| Message ID | 20221013044148.2894320-1-qiang1.zhang@intel.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f965c827ea36521a2145b538660fe64237ab4a96 |
| Headers | show |
| Series | rcu: Fix use __this_cpu_read() warning in preemptible code | expand |
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 >
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 >
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 > >
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);
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(-)