From 844ccdd7dce2c1a6ea9b437fcf8c3265b136e4a5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 3 Oct 2017 16:51:47 -0700 Subject: [PATCH] rcu: Eliminate rcu_irq_enter_disabled() Now that the irq path uses the rcu_nmi_{enter,exit}() algorithm, rcu_irq_enter() and rcu_irq_exit() may be used from any context. There is thus no need for rcu_irq_enter_disabled() and for the checks using it. This commit therefore eliminates rcu_irq_enter_disabled(). Signed-off-by: Paul E. McKenney --- include/linux/rcutiny.h | 1 - include/linux/rcutree.h | 1 - include/linux/tracepoint.h | 5 +---- kernel/rcu/tree.c | 22 ++-------------------- kernel/trace/trace.c | 11 ----------- 5 files changed, 3 insertions(+), 37 deletions(-) diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index b3dbf9502fd0..ce9beec35e34 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -111,7 +111,6 @@ static inline void rcu_cpu_stall_reset(void) { } static inline void rcu_idle_enter(void) { } static inline void rcu_idle_exit(void) { } static inline void rcu_irq_enter(void) { } -static inline bool rcu_irq_enter_disabled(void) { return false; } static inline void rcu_irq_exit_irqson(void) { } static inline void rcu_irq_enter_irqson(void) { } static inline void rcu_irq_exit(void) { } diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 37d6fd3b7ff8..fd996cdf1833 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -85,7 +85,6 @@ void rcu_irq_enter(void); void rcu_irq_exit(void); void rcu_irq_enter_irqson(void); void rcu_irq_exit_irqson(void); -bool rcu_irq_enter_disabled(void); void exit_rcu(void); diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index a26ffbe09e71..c94f466d57ef 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -137,11 +137,8 @@ extern void syscall_unregfunc(void); \ if (!(cond)) \ return; \ - if (rcucheck) { \ - if (WARN_ON_ONCE(rcu_irq_enter_disabled())) \ - return; \ + if (rcucheck) \ rcu_irq_enter_irqson(); \ - } \ rcu_read_lock_sched_notrace(); \ it_func_ptr = rcu_dereference_sched((tp)->funcs); \ if (it_func_ptr) { \ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d123474fe829..444aa2b3f24d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -270,20 +270,6 @@ static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), }; -/* - * There's a few places, currently just in the tracing infrastructure, - * that uses rcu_irq_enter() to make sure RCU is watching. But there's - * a small location where that will not even work. In those cases - * rcu_irq_enter_disabled() needs to be checked to make sure rcu_irq_enter() - * can be called. - */ -static DEFINE_PER_CPU(bool, disable_rcu_irq_enter); - -bool rcu_irq_enter_disabled(void) -{ - return this_cpu_read(disable_rcu_irq_enter); -} - /* * Record entry into an extended quiescent state. This is only to be * called when not already in an extended quiescent state. @@ -792,10 +778,8 @@ static void rcu_eqs_enter_common(bool user) do_nocb_deferred_wakeup(rdp); } rcu_prepare_for_idle(); - __this_cpu_inc(disable_rcu_irq_enter); - rdtp->dynticks_nesting = 0; /* Breaks tracing momentarily. */ - rcu_dynticks_eqs_enter(); /* After this, tracing works again. */ - __this_cpu_dec(disable_rcu_irq_enter); + rdtp->dynticks_nesting = 0; + rcu_dynticks_eqs_enter(); rcu_dynticks_task_enter(); /* @@ -1001,10 +985,8 @@ static void rcu_eqs_exit(bool user) if (oldval) { rdtp->dynticks_nesting++; } else { - __this_cpu_inc(disable_rcu_irq_enter); rcu_eqs_exit_common(1, user); rdtp->dynticks_nesting = 1; - __this_cpu_dec(disable_rcu_irq_enter); WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); } } diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 73e67b68c53b..dbce1be3bab8 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2682,17 +2682,6 @@ void __trace_stack(struct trace_array *tr, unsigned long flags, int skip, if (unlikely(in_nmi())) return; - /* - * It is possible that a function is being traced in a - * location that RCU is not watching. A call to - * rcu_irq_enter() will make sure that it is, but there's - * a few internal rcu functions that could be traced - * where that wont work either. In those cases, we just - * do nothing. - */ - if (unlikely(rcu_irq_enter_disabled())) - return; - rcu_irq_enter_irqson(); __ftrace_trace_stack(buffer, flags, skip, pc, NULL); rcu_irq_exit_irqson();