* [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code
@ 2022-10-13 4:41 Zqiang
2022-10-13 14:13 ` Paul E. McKenney
2022-10-13 15:39 ` Joel Fernandes
0 siblings, 2 replies; 4+ messages in thread
From: Zqiang @ 2022-10-13 4:41 UTC (permalink / raw)
To: paulmck, frederic, quic_neeraju, joel; +Cc: rcu, linux-kernel
BUG: using __this_cpu_read() in preemptible [00000000]
code: rcu_torture_fqs/398
caller is __this_cpu_preempt_check+0x13/0x20
CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x86
dump_stack+0x10/0x16
check_preemption_disabled+0xe5/0xf0
__this_cpu_preempt_check+0x13/0x20
rcu_force_quiescent_state.part.0+0x1c/0x170
rcu_force_quiescent_state+0x1e/0x30
rcu_torture_fqs+0xca/0x160
? rcu_torture_boost+0x430/0x430
kthread+0x192/0x1d0
? kthread_complete_and_exit+0x30/0x30
ret_from_fork+0x22/0x30
</TASK>
When enable rcutorture.fqs_duration, the rcu_force_quiescent_state() be
invoked in rcu_torture_fqs task context, invoke __this_cpu_read() in
preemptible code section will trigger the above calltrace.
This commit convert __this_cpu_read() to raw_cpu_read() to avoid
this warning.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 96d678c9cfb6..282002e62cf3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2436,7 +2436,7 @@ void rcu_force_quiescent_state(void)
struct rcu_node *rnp_old = NULL;
/* Funnel through hierarchy to reduce memory contention. */
- rnp = __this_cpu_read(rcu_data.mynode);
+ rnp = raw_cpu_read(rcu_data.mynode);
for (; rnp != NULL; rnp = rnp->parent) {
ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
!raw_spin_trylock(&rnp->fqslock);
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code
2022-10-13 4:41 [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code Zqiang
@ 2022-10-13 14:13 ` Paul E. McKenney
2022-10-13 15:39 ` Joel Fernandes
1 sibling, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2022-10-13 14:13 UTC (permalink / raw)
To: Zqiang; +Cc: frederic, quic_neeraju, joel, rcu, linux-kernel
On Thu, Oct 13, 2022 at 12:41:48PM +0800, Zqiang wrote:
> BUG: using __this_cpu_read() in preemptible [00000000]
> code: rcu_torture_fqs/398
> caller is __this_cpu_preempt_check+0x13/0x20
> CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
> Call Trace:
> <TASK>
> dump_stack_lvl+0x5b/0x86
> dump_stack+0x10/0x16
> check_preemption_disabled+0xe5/0xf0
> __this_cpu_preempt_check+0x13/0x20
> rcu_force_quiescent_state.part.0+0x1c/0x170
> rcu_force_quiescent_state+0x1e/0x30
> rcu_torture_fqs+0xca/0x160
> ? rcu_torture_boost+0x430/0x430
> kthread+0x192/0x1d0
> ? kthread_complete_and_exit+0x30/0x30
> ret_from_fork+0x22/0x30
> </TASK>
>
> When enable rcutorture.fqs_duration, the rcu_force_quiescent_state() be
> invoked in rcu_torture_fqs task context, invoke __this_cpu_read() in
> preemptible code section will trigger the above calltrace.
>
> This commit convert __this_cpu_read() to raw_cpu_read() to avoid
> this warning.
>
> Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Good eyes! Queued, thank you!
Thanx, Paul
> ---
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 96d678c9cfb6..282002e62cf3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2436,7 +2436,7 @@ void rcu_force_quiescent_state(void)
> struct rcu_node *rnp_old = NULL;
>
> /* Funnel through hierarchy to reduce memory contention. */
> - rnp = __this_cpu_read(rcu_data.mynode);
> + rnp = raw_cpu_read(rcu_data.mynode);
> for (; rnp != NULL; rnp = rnp->parent) {
> ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
> !raw_spin_trylock(&rnp->fqslock);
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code
2022-10-13 4:41 [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code Zqiang
2022-10-13 14:13 ` Paul E. McKenney
@ 2022-10-13 15:39 ` Joel Fernandes
2022-10-14 14:38 ` Paul E. McKenney
1 sibling, 1 reply; 4+ messages in thread
From: Joel Fernandes @ 2022-10-13 15:39 UTC (permalink / raw)
To: Zqiang; +Cc: paulmck, frederic, quic_neeraju, rcu, linux-kernel
On Thu, Oct 13, 2022 at 12:41:48PM +0800, Zqiang wrote:
> BUG: using __this_cpu_read() in preemptible [00000000]
> code: rcu_torture_fqs/398
> caller is __this_cpu_preempt_check+0x13/0x20
> CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
> Call Trace:
> <TASK>
> dump_stack_lvl+0x5b/0x86
> dump_stack+0x10/0x16
> check_preemption_disabled+0xe5/0xf0
> __this_cpu_preempt_check+0x13/0x20
> rcu_force_quiescent_state.part.0+0x1c/0x170
> rcu_force_quiescent_state+0x1e/0x30
> rcu_torture_fqs+0xca/0x160
> ? rcu_torture_boost+0x430/0x430
> kthread+0x192/0x1d0
> ? kthread_complete_and_exit+0x30/0x30
> ret_from_fork+0x22/0x30
> </TASK>
>
> When enable rcutorture.fqs_duration, the rcu_force_quiescent_state() be
> invoked in rcu_torture_fqs task context, invoke __this_cpu_read() in
> preemptible code section will trigger the above calltrace.
Makes sense, so in theory the GP thread might get migrated after sampling
rcu_data.mynode but that's Ok since it wont change the behavior of the code
following it AFAICS.
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
thanks,
- Joel
> This commit convert __this_cpu_read() to raw_cpu_read() to avoid
> this warning.
>
> Signed-off-by: Zqiang <qiang1.zhang@intel.com>
> ---
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 96d678c9cfb6..282002e62cf3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2436,7 +2436,7 @@ void rcu_force_quiescent_state(void)
> struct rcu_node *rnp_old = NULL;
>
> /* Funnel through hierarchy to reduce memory contention. */
> - rnp = __this_cpu_read(rcu_data.mynode);
> + rnp = raw_cpu_read(rcu_data.mynode);
> for (; rnp != NULL; rnp = rnp->parent) {
> ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
> !raw_spin_trylock(&rnp->fqslock);
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code
2022-10-13 15:39 ` Joel Fernandes
@ 2022-10-14 14:38 ` Paul E. McKenney
0 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2022-10-14 14:38 UTC (permalink / raw)
To: Joel Fernandes; +Cc: Zqiang, frederic, quic_neeraju, rcu, linux-kernel
On Thu, Oct 13, 2022 at 03:39:45PM +0000, Joel Fernandes wrote:
> On Thu, Oct 13, 2022 at 12:41:48PM +0800, Zqiang wrote:
> > BUG: using __this_cpu_read() in preemptible [00000000]
> > code: rcu_torture_fqs/398
> > caller is __this_cpu_preempt_check+0x13/0x20
> > CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x5b/0x86
> > dump_stack+0x10/0x16
> > check_preemption_disabled+0xe5/0xf0
> > __this_cpu_preempt_check+0x13/0x20
> > rcu_force_quiescent_state.part.0+0x1c/0x170
> > rcu_force_quiescent_state+0x1e/0x30
> > rcu_torture_fqs+0xca/0x160
> > ? rcu_torture_boost+0x430/0x430
> > kthread+0x192/0x1d0
> > ? kthread_complete_and_exit+0x30/0x30
> > ret_from_fork+0x22/0x30
> > </TASK>
> >
> > When enable rcutorture.fqs_duration, the rcu_force_quiescent_state() be
> > invoked in rcu_torture_fqs task context, invoke __this_cpu_read() in
> > preemptible code section will trigger the above calltrace.
>
> Makes sense, so in theory the GP thread might get migrated after sampling
> rcu_data.mynode but that's Ok since it wont change the behavior of the code
> following it AFAICS.
>
> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Thank you! I will apply this on the next rebase.
Thanx, Paul
> thanks,
>
> - Joel
>
> > This commit convert __this_cpu_read() to raw_cpu_read() to avoid
> > this warning.
> >
> > Signed-off-by: Zqiang <qiang1.zhang@intel.com>
> > ---
> > kernel/rcu/tree.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 96d678c9cfb6..282002e62cf3 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -2436,7 +2436,7 @@ void rcu_force_quiescent_state(void)
> > struct rcu_node *rnp_old = NULL;
> >
> > /* Funnel through hierarchy to reduce memory contention. */
> > - rnp = __this_cpu_read(rcu_data.mynode);
> > + rnp = raw_cpu_read(rcu_data.mynode);
> > for (; rnp != NULL; rnp = rnp->parent) {
> > ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
> > !raw_spin_trylock(&rnp->fqslock);
> > --
> > 2.25.1
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-10-13 4:41 [PATCH] rcu: Fix use __this_cpu_read() warning in preemptible code Zqiang
2022-10-13 14:13 ` Paul E. McKenney
2022-10-13 15:39 ` Joel Fernandes
2022-10-14 14:38 ` Paul E. McKenney
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