From efeff6b39b9de4480572c7b0c5eb77204795cb57 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 5 Aug 2021 13:28:24 -0700 Subject: rcutorture: Warn on individual rcu_torture_init() error conditions When running rcutorture as a module, any rcu_torture_init() issues will be reflected in the error code from modprobe or insmod, as the case may be. However, these error codes are not available when running rcutorture built-in, for example, when using the kvm.sh script. This commit therefore adds WARN_ON_ONCE() to allow distinguishing rcu_torture_init() errors when running rcutorture built-in. Signed-off-by: Paul E. McKenney --- include/linux/torture.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include') diff --git a/include/linux/torture.h b/include/linux/torture.h index 0910c5803f35..24f58e50a94b 100644 --- a/include/linux/torture.h +++ b/include/linux/torture.h @@ -47,6 +47,14 @@ do { \ } while (0) void verbose_torout_sleep(void); +#define torture_init_error(firsterr) \ +({ \ + int ___firsterr = (firsterr); \ + \ + WARN_ONCE(!IS_MODULE(CONFIG_RCU_TORTURE_TEST) && ___firsterr < 0, "Torture-test initialization failed with error code %d\n", ___firsterr); \ + ___firsterr < 0; \ +}) + /* Definitions for online/offline exerciser. */ #ifdef CONFIG_HOTPLUG_CPU int torture_num_online_cpus(void); -- cgit v1.2.3 From a5c071ccfa1728508f31e61213ee795e4529d0d4 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 28 Jul 2021 12:28:27 -0700 Subject: rcu-tasks: Remove second argument of rcu_read_unlock_trace_special() The second argument of rcu_read_unlock_trace_special() is always zero. When called from exit_tasks_rcu_finish_trace(), it is the constant zero, and rcu_read_unlock_trace_special() doesn't get called from rcu_read_unlock_trace() unless the value of local variable "nesting" is zero because in that case the early return is taken instead. This commit therefore removes the "nesting" argument from the rcu_read_unlock_trace_special() function, substituting the constant zero within that function. This commit also adds a WARN_ON_ONCE() to rcu_read_lock_trace_held() in case non-zeroness some day appears. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate_trace.h | 5 +++-- kernel/rcu/tasks.h | 6 +++--- 2 files changed, 6 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h index 86c8f6c98412..6f9c35817398 100644 --- a/include/linux/rcupdate_trace.h +++ b/include/linux/rcupdate_trace.h @@ -31,7 +31,7 @@ static inline int rcu_read_lock_trace_held(void) #ifdef CONFIG_TASKS_TRACE_RCU -void rcu_read_unlock_trace_special(struct task_struct *t, int nesting); +void rcu_read_unlock_trace_special(struct task_struct *t); /** * rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section @@ -80,7 +80,8 @@ static inline void rcu_read_unlock_trace(void) WRITE_ONCE(t->trc_reader_nesting, nesting); return; // We assume shallow reader nesting. } - rcu_read_unlock_trace_special(t, nesting); + WARN_ON_ONCE(nesting != 0); + rcu_read_unlock_trace_special(t); } void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 8387e70e6b00..a3f4f9bd8c67 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -848,7 +848,7 @@ static void rcu_read_unlock_iw(struct irq_work *iwp) static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw); /* If we are the last reader, wake up the grace-period kthread. */ -void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) +void rcu_read_unlock_trace_special(struct task_struct *t) { int nq = READ_ONCE(t->trc_reader_special.b.need_qs); @@ -858,7 +858,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) // Update .need_qs before ->trc_reader_nesting for irq/NMI handlers. if (nq) WRITE_ONCE(t->trc_reader_special.b.need_qs, false); - WRITE_ONCE(t->trc_reader_nesting, nesting); + WRITE_ONCE(t->trc_reader_nesting, 0); if (nq && atomic_dec_and_test(&trc_n_readers_need_end)) irq_work_queue(&rcu_tasks_trace_iw); } @@ -1200,7 +1200,7 @@ static void exit_tasks_rcu_finish_trace(struct task_struct *t) WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting)); WRITE_ONCE(t->trc_reader_nesting, 0); if (WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs))) - rcu_read_unlock_trace_special(t, 0); + rcu_read_unlock_trace_special(t); } /** -- cgit v1.2.3 From 925da92ba5cb0c82d07cdd5049a07e40f54e9c44 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 26 Aug 2021 22:21:22 -0400 Subject: rcu: Avoid unneeded function call in rcu_read_unlock() Since commit aa40c138cc8f3 ("rcu: Report QS for outermost PREEMPT=n rcu_read_unlock() for strict GPs") the function rcu_read_unlock_strict() is invoked by the inlined rcu_read_unlock() function. However, rcu_read_unlock_strict() is an empty function in production kernels, which are built with CONFIG_RCU_STRICT_GRACE_PERIOD=n. There is a mention of rcu_read_unlock_strict() in the BPF verifier, but this is in a deny-list, meaning that BPF does not care whether rcu_read_unlock_strict() is ever called. This commit therefore provides a slight performance improvement by hoisting the check of CONFIG_RCU_STRICT_GRACE_PERIOD from rcu_read_unlock_strict() into rcu_read_unlock(), thus avoiding the pointless call to an empty function. Cc: Alexei Starovoitov Acked-by: Andrii Nakryiko Signed-off-by: Waiman Long Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 3 ++- kernel/rcu/tree_plugin.h | 3 +-- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 434d12fe2d4f..5e0beb5c5659 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -71,7 +71,8 @@ static inline void __rcu_read_lock(void) static inline void __rcu_read_unlock(void) { preempt_enable(); - rcu_read_unlock_strict(); + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + rcu_read_unlock_strict(); } static inline int rcu_preempt_depth(void) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index d070059163d7..1a6fdb03d0a5 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -814,8 +814,7 @@ void rcu_read_unlock_strict(void) { struct rcu_data *rdp; - if (!IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) || - irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) + if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) return; rdp = this_cpu_ptr(&rcu_data); rcu_report_qs_rdp(rdp); -- cgit v1.2.3