| Message ID | 1315332049-2604-41-git-send-email-paulmck@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Sep 06, 2011 at 11:00:35AM -0700, Paul E. McKenney wrote: > From: Paul E. McKenney <paul.mckenney@linaro.org> > > Create a separate lockdep class for the rt_mutex used for RCU priority > boosting and enable use of rt_mutex_lock() with irqs disabled. This > prevents RCU priority boosting from falling prey to deadlocks when > someone begins an RCU read-side critical section in preemptible state, > but releases it with an irq-disabled lock held. > > Unfortunately, the scheduler's runqueue and priority-inheritance locks > still must either completely enclose or be completely enclosed by any > overlapping RCU read-side critical section. > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > kernel/rcutree_plugin.h | 6 ++++++ > kernel/rtmutex.c | 8 ++++++++ > 2 files changed, 14 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index d3127e8..f6c63ea 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -1149,6 +1149,8 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp) > > #endif /* #else #ifdef CONFIG_RCU_TRACE */ > > +static struct lock_class_key rcu_boost_class; > + > /* > * Carry out RCU priority boosting on the task indicated by ->exp_tasks > * or ->boost_tasks, advancing the pointer to the next task in the > @@ -1211,10 +1213,14 @@ static int rcu_boost(struct rcu_node *rnp) > */ > t = container_of(tb, struct task_struct, rcu_node_entry); > rt_mutex_init_proxy_locked(&mtx, t); > + /* Avoid lockdep false positives. This rt_mutex is its own thing. */ > + lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class, > + "rcu_boost_mutex"); > t->rcu_boost_mutex = &mtx; raw_spin_unlock_irqrestore(&rnp->lock, flags); <====A > rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ > + local_irq_restore(flags); Does it help here? irq is enabled at A. So we still call rt_mutex_lock() with irq enabled. Seems should s/raw_spin_unlock_irqrestore/raw_spin_unlock ? BTW, since we are in process context, 'flags' is not needed to save, no? Thanks, Yong > > return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL; > } > diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c > index ab44911..2548f44 100644 > --- a/kernel/rtmutex.c > +++ b/kernel/rtmutex.c > @@ -579,6 +579,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, > struct rt_mutex_waiter *waiter) > { > int ret = 0; > + int was_disabled; > > for (;;) { > /* Try to acquire the lock: */ > @@ -601,10 +602,17 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, > > raw_spin_unlock(&lock->wait_lock); > > + was_disabled = irqs_disabled(); > + if (was_disabled) > + local_irq_enable(); > + > debug_rt_mutex_print_deadlock(waiter); > > schedule_rt_mutex(lock); > > + if (was_disabled) > + local_irq_disable(); > + > raw_spin_lock(&lock->wait_lock); > set_current_state(state); > } > -- > 1.7.3.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Sun, Sep 18, 2011 at 12:09:23PM +0800, Yong Zhang wrote: > On Tue, Sep 06, 2011 at 11:00:35AM -0700, Paul E. McKenney wrote: > > From: Paul E. McKenney <paul.mckenney@linaro.org> > > > > Create a separate lockdep class for the rt_mutex used for RCU priority > > boosting and enable use of rt_mutex_lock() with irqs disabled. This > > prevents RCU priority boosting from falling prey to deadlocks when > > someone begins an RCU read-side critical section in preemptible state, > > but releases it with an irq-disabled lock held. > > > > Unfortunately, the scheduler's runqueue and priority-inheritance locks > > still must either completely enclose or be completely enclosed by any > > overlapping RCU read-side critical section. > > > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > --- > > kernel/rcutree_plugin.h | 6 ++++++ > > kernel/rtmutex.c | 8 ++++++++ > > 2 files changed, 14 insertions(+), 0 deletions(-) > > > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > index d3127e8..f6c63ea 100644 > > --- a/kernel/rcutree_plugin.h > > +++ b/kernel/rcutree_plugin.h > > @@ -1149,6 +1149,8 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp) > > > > #endif /* #else #ifdef CONFIG_RCU_TRACE */ > > > > +static struct lock_class_key rcu_boost_class; > > + > > /* > > * Carry out RCU priority boosting on the task indicated by ->exp_tasks > > * or ->boost_tasks, advancing the pointer to the next task in the > > @@ -1211,10 +1213,14 @@ static int rcu_boost(struct rcu_node *rnp) > > */ > > t = container_of(tb, struct task_struct, rcu_node_entry); > > rt_mutex_init_proxy_locked(&mtx, t); > > + /* Avoid lockdep false positives. This rt_mutex is its own thing. */ > > + lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class, > > + "rcu_boost_mutex"); > > t->rcu_boost_mutex = &mtx; > > raw_spin_unlock_irqrestore(&rnp->lock, flags); <====A > > > rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ > > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ > > + local_irq_restore(flags); > > Does it help here? > irq is enabled at A. So we still call rt_mutex_lock() with irq enabled. > > Seems should s/raw_spin_unlock_irqrestore/raw_spin_unlock ? Hmmm... The above works at least by accident, but I am clearly not testing calling rt_mutex_lock(&mtx) and rt_mutex_unlock(&mtx) with interrupts disabled anywhere near as heavily as I thought I was. I will fix this one way or the other. > BTW, since we are in process context, 'flags' is not needed to save, > no? Only until the code gets moved/reused... Thanx, Paul > Thanks, > Yong > > > > > > return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL; > > } > > diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c > > index ab44911..2548f44 100644 > > --- a/kernel/rtmutex.c > > +++ b/kernel/rtmutex.c > > @@ -579,6 +579,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, > > struct rt_mutex_waiter *waiter) > > { > > int ret = 0; > > + int was_disabled; > > > > for (;;) { > > /* Try to acquire the lock: */ > > @@ -601,10 +602,17 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, > > > > raw_spin_unlock(&lock->wait_lock); > > > > + was_disabled = irqs_disabled(); > > + if (was_disabled) > > + local_irq_enable(); > > + > > debug_rt_mutex_print_deadlock(waiter); > > > > schedule_rt_mutex(lock); > > > > + if (was_disabled) > > + local_irq_disable(); > > + > > raw_spin_lock(&lock->wait_lock); > > set_current_state(state); > > } > > -- > > 1.7.3.2 > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index d3127e8..f6c63ea 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1149,6 +1149,8 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp) #endif /* #else #ifdef CONFIG_RCU_TRACE */ +static struct lock_class_key rcu_boost_class; + /* * Carry out RCU priority boosting on the task indicated by ->exp_tasks * or ->boost_tasks, advancing the pointer to the next task in the @@ -1211,10 +1213,14 @@ static int rcu_boost(struct rcu_node *rnp) */ t = container_of(tb, struct task_struct, rcu_node_entry); rt_mutex_init_proxy_locked(&mtx, t); + /* Avoid lockdep false positives. This rt_mutex is its own thing. */ + lockdep_set_class_and_name(&mtx.wait_lock, &rcu_boost_class, + "rcu_boost_mutex"); t->rcu_boost_mutex = &mtx; raw_spin_unlock_irqrestore(&rnp->lock, flags); rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ + local_irq_restore(flags); return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL; } diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index ab44911..2548f44 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -579,6 +579,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, struct rt_mutex_waiter *waiter) { int ret = 0; + int was_disabled; for (;;) { /* Try to acquire the lock: */ @@ -601,10 +602,17 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, raw_spin_unlock(&lock->wait_lock); + was_disabled = irqs_disabled(); + if (was_disabled) + local_irq_enable(); + debug_rt_mutex_print_deadlock(waiter); schedule_rt_mutex(lock); + if (was_disabled) + local_irq_disable(); + raw_spin_lock(&lock->wait_lock); set_current_state(state); }