Commit 3a6cb58f authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcutorture: Add grace period after CPU offline 



Beyond a certain point in the CPU-hotplug offline process, timers get
stranded on the outgoing CPU, and won't fire until that CPU comes back
online, which might well be never.  This commit therefore adds a hook
in torture_onoff_init() that is invoked from torture_offline(), which
rcutorture uses to occasionally wait for a grace period.  This should
result in failures for RCU implementations that rely on stranded timers
eventually firing in the absence of the CPU coming back online.

Reported-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 0d8a9ea9

include/linux/torture.h

+2 −1
Original line number Diff line number Diff line
@@ -50,11 +50,12 @@ 
	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! %s\n", torture_type, s); } while (0)



/* Definitions for online/offline exerciser. */

typedef void torture_ofl_func(void);

bool torture_offline(int cpu, long *n_onl_attempts, long *n_onl_successes,

		     unsigned long *sum_offl, int *min_onl, int *max_onl);

bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,

		    unsigned long *sum_onl, int *min_onl, int *max_onl);

int torture_onoff_init(long ooholdoff, long oointerval);

int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f);

void torture_onoff_stats(void);

bool torture_onoff_failures(void);

kernel/locking/locktorture.c

+1 −1
Original line number Diff line number Diff line
@@ -970,7 +970,7 @@ static int __init lock_torture_init(void) 
	/* Prepare torture context. */

	if (onoff_interval > 0) {

		firsterr = torture_onoff_init(onoff_holdoff * HZ,

					      onoff_interval * HZ);

					      onoff_interval * HZ, NULL);

		if (firsterr)

			goto unwind;

	}

kernel/rcu/rcutorture.c

+10 −1
Original line number Diff line number Diff line
@@ -2243,6 +2243,14 @@ static void rcu_test_debug_objects(void) 
#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */

}



static void rcutorture_sync(void)

{

	static unsigned long n;



	if (cur_ops->sync && !(++n & 0xfff))

		cur_ops->sync();

}



static int __init

rcu_torture_init(void)

{
@@ -2404,7 +2412,8 @@ rcu_torture_init(void) 
	firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);

	if (firsterr)

		goto unwind;

	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval);

	firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,

				      rcutorture_sync);

	if (firsterr)

		goto unwind;

	firsterr = rcu_torture_stall_init();

kernel/torture.c

+5 −1
Original line number Diff line number Diff line
@@ -75,6 +75,7 @@ static DEFINE_MUTEX(fullstop_mutex); 
static struct task_struct *onoff_task;

static long onoff_holdoff;

static long onoff_interval;

static torture_ofl_func *onoff_f;

static long n_offline_attempts;

static long n_offline_successes;

static unsigned long sum_offline;
@@ -118,6 +119,8 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes, 
			pr_alert("%s" TORTURE_FLAG

				 "torture_onoff task: offlined %d\n",

				 torture_type, cpu);

		if (onoff_f)

			onoff_f();

		(*n_offl_successes)++;

		delta = jiffies - starttime;

		*sum_offl += delta;
@@ -243,11 +246,12 @@ stop: 
/*

 * Initiate online-offline handling.

 */

int torture_onoff_init(long ooholdoff, long oointerval)

int torture_onoff_init(long ooholdoff, long oointerval, torture_ofl_func *f)

{

#ifdef CONFIG_HOTPLUG_CPU

	onoff_holdoff = ooholdoff;

	onoff_interval = oointerval;

	onoff_f = f;

	if (onoff_interval <= 0)

		return 0;

	return torture_create_kthread(torture_onoff, NULL, onoff_task);

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