| Message ID | 1346352988-32444-13-git-send-email-paulmck@linux.vnet.ibm.com |
|---|---|
| State | Accepted |
| Commit | 7a11e2058f02feb6884efb067f328012c318a13f |
| Headers | show |
On Thu, Aug 30, 2012 at 11:56:26AM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" <paul.mckenney@linaro.org> > > The use of raw_local_irq_save() is unnecessary, given that local_irq_save() > really does disable interrupts. Also, it appears to interfere with lockdep. > Therefore, this commit moves to local_irq_save(). It looks like the non-raw versions also include tracing, which typically has recursive dependency problems with RCU. Can all of these call sites safely call into tracing without recursing back into RCU? - Josh Triplett > Reported-by: Fengguang Wu <fengguang.wu@intel.com> > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Tested-by: Fengguang Wu <fengguang.wu@intel.com> > --- > kernel/rcutiny_plugin.h | 10 +++++----- > 1 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h > index 918fd1e..3d01902 100644 > --- a/kernel/rcutiny_plugin.h > +++ b/kernel/rcutiny_plugin.h > @@ -278,7 +278,7 @@ static int rcu_boost(void) > rcu_preempt_ctrlblk.exp_tasks == NULL) > return 0; /* Nothing to boost. */ > > - raw_local_irq_save(flags); > + local_irq_save(flags); > > /* > * Recheck with irqs disabled: all tasks in need of boosting > @@ -287,7 +287,7 @@ static int rcu_boost(void) > */ > if (rcu_preempt_ctrlblk.boost_tasks == NULL && > rcu_preempt_ctrlblk.exp_tasks == NULL) { > - raw_local_irq_restore(flags); > + local_irq_restore(flags); > return 0; > } > > @@ -317,7 +317,7 @@ static int rcu_boost(void) > t = container_of(tb, struct task_struct, rcu_node_entry); > rt_mutex_init_proxy_locked(&mtx, t); > t->rcu_boost_mutex = &mtx; > - raw_local_irq_restore(flags); > + local_irq_restore(flags); > rt_mutex_lock(&mtx); > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ > > @@ -991,9 +991,9 @@ static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) > { > unsigned long flags; > > - raw_local_irq_save(flags); > + local_irq_save(flags); > rcp->qlen -= n; > - raw_local_irq_restore(flags); > + local_irq_restore(flags); > } > > /* > -- > 1.7.8 >
On Fri, Aug 31, 2012 at 11:34:31AM -0700, Josh Triplett wrote: > On Thu, Aug 30, 2012 at 11:56:26AM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" <paul.mckenney@linaro.org> > > > > The use of raw_local_irq_save() is unnecessary, given that local_irq_save() > > really does disable interrupts. Also, it appears to interfere with lockdep. > > Therefore, this commit moves to local_irq_save(). > > It looks like the non-raw versions also include tracing, which typically > has recursive dependency problems with RCU. Can all of these call sites > safely call into tracing without recursing back into RCU? The rcu_trace_sub_qlen() version is the most suspicious, but it is the one that Fengguang found to be causing the problem: https://lkml.org/lkml/2012/8/21/551 Thanx, Paul > - Josh Triplett > > > Reported-by: Fengguang Wu <fengguang.wu@intel.com> > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Tested-by: Fengguang Wu <fengguang.wu@intel.com> > > --- > > kernel/rcutiny_plugin.h | 10 +++++----- > > 1 files changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h > > index 918fd1e..3d01902 100644 > > --- a/kernel/rcutiny_plugin.h > > +++ b/kernel/rcutiny_plugin.h > > @@ -278,7 +278,7 @@ static int rcu_boost(void) > > rcu_preempt_ctrlblk.exp_tasks == NULL) > > return 0; /* Nothing to boost. */ > > > > - raw_local_irq_save(flags); > > + local_irq_save(flags); > > > > /* > > * Recheck with irqs disabled: all tasks in need of boosting > > @@ -287,7 +287,7 @@ static int rcu_boost(void) > > */ > > if (rcu_preempt_ctrlblk.boost_tasks == NULL && > > rcu_preempt_ctrlblk.exp_tasks == NULL) { > > - raw_local_irq_restore(flags); > > + local_irq_restore(flags); > > return 0; > > } > > > > @@ -317,7 +317,7 @@ static int rcu_boost(void) > > t = container_of(tb, struct task_struct, rcu_node_entry); > > rt_mutex_init_proxy_locked(&mtx, t); > > t->rcu_boost_mutex = &mtx; > > - raw_local_irq_restore(flags); > > + local_irq_restore(flags); > > rt_mutex_lock(&mtx); > > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ > > > > @@ -991,9 +991,9 @@ static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) > > { > > unsigned long flags; > > > > - raw_local_irq_save(flags); > > + local_irq_save(flags); > > rcp->qlen -= n; > > - raw_local_irq_restore(flags); > > + local_irq_restore(flags); > > } > > > > /* > > -- > > 1.7.8 > > >
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 918fd1e..3d01902 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -278,7 +278,7 @@ static int rcu_boost(void) rcu_preempt_ctrlblk.exp_tasks == NULL) return 0; /* Nothing to boost. */ - raw_local_irq_save(flags); + local_irq_save(flags); /* * Recheck with irqs disabled: all tasks in need of boosting @@ -287,7 +287,7 @@ static int rcu_boost(void) */ if (rcu_preempt_ctrlblk.boost_tasks == NULL && rcu_preempt_ctrlblk.exp_tasks == NULL) { - raw_local_irq_restore(flags); + local_irq_restore(flags); return 0; } @@ -317,7 +317,7 @@ static int rcu_boost(void) t = container_of(tb, struct task_struct, rcu_node_entry); rt_mutex_init_proxy_locked(&mtx, t); t->rcu_boost_mutex = &mtx; - raw_local_irq_restore(flags); + local_irq_restore(flags); rt_mutex_lock(&mtx); rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ @@ -991,9 +991,9 @@ static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) { unsigned long flags; - raw_local_irq_save(flags); + local_irq_save(flags); rcp->qlen -= n; - raw_local_irq_restore(flags); + local_irq_restore(flags); } /*