Commit ad0dc7f9 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Add forward-progress checking for writer 



The rcutorture output currently does not distinguish between stalls in
the RCU implementation and stalls in the rcu_torture_writer() kthreads.
This commit therefore adds some diagnostics to help distinguish between
these two conditions, at least for the non-SRCU implementations.  (SRCU
does not provide evidence of update-side forward progress by design.)

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent c9eaa447

include/linux/rcupdate.h

+19 −0
Original line number Diff line number Diff line
@@ -51,7 +51,17 @@ extern int rcu_expedited; /* for sysctl */ 
extern int rcutorture_runnable; /* for sysctl */

#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */



enum rcutorture_type {

	RCU_FLAVOR,

	RCU_BH_FLAVOR,

	RCU_SCHED_FLAVOR,

	SRCU_FLAVOR,

	INVALID_RCU_FLAVOR

};



#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)

void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,

			    unsigned long *gpnum, unsigned long *completed);

void rcutorture_record_test_transition(void);

void rcutorture_record_progress(unsigned long vernum);

void do_trace_rcu_torture_read(const char *rcutorturename,
@@ -60,6 +70,15 @@ void do_trace_rcu_torture_read(const char *rcutorturename, 
			       unsigned long c_old,

			       unsigned long c);

#else

static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,

					  int *flags,

					  unsigned long *gpnum,

					  unsigned long *completed)

{

	*flags = 0;

	*gpnum = 0;

	*completed = 0;

}

static inline void rcutorture_record_test_transition(void)

{

}

kernel/rcu/rcutorture.c

+37 −0
Original line number Diff line number Diff line
@@ -138,6 +138,15 @@ static long n_barrier_attempts; 
static long n_barrier_successes;

static struct list_head rcu_torture_removed;



static int rcu_torture_writer_state;

#define RTWS_FIXED_DELAY	0

#define RTWS_DELAY		1

#define RTWS_REPLACE		2

#define RTWS_DEF_FREE		3

#define RTWS_EXP_SYNC		4

#define RTWS_STUTTER		5

#define RTWS_STOPPING		6



#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)

#define RCUTORTURE_RUNNABLE_INIT 1

#else
@@ -214,6 +223,7 @@ rcu_torture_free(struct rcu_torture *p) 
 */



struct rcu_torture_ops {

	int ttype;

	void (*init)(void);

	int (*readlock)(void);

	void (*read_delay)(struct torture_random_state *rrsp);
@@ -312,6 +322,7 @@ static void rcu_sync_torture_init(void) 
}



static struct rcu_torture_ops rcu_ops = {

	.ttype		= RCU_FLAVOR,

	.init		= rcu_sync_torture_init,

	.readlock	= rcu_torture_read_lock,

	.read_delay	= rcu_read_delay,
@@ -355,6 +366,7 @@ static void rcu_bh_torture_deferred_free(struct rcu_torture *p) 
}



static struct rcu_torture_ops rcu_bh_ops = {

	.ttype		= RCU_BH_FLAVOR,

	.init		= rcu_sync_torture_init,

	.readlock	= rcu_bh_torture_read_lock,

	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
@@ -397,6 +409,7 @@ call_rcu_busted(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) 
}



static struct rcu_torture_ops rcu_busted_ops = {

	.ttype		= INVALID_RCU_FLAVOR,

	.init		= rcu_sync_torture_init,

	.readlock	= rcu_torture_read_lock,

	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
@@ -492,6 +505,7 @@ static void srcu_torture_synchronize_expedited(void) 
}



static struct rcu_torture_ops srcu_ops = {

	.ttype		= SRCU_FLAVOR,

	.init		= rcu_sync_torture_init,

	.readlock	= srcu_torture_read_lock,

	.read_delay	= srcu_read_delay,
@@ -527,6 +541,7 @@ static void rcu_sched_torture_deferred_free(struct rcu_torture *p) 
}



static struct rcu_torture_ops sched_ops = {

	.ttype		= RCU_SCHED_FLAVOR,

	.init		= rcu_sync_torture_init,

	.readlock	= sched_torture_read_lock,

	.read_delay	= rcu_read_delay,  /* just reuse rcu's version. */
@@ -699,12 +714,15 @@ rcu_torture_writer(void *arg) 
	set_user_nice(current, MAX_NICE);



	do {

		rcu_torture_writer_state = RTWS_FIXED_DELAY;

		schedule_timeout_uninterruptible(1);

		rp = rcu_torture_alloc();

		if (rp == NULL)

			continue;

		rp->rtort_pipe_count = 0;

		rcu_torture_writer_state = RTWS_DELAY;

		udelay(torture_random(&rand) & 0x3ff);

		rcu_torture_writer_state = RTWS_REPLACE;

		old_rp = rcu_dereference_check(rcu_torture_current,

					       current == writer_task);

		rp->rtort_mbtest = 1;
@@ -721,8 +739,10 @@ rcu_torture_writer(void *arg) 
			else

				exp = gp_exp;

			if (!exp) {

				rcu_torture_writer_state = RTWS_DEF_FREE;

				cur_ops->deferred_free(old_rp);

			} else {

				rcu_torture_writer_state = RTWS_EXP_SYNC;

				cur_ops->exp_sync();

				list_add(&old_rp->rtort_free,

					 &rcu_torture_removed);
@@ -743,8 +763,10 @@ rcu_torture_writer(void *arg) 
			}

		}

		rcutorture_record_progress(++rcu_torture_current_version);

		rcu_torture_writer_state = RTWS_STUTTER;

		stutter_wait("rcu_torture_writer");

	} while (!torture_must_stop());

	rcu_torture_writer_state = RTWS_STOPPING;

	torture_kthread_stopping("rcu_torture_writer");

	return 0;

}
@@ -937,6 +959,7 @@ rcu_torture_printk(char *page) 
	int i;

	long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };

	long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };

	static unsigned long rtcv_snap = ULONG_MAX;



	for_each_possible_cpu(cpu) {

		for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
@@ -997,6 +1020,20 @@ rcu_torture_printk(char *page) 
	page += sprintf(page, "\n");

	if (cur_ops->stats)

		cur_ops->stats(page);

	if (rtcv_snap == rcu_torture_current_version &&

	    rcu_torture_current != NULL) {

		int __maybe_unused flags;

		unsigned long __maybe_unused gpnum;

		unsigned long __maybe_unused completed;



		rcutorture_get_gp_data(cur_ops->ttype,

				       &flags, &gpnum, &completed);

		page += sprintf(page,

				"??? Writer stall state %d g%lu c%lu f%#x\n",

				rcu_torture_writer_state,

				gpnum, completed, flags);

	}

	rtcv_snap = rcu_torture_current_version;

}



/*

kernel/rcu/tree.c

+33 −0
Original line number Diff line number Diff line
@@ -293,6 +293,39 @@ void rcutorture_record_test_transition(void) 
}

EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);



/*

 * Send along grace-period-related data for rcutorture diagnostics.

 */

void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,

			    unsigned long *gpnum, unsigned long *completed)

{

	struct rcu_state *rsp = NULL;



	switch (test_type) {

	case RCU_FLAVOR:

		rsp = rcu_state;

		break;

	case RCU_BH_FLAVOR:

		rsp = &rcu_bh_state;

		break;

	case RCU_SCHED_FLAVOR:

		rsp = &rcu_sched_state;

		break;

	default:

		break;

	}

	if (rsp != NULL) {

		*flags = ACCESS_ONCE(rsp->gp_flags);

		*gpnum = ACCESS_ONCE(rsp->gpnum);

		*completed = ACCESS_ONCE(rsp->completed);

		return;

	}

	*flags = 0;

	*gpnum = 0;

	*completed = 0;

}

EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);



/*

 * Record the number of writer passes through the current rcutorture test.

 * This is also used to correlate debugfs tracing stats with the rcutorture