Changeset 9a41e6e in mainline

Timestamp:

2025-03-05T22:54:36Z (4 days ago)

Author:

Matěj Volf <git@…>

Children:

7064e71

Parents:

2482192

Message:

implement pthread thread-local storage keys

File:

• uspace/lib/posix/src/pthread/keys.c (modified) (1 diff)

uspace/lib/posix/src/pthread/keys.c

@@ -36 +36 @@
 #include <pthread.h>
 #include <errno.h>
+#include <fibril.h>
+#include <stdatomic.h>
 #include "../internal/common.h"
+
+#define DPRINTF(format, ...) ((void) 0)
+
+static fibril_local bool fibril_initialized = false;
+static atomic_ushort next_key = 1; // skip the key 'zero'
+
+/*
+ * For now, we just support maximum of 100 keys. This can be improved
+ * in the future by implementing a dynamically growing array with
+ * reallocations, but that will require more synchronization.
+ */
+#define PTHREAD_KEYS_MAX 100
+static void (*destructors[PTHREAD_KEYS_MAX])(void *);
+
+static fibril_local void *key_data[PTHREAD_KEYS_MAX];
 
 void *pthread_getspecific(pthread_key_t key)
 {
-        not_implemented();
-        return NULL;
+        // initialization is done in setspecific -> if not initialized, nothing was set yet
+        if (!fibril_initialized) return NULL;
+
+        assert(key < PTHREAD_KEYS_MAX);
+        assert(key < next_key);
+        assert(key > 0);
+
+        return key_data[key];
+}
+
+static void pthread_key_on_fibril_exit(void) {
+        if (!fibril_initialized) return;
+
+        for (unsigned i = 0; i < PTHREAD_KEYS_MAX; i++) {
+                /*
+                 * Note that this doesn't cause a race with pthread_key_create:
+                 * if key `i` has not been assigned yet (it could be just being
+                 * created), key_data[i] has never been assigned, therefore it
+                 * is NULL, and the destructor is not checked at all.
+                 */
+                if (key_data[i] != NULL && destructors[i] != NULL)
+                                destructors[i](key_data[i]);
+        }
 }
 
 int pthread_setspecific(pthread_key_t key, const void *data)
 {
-        not_implemented();
-        return ENOTSUP;
+        if (!fibril_initialized) {
+                DPRINTF("initializing pthread keys\n");
+                errno_t res = fibril_add_exit_hook(pthread_key_on_fibril_exit);
+                if (res != EOK) return res;
+                for (unsigned i = 0; i < PTHREAD_KEYS_MAX; i++) {
+                        key_data[i] = NULL;
+                }
+                fibril_initialized = true;
+        }
+        assert(key < PTHREAD_KEYS_MAX);
+        assert(key < next_key);
+        assert(key > 0);
+
+        key_data[key] = (void *) data;
+        return EOK;
 }
 
 int pthread_key_delete(pthread_key_t key)
 {
-        not_implemented();
-        return ENOTSUP;
+        /*
+         * FIXME: this can cause a data race with another fibrill
+         * running on_fibril_exit. The obvious solution is to add
+         * a rwlock on the destructors array, which will be needed
+         * anyway if we want to support unlimited number of keys.
+         */
+        destructors[key] = NULL;
+        key_data[key] = NULL;
+
+        // TODO: the key could also be reused
+        return EOK;
 }
 
 int pthread_key_create(pthread_key_t *key, void (*destructor)(void *))
 {
-        not_implemented();
-        return ENOTSUP;
+        unsigned short k = atomic_fetch_add(&next_key, 1);
+        if (k >= PTHREAD_KEYS_MAX) {
+                atomic_store(&next_key, PTHREAD_KEYS_MAX + 1);
+                return ELIMIT;
+        }
+
+        destructors[k] = destructor;
+        *key = k;
+        return EOK;
 }