rcu tests: fix compilation on 32-bit ppc

32-bit PPC cannot do atomic operations on long long.  Inside the loops,
we are already using local counters that are summed at the end of
the run---with some exceptions (rcu_stress_count for rcutorture,
n_nodes for test-rcu-list): fix them to use the same technique.
For test-rcu-list, remove the mostly unused member "val" from the
list.  Then, use a mutex to protect the global counts.

Performance does not matter there because every thread will only enter
the critical section once.

Remaining uses of atomic instructions are for ints or pointers.

Reported-by: Andreas Faerber <afaerber@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 28 insertions, 22 deletions

diff --git a/tests/test-rcu-list.c b/tests/test-rcu-list.c
index 46b5e263e5..4c5f62e996 100644
--- a/tests/test-rcu-list.c
+++ b/tests/test-rcu-list.c
@@ -35,16 +35,15 @@
  * Test variables.
  */
 
-long long n_reads = 0LL;
-long long n_updates = 0LL;
-long long n_reclaims = 0LL;
-long long n_nodes_removed = 0LL;
-long long n_nodes = 0LL;
-int g_test_in_charge = 0;
+static QemuMutex counts_mutex;
+static long long n_reads = 0LL;
+static long long n_updates = 0LL;
+static long long n_reclaims = 0LL;
+static long long n_nodes_removed = 0LL;
+static long long n_nodes = 0LL;
+static int g_test_in_charge = 0;
 
-int nthreadsrunning;
-
-char argsbuf[64];
+static int nthreadsrunning;
 
 #define GOFLAG_INIT 0
 #define GOFLAG_RUN  1
@@ -92,21 +91,21 @@ static void wait_all_threads(void)
 struct list_element {
     QLIST_ENTRY(list_element) entry;
     struct rcu_head rcu;
-    long long val;
 };
 
 static void reclaim_list_el(struct rcu_head *prcu)
 {
     struct list_element *el = container_of(prcu, struct list_element, rcu);
     g_free(el);
-    atomic_add(&n_reclaims, 1);
+    /* Accessed only from call_rcu thread.  */
+    n_reclaims++;
 }
 
 static QLIST_HEAD(q_list_head, list_element) Q_list_head;
 
 static void *rcu_q_reader(void *arg)
 {
-    long long j, n_reads_local = 0;
+    long long n_reads_local = 0;
     struct list_element *el;
 
     *(struct rcu_reader_data **)arg = &rcu_reader;
@@ -118,8 +117,6 @@ static void *rcu_q_reader(void *arg)
     while (goflag == GOFLAG_RUN) {
         rcu_read_lock();
         QLIST_FOREACH_RCU(el, &Q_list_head, entry) {
-            j = atomic_read(&el->val);
-            (void)j;
             n_reads_local++;
             if (goflag == GOFLAG_STOP) {
                 break;
@@ -129,7 +126,9 @@ static void *rcu_q_reader(void *arg)
 
         g_usleep(100);
     }
-    atomic_add(&n_reads, n_reads_local);
+    qemu_mutex_lock(&counts_mutex);
+    n_reads += n_reads_local;
+    qemu_mutex_unlock(&counts_mutex);
     return NULL;
 }
 
@@ -137,6 +136,7 @@ static void *rcu_q_reader(void *arg)
 static void *rcu_q_updater(void *arg)
 {
     int j, target_el;
+    long long n_nodes_local = 0;
     long long n_updates_local = 0;
     long long n_removed_local = 0;
     struct list_element *el, *prev_el;
@@ -170,8 +170,7 @@ static void *rcu_q_updater(void *arg)
             j++;
             if (target_el == j) {
                 prev_el = g_new(struct list_element, 1);
-                atomic_add(&n_nodes, 1);
-                prev_el->val = atomic_read(&n_nodes);
+                n_nodes += n_nodes_local;
                 QLIST_INSERT_BEFORE_RCU(el, prev_el, entry);
                 break;
             }
@@ -181,8 +180,11 @@ static void *rcu_q_updater(void *arg)
         synchronize_rcu();
     }
     synchronize_rcu();
-    atomic_add(&n_updates, n_updates_local);
-    atomic_add(&n_nodes_removed, n_removed_local);
+    qemu_mutex_lock(&counts_mutex);
+    n_nodes += n_nodes_local;
+    n_updates += n_updates_local;
+    n_nodes_removed += n_removed_local;
+    qemu_mutex_unlock(&counts_mutex);
     return NULL;
 }
 
@@ -194,10 +196,11 @@ static void rcu_qtest_init(void)
     srand(time(0));
     for (i = 0; i < RCU_Q_LEN; i++) {
         new_el = g_new(struct list_element, 1);
-        new_el->val = i;
         QLIST_INSERT_HEAD_RCU(&Q_list_head, new_el, entry);
     }
-    atomic_add(&n_nodes, RCU_Q_LEN);
+    qemu_mutex_lock(&counts_mutex);
+    n_nodes += RCU_Q_LEN;
+    qemu_mutex_unlock(&counts_mutex);
 }
 
 static void rcu_qtest_run(int duration, int nreaders)
@@ -233,7 +236,9 @@ static void rcu_qtest(const char *test, int duration, int nreaders)
         call_rcu1(&prev_el->rcu, reclaim_list_el);
         n_removed_local++;
     }
-    atomic_add(&n_nodes_removed, n_removed_local);
+    qemu_mutex_lock(&counts_mutex);
+    n_nodes_removed += n_removed_local;
+    qemu_mutex_unlock(&counts_mutex);
     synchronize_rcu();
     while (n_nodes_removed > n_reclaims) {
         g_usleep(100);
@@ -277,6 +282,7 @@ int main(int argc, char *argv[])
 {
     int duration = 0, readers = 0;
 
+    qemu_mutex_init(&counts_mutex);
     if (argc >= 2) {
         if (argv[1][0] == '-') {
             g_test_init(&argc, &argv, NULL);