[cadcdev-svn-commits] [SCM] branch master updated. v2.0.0-1078-g0b93371

[ljsebald <ljs...@us...>]

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- Log -----------------------------------------------------------------
commit 0b93371d65163e8fb9e5a1902d5ec45be3e0df0f
Author: Falco Girgis <gyr...@gm...>
Date:   Sat Sep 23 23:10:02 2023 -0500

    Extended once_test to repro/verify deadlock issue (#312)
    
    - C++11's "std::async()" exposed an issue with the current
      implementation of kthread_once: it deadlocks when two separate threads
    attempt to use kthread_once on separate functions concurrently
    - I've extended the "once_test" to reproduce the issue with the kernel-level C API
    - The updated test simply spawns and joins another thread from within a
      "kthread_once" call, which also makes a "kthread_once" call

-----------------------------------------------------------------------

Summary of changes:
 .../dreamcast/basic/threading/once/once_test.c     | 61 ++++++++++++++++++----
 1 file changed, 50 insertions(+), 11 deletions(-)

diff --git a/examples/dreamcast/basic/threading/once/once_test.c b/examples/dreamcast/basic/threading/once/once_test.c
index 3029894..451e550 100644
--- a/examples/dreamcast/basic/threading/once/once_test.c
+++ b/examples/dreamcast/basic/threading/once/once_test.c
@@ -11,6 +11,9 @@
    the function. */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
 #include <kos/thread.h>
 #include <kos/once.h>
 
@@ -22,18 +25,38 @@
 #define UNUSED __attribute__((unused))
 #define THD_COUNT 600
 
-kthread_once_t once = KTHREAD_ONCE_INIT;
-spinlock_t lock = SPINLOCK_INITIALIZER;
-int counter = 0;
+static kthread_once_t once = KTHREAD_ONCE_INIT;
+static spinlock_t lock = SPINLOCK_INITIALIZER;
+static int counter = 0;
 
-void once_func(void) {
+static void inner_once_func(void) {
     spinlock_lock(&lock);
     ++counter;
     spinlock_unlock(&lock);
 }
 
-void *thd_func(void *param UNUSED) {
-    kthread_t *cur = thd_get_current();
+static void *inner_thd_func(void *param UNUSED) {
+    static kthread_once_t inner_once = KTHREAD_ONCE_INIT;
+    const kthread_t *cur = thd_get_current();
+
+    printf("Thd %d: Attempting to call inner kthread_once\n", cur->tid);
+    kthread_once(&inner_once, &inner_once_func);    
+    printf("Thd %d: inner kthread_once returned\n", cur->tid);
+    
+    return NULL;
+}
+
+static void once_func(void) {
+    const kthread_t *cur = thd_get_current();
+
+    printf("Thd %d: Spawning subthread\n", cur->tid);
+    kthread_t *subthd = thd_create(0, &inner_thd_func, NULL);
+    thd_join(subthd, NULL);
+    printf("Thd %d: Joined subthread\n", cur->tid);
+}
+
+static void *thd_func(void *param UNUSED) {
+    const kthread_t *cur = thd_get_current();
 
     printf("Thd %d: Attempting to call kthread_once\n", cur->tid);
     kthread_once(&once, &once_func);
@@ -44,7 +67,7 @@ void *thd_func(void *param UNUSED) {
 KOS_INIT_FLAGS(INIT_DEFAULT);
 
 int main(int argc, char *argv[]) {
-    int i;
+    int i, retval, success = 1;
     kthread_t *thds[THD_COUNT];
 
     cont_btn_callback(0, CONT_START | CONT_A | CONT_B | CONT_X | CONT_Y,
@@ -57,16 +80,32 @@ int main(int argc, char *argv[]) {
 
     for(i = 0; i < THD_COUNT; ++i) {
         thds[i] = thd_create(0, &thd_func, NULL);
+        
+        if(!thds[i]) {
+            fprintf(stderr, "Failed to spawn thread[%d]: %s\n",
+                    i, strerror(errno));
+            success = 0;
+        }
     }
 
     printf("Waiting for the threads to finish\n");
 
     for(i = 0; i < THD_COUNT; ++i) {
-        thd_join(thds[i], NULL);
+        if((retval = thd_join(thds[i], NULL) < 0)) {
+            fprintf(stderr, "Failed to join thread[%d]: %d\n", 
+                    i, retval);
+            success = 0;
+        }
     }
 
-    printf("Final counter value: %d (expected 1)\n", counter);
-    printf("Test finished\n");
+    printf("Final counter value: %d (expected 1)\n\n", counter);
 
-    return 0;
+    if(success && counter == 1) {
+        printf("***** ONCE_TEST PASSED *****\n");
+        return EXIT_SUCCESS;
+    }
+    else {
+        fprintf(stderr, "***** ONCE_TEST FAILED *****\n");
+        return EXIT_FAILURE;
+    }
 }


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