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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 00a7fd61b3c6540521109c4c79e412a0833bef02..82973738125b3abcbd304c73fdf09655706beda2 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -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)
 {
 }

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index bd30bc61bc05c273159541f260d047fa4747bc82..0d739e3797e3e6a5e4aeaa71d618d23714549fa8 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -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;
 }
 
 /*

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 0c47e300210ad61c3d79854426150fd5246f5750..3d15b5a82ae818bb7d105ad020f789262d0f5009 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -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