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rcutorture: Add forward-progress checking for writer
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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: Paul E. McKenney <[email protected]>
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@paulmck
paulmck committed May 13, 2014
1 parent c9eaa44 commit ad0dc7f
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Showing 3 changed files with 89 additions and 0 deletions.
19 changes: 19 additions & 0 deletions include/linux/rcupdate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand All @@ -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)
{
}
Expand Down
37 changes: 37 additions & 0 deletions kernel/rcu/rcutorture.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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. */
Expand Down Expand Up @@ -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. */
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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. */
Expand Down Expand Up @@ -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;
Expand All @@ -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);
Expand All @@ -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;
}
Expand Down Expand Up @@ -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++) {
Expand Down Expand Up @@ -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;
}

/*
Expand Down
33 changes: 33 additions & 0 deletions kernel/rcu/tree.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down

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