to end.
> > - * @n_ipis_fails: Number of IPI-send failures.
> > * @kthread_ptr: This flavor's grace-period/callback-invocation kthread.
> > * @lazy_jiffies: Number of jiffies to allow callbacks to be lazy.
> > * @pregp_func: This flavor's pre-grace-period function (optional).
> > @@ -102,7 +101,6 @@ struct rcu_tasks {
> > unsigned long gp_start;
> > unsigned long tasks_gp_seq;
> > unsigned long n_ipis;
> > - unsigned long n_ipis_fails;
> > struct task_struct *kthread_ptr;
> > unsigned long lazy_jiffies;
> > rcu_tasks_gp_func_t gp_func;
> > @@ -735,12 +733,12 @@ static void show_rcu_tasks_generic_gp_kthread(struct
> > rcu_tasks *rtp, char *s)
> > if (havecbs && haveurgent && haveurgentcbs)
> > break;
> > }
> > - pr_info("%s: %s(%d) since %lu g:%lu i:%lu/%lu %c%c%c%c l:%lu %s\n",
> > + pr_info("%s: %s(%d) since %lu g:%lu i:%lu %c%c%c%c l:%lu %s\n",
> > rtp->kname,
> > tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
> > jiffies - data_race(rtp->gp_jiffies),
> > data_race(rcu_seq_current(&rtp->tasks_gp_seq)),
> > - data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
> > + data_race(rtp->n_ipis),
> > ".k"[!!data_race(rtp->kthread_ptr)],
> > ".C"[havecbs],
> > ".u"[haveurgent],
> > --
> > 2.17.1
> >
>
