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Commit 1ed509a2 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Add RCU_CPU_STALL_VERBOSE to dump detailed per-task information 



When RCU detects a grace-period stall, it currently just prints
out the PID of any tasks doing the stalling.  This patch adds
RCU_CPU_STALL_VERBOSE, which enables the more-verbose reporting
from sched_show_task().

Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-21-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6155fec9

kernel/rcutree.c

+4 −0
Original line number Original line Diff line number Diff line
@@ -489,6 +489,10 @@ static void print_other_cpu_stall(struct rcu_state *rsp) 
	       smp_processor_id(), (long)(jiffies - rsp->gp_start));

	       smp_processor_id(), (long)(jiffies - rsp->gp_start));

	trigger_all_cpu_backtrace();

	trigger_all_cpu_backtrace();





	/* If so configured, complain about tasks blocking the grace period. */



	rcu_print_detail_task_stall(rsp);



	force_quiescent_state(rsp, 0);  /* Kick them all. */

	force_quiescent_state(rsp, 0);  /* Kick them all. */

}

}

kernel/rcutree.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -352,6 +352,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, 
				      unsigned long flags);

				      unsigned long flags);

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

#endif /* #ifdef CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

static void rcu_print_detail_task_stall(struct rcu_state *rsp);

static void rcu_print_task_stall(struct rcu_node *rnp);

static void rcu_print_task_stall(struct rcu_node *rnp);

#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);

static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);

kernel/rcutree_plugin.h

+52 −0
Original line number Original line Diff line number Diff line
@@ -312,6 +312,50 @@ EXPORT_SYMBOL_GPL(__rcu_read_unlock); 




#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR





#ifdef CONFIG_RCU_CPU_STALL_VERBOSE



/*

 * Dump detailed information for all tasks blocking the current RCU

 * grace period on the specified rcu_node structure.

 */

static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)

{

	unsigned long flags;

	struct list_head *lp;

	int phase;

	struct task_struct *t;



	if (rcu_preempted_readers(rnp)) {

		raw_spin_lock_irqsave(&rnp->lock, flags);

		phase = rnp->gpnum & 0x1;

		lp = &rnp->blocked_tasks[phase];

		list_for_each_entry(t, lp, rcu_node_entry)

			sched_show_task(t);

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

	}

}



/*

 * Dump detailed information for all tasks blocking the current RCU

 * grace period.

 */

static void rcu_print_detail_task_stall(struct rcu_state *rsp)

{

	struct rcu_node *rnp = rcu_get_root(rsp);



	rcu_print_detail_task_stall_rnp(rnp);

	rcu_for_each_leaf_node(rsp, rnp)

		rcu_print_detail_task_stall_rnp(rnp);

}



#else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */



static void rcu_print_detail_task_stall(struct rcu_state *rsp)

{

}



#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */



/*

/*

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

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

 * sections, printing out the tid of each.

 * sections, printing out the tid of each.
@@ -760,6 +804,14 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) 




#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR





/*

 * Because preemptable RCU does not exist, we never have to check for

 * tasks blocked within RCU read-side critical sections.

 */

static void rcu_print_detail_task_stall(struct rcu_state *rsp)

{

}



/*

/*

 * Because preemptable RCU does not exist, we never have to check for

 * Because preemptable RCU does not exist, we never have to check for

 * tasks blocked within RCU read-side critical sections.

 * tasks blocked within RCU read-side critical sections.

lib/Kconfig.debug

+12 −0
Original line number Original line Diff line number Diff line
@@ -781,6 +781,18 @@ config RCU_CPU_STALL_DETECTOR 




	  Say Y if you are unsure.

	  Say Y if you are unsure.





config RCU_CPU_STALL_VERBOSE

	bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"

	depends on RCU_CPU_STALL_DETECTOR && TREE_PREEMPT_RCU

	default n

	help

	  This option causes RCU to printk detailed per-task information

	  for any tasks that are stalling the current RCU grace period.



	  Say N if you are unsure.



	  Say Y if you want to enable such checks.



config KPROBES_SANITY_TEST

config KPROBES_SANITY_TEST

	bool "Kprobes sanity tests"

	bool "Kprobes sanity tests"

	depends on DEBUG_KERNEL

	depends on DEBUG_KERNEL