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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: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-10-01 17:40:54 -07:00
parent 61670adcb4
commit e0aff97355
3 changed files with 50 additions and 3 deletions
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2
kernel/rcu/rcu.h
View File

@ -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;

31
kernel/rcu/rcutorture.c
View File

@ -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");

20
kernel/rcu/tree.c
View File

@ -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