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Commit 75c27f11 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Remove CONFIG_RCU_CPU_STALL_INFO 



The CONFIG_RCU_CPU_STALL_INFO has been default-y for a couple of
releases with no complaints, so it is time to eliminate this Kconfig
option entirely, so that the long-form RCU CPU stall warnings cannot
be disabled.  This commit does just that.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 9b683874

Documentation/RCU/stallwarn.txt

+2 −10
Original line number Diff line number Diff line
@@ -26,12 +26,6 @@ CONFIG_RCU_CPU_STALL_TIMEOUT 
	Stall-warning messages may be enabled and disabled completely via

	/sys/module/rcupdate/parameters/rcu_cpu_stall_suppress.



CONFIG_RCU_CPU_STALL_INFO



	This kernel configuration parameter causes the stall warning to

	print out additional per-CPU diagnostic information, including

	information on scheduling-clock ticks and RCU's idle-CPU tracking.



RCU_STALL_DELAY_DELTA



	Although the lockdep facility is extremely useful, it does add
@@ -101,15 +95,13 @@ interact. Please note that it is not possible to entirely eliminate this 
sort of false positive without resorting to things like stop_machine(),

which is overkill for this sort of problem.



If the CONFIG_RCU_CPU_STALL_INFO kernel configuration parameter is set,

more information is printed with the stall-warning message, for example:

Recent kernels will print a long form of the stall-warning message:



	INFO: rcu_preempt detected stall on CPU

	0: (63959 ticks this GP) idle=241/3fffffffffffffff/0 softirq=82/543

	   (t=65000 jiffies)



In kernels with CONFIG_RCU_FAST_NO_HZ, even more information is

printed:

In kernels with CONFIG_RCU_FAST_NO_HZ, more information is printed:



	INFO: rcu_preempt detected stall on CPU

	0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 nonlazy_posted: 25 .D

kernel/rcu/tree.h

+0 −4
Original line number Diff line number Diff line
@@ -288,12 +288,10 @@ struct rcu_data { 
	bool		gpwrap;		/* Possible gpnum/completed wrap. */

	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */

	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */

#ifdef CONFIG_RCU_CPU_STALL_INFO

	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */

					/*  ticks this CPU has handled */

					/*  during and after the last grace */

					/* period it is aware of. */

#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */



	/* 2) batch handling */

	/*
@@ -388,9 +386,7 @@ struct rcu_data { 
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */



	/* 8) RCU CPU stall data. */

#ifdef CONFIG_RCU_CPU_STALL_INFO

	unsigned int softirq_snap;	/* Snapshot of softirq activity. */

#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */



	int cpu;

	struct rcu_state *rsp;

kernel/rcu/tree_plugin.h

+0 −45
Original line number Diff line number Diff line
@@ -82,8 +82,6 @@ static void __init rcu_bootup_announce_oddness(void) 
		pr_info("\tRCU lockdep checking is enabled.\n");

	if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_RUNNABLE))

		pr_info("\tRCU torture testing starts during boot.\n");

	if (IS_ENABLED(CONFIG_RCU_CPU_STALL_INFO))

		pr_info("\tAdditional per-CPU info printed with stalls.\n");

	if (RCU_NUM_LVLS >= 4)

		pr_info("\tFour(or more)-level hierarchy is enabled.\n");

	if (RCU_FANOUT_LEAF != 16)
@@ -418,8 +416,6 @@ static void rcu_print_detail_task_stall(struct rcu_state *rsp) 
		rcu_print_detail_task_stall_rnp(rnp);

}



#ifdef CONFIG_RCU_CPU_STALL_INFO



static void rcu_print_task_stall_begin(struct rcu_node *rnp)

{

	pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
@@ -431,18 +427,6 @@ static void rcu_print_task_stall_end(void) 
	pr_cont("\n");

}



#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */



static void rcu_print_task_stall_begin(struct rcu_node *rnp)

{

}



static void rcu_print_task_stall_end(void)

{

}



#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */



/*

 * Scan the current list of tasks blocked within RCU read-side critical

 * sections, printing out the tid of each.
@@ -1685,8 +1669,6 @@ early_initcall(rcu_register_oom_notifier); 


#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */



#ifdef CONFIG_RCU_CPU_STALL_INFO



#ifdef CONFIG_RCU_FAST_NO_HZ



static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
@@ -1775,33 +1757,6 @@ static void increment_cpu_stall_ticks(void) 
		raw_cpu_inc(rsp->rda->ticks_this_gp);

}



#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */



static void print_cpu_stall_info_begin(void)

{

	pr_cont(" {");

}



static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)

{

	pr_cont(" %d", cpu);

}



static void print_cpu_stall_info_end(void)

{

	pr_cont("} ");

}



static void zero_cpu_stall_ticks(struct rcu_data *rdp)

{

}



static void increment_cpu_stall_ticks(void)

{

}



#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */



#ifdef CONFIG_RCU_NOCB_CPU



/*

lib/Kconfig.debug

+0 −14
Original line number Diff line number Diff line
@@ -1353,20 +1353,6 @@ config RCU_CPU_STALL_TIMEOUT 
	  RCU grace period persists, additional CPU stall warnings are

	  printed at more widely spaced intervals.



config RCU_CPU_STALL_INFO

	bool "Print additional diagnostics on RCU CPU stall"

	depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL

	default y

	help

	  For each stalled CPU that is aware of the current RCU grace

	  period, print out additional per-CPU diagnostic information

	  regarding scheduling-clock ticks, idle state, and,

	  for RCU_FAST_NO_HZ kernels, idle-entry state.



	  Say N if you are unsure.



	  Say Y if you want to enable such diagnostics.



config RCU_TRACE

	bool "Enable tracing for RCU"

	depends on DEBUG_KERNEL

tools/testing/selftests/rcutorture/configs/rcu/TREE01

+0 −1
Original line number Diff line number Diff line
@@ -13,7 +13,6 @@ CONFIG_MAXSMP=y 
CONFIG_RCU_NOCB_CPU=y

CONFIG_RCU_NOCB_CPU_ZERO=y

CONFIG_DEBUG_LOCK_ALLOC=n

CONFIG_RCU_CPU_STALL_INFO=n

CONFIG_RCU_BOOST=n

CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

CONFIG_RCU_EXPERT=y