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Commit e0aff973 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcutorture: Dump grace-period diagnostics upon forward-progress OOM 



This commit adds an OOM notifier during rcutorture forward-progress
testing.  If this notifier is invoked, it dumps out some grace-period
state to help debug the forward-progress problem.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 61670adc

kernel/rcu/rcu.h

+2 −0
Original line number Diff line number Diff line
@@ -526,12 +526,14 @@ srcu_batches_completed(struct srcu_struct *sp) { return 0; } 
static inline void rcu_force_quiescent_state(void) { }

static inline void show_rcu_gp_kthreads(void) { }

static inline int rcu_get_gp_kthreads_prio(void) { return 0; }

static inline void rcu_fwd_progress_check(unsigned long j) { }

#else /* #ifdef CONFIG_TINY_RCU */

unsigned long rcu_get_gp_seq(void);

unsigned long rcu_exp_batches_completed(void);

unsigned long srcu_batches_completed(struct srcu_struct *sp);

void show_rcu_gp_kthreads(void);

int rcu_get_gp_kthreads_prio(void);

void rcu_fwd_progress_check(unsigned long j);

void rcu_force_quiescent_state(void);

extern struct workqueue_struct *rcu_gp_wq;

extern struct workqueue_struct *rcu_par_gp_wq;

kernel/rcu/rcutorture.c

+28 −3
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ 
#include <linux/vmalloc.h>

#include <linux/sched/debug.h>

#include <linux/sched/sysctl.h>

#include <linux/oom.h>



#include "rcu.h"
@@ -1624,6 +1625,7 @@ static struct rcu_fwd_cb *rcu_fwd_cb_head; 
static struct rcu_fwd_cb **rcu_fwd_cb_tail = &rcu_fwd_cb_head;

static long n_launders_cb;

static unsigned long rcu_fwd_startat;

static bool rcu_fwd_emergency_stop;

#define MAX_FWD_CB_JIFFIES	(8 * HZ) /* Maximum CB test duration. */

#define MIN_FWD_CB_LAUNDERS	3	/* This many CB invocations to count. */

#define MIN_FWD_CBS_LAUNDERED	100	/* Number of counted CBs. */
@@ -1681,7 +1683,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) 
	dur = sd4 + torture_random(&trs) % (sd - sd4);

	WRITE_ONCE(rcu_fwd_startat, jiffies);

	stopat = rcu_fwd_startat + dur;

	while (time_before(jiffies, stopat) && !torture_must_stop()) {

	while (time_before(jiffies, stopat) &&

	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {

		idx = cur_ops->readlock();

		udelay(10);

		cur_ops->readunlock(idx);
@@ -1689,7 +1692,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) 
			cond_resched();

	}

	(*tested_tries)++;

	if (!time_before(jiffies, stopat) && !torture_must_stop()) {

	if (!time_before(jiffies, stopat) &&

	    !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {

		(*tested)++;

		cver = READ_ONCE(rcu_torture_current_version) - cver;

		gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
@@ -1739,7 +1743,8 @@ static void rcu_torture_fwd_prog_cr(void) 
		n_launders_hist[i] = 0;

	cver = READ_ONCE(rcu_torture_current_version);

	gps = cur_ops->get_gp_seq();

	while (time_before(jiffies, stopat) && !torture_must_stop()) {

	while (time_before(jiffies, stopat) &&

	       !READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {

		rfcp = READ_ONCE(rcu_fwd_cb_head);

		rfcpn = NULL;

		if (rfcp)
@@ -1796,6 +1801,23 @@ static void rcu_torture_fwd_prog_cr(void) 
	}

}





/*

 * OOM notifier, but this only prints diagnostic information for the

 * current forward-progress test.

 */

static int rcutorture_oom_notify(struct notifier_block *self,

				 unsigned long notused, void *nfreed)

{

	rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat) / 2));

	WRITE_ONCE(rcu_fwd_emergency_stop, true);

	return NOTIFY_OK;

}



static struct notifier_block rcutorture_oom_nb = {

	.notifier_call = rcutorture_oom_notify

};



/* Carry out grace-period forward-progress testing. */

static int rcu_torture_fwd_prog(void *args)

{
@@ -1808,8 +1830,11 @@ static int rcu_torture_fwd_prog(void *args) 
		set_user_nice(current, MAX_NICE);

	do {

		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);

		WRITE_ONCE(rcu_fwd_emergency_stop, false);

		register_oom_notifier(&rcutorture_oom_nb);

		rcu_torture_fwd_prog_nr(&tested, &tested_tries);

		rcu_torture_fwd_prog_cr();

		unregister_oom_notifier(&rcutorture_oom_nb);



		/* Avoid slow periods, better to test when busy. */

		stutter_wait("rcu_torture_fwd_prog");

kernel/rcu/tree.c

+20 −0
Original line number Diff line number Diff line
@@ -2657,6 +2657,26 @@ rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp, 
	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

}



/*

 * Do a forward-progress check for rcutorture.  This is normally invoked

 * due to an OOM event.  The argument "j" gives the time period during

 * which rcutorture would like progress to have been made.

 */

void rcu_fwd_progress_check(unsigned long j)

{

	struct rcu_data *rdp;



	if (rcu_gp_in_progress()) {

		show_rcu_gp_kthreads();

	} else {

		preempt_disable();

		rdp = this_cpu_ptr(&rcu_data);

		rcu_check_gp_start_stall(rdp->mynode, rdp, j);

		preempt_enable();

	}

}

EXPORT_SYMBOL_GPL(rcu_fwd_progress_check);



/*

 * This does the RCU core processing work for the specified rcu_data

 * structures.  This may be called only from the CPU to whom the rdp