Merge branch 'contrib/github_pr_15132' into 'master'

fix(newlib): usleep returning early (GitHub PR)

Closes IDFGH-14342

See merge request espressif/esp-idf!38483

Author: sudeep-mohanty

components/cxx/test_apps/general/main/CMakeLists.txt

@@ -1,2 +1,2 @@
 idf_component_register(SRCS "test_cxx_general.cpp"
-                       PRIV_REQUIRES unity driver)
+                       PRIV_REQUIRES unity driver esp_timer)

components/cxx/test_apps/general/main/test_cxx_general.cpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -14,6 +14,9 @@
 #include "unity.h"
 #include "unity_test_utils.h"
 #include "soc/soc.h"
+#include <chrono>
+#include <thread>
+#include "esp_timer.h"
 
 extern "C" void setUp()
 {
@@ -319,6 +322,29 @@ TEST_CASE("stack smashing protection CXX", "[stack_smash]")
     recur_and_smash_cxx();
 }
 
+TEST_CASE("test std::this_thread::sleep_for basic functionality", "[misc]")
+{
+    const int us_per_tick = portTICK_PERIOD_MS * 1000;
+
+    // Test sub-tick sleep
+    const auto short_sleep = std::chrono::microseconds(us_per_tick / 4);
+    int64_t start = esp_timer_get_time();
+    std::this_thread::sleep_for(short_sleep);
+    int64_t end = esp_timer_get_time();
+    int64_t elapsed_us = end - start;
+    printf("short sleep: %lld us\n", elapsed_us);
+    TEST_ASSERT_GREATER_OR_EQUAL(short_sleep.count(), elapsed_us);
+
+    // Test multi-tick sleep
+    const auto long_sleep = std::chrono::microseconds(us_per_tick * 2);
+    start = esp_timer_get_time();
+    std::this_thread::sleep_for(long_sleep);
+    end = esp_timer_get_time();
+    elapsed_us = end - start;
+    printf("long sleep: %lld us\n", elapsed_us);
+    TEST_ASSERT_GREATER_OR_EQUAL(long_sleep.count(), elapsed_us);
+}
+
 extern "C" void app_main(void)
 {
     s_testTLS.foo(); /* allocates memory that will be reused */

components/newlib/src/time.c

@@ -207,10 +207,25 @@ int usleep(useconds_t us)
     if (us < us_per_tick) {
         esp_rom_delay_us((uint32_t) us);
     } else {
-        /* since vTaskDelay(1) blocks for anywhere between 0 and portTICK_PERIOD_MS,
-         * round up to compensate.
-         */
-        vTaskDelay((us + us_per_tick - 1) / us_per_tick);
+        /* vTaskDelay may return up to (n-1) tick periods due to the tick ISR
+           being asynchronous to the call. We must sleep at least the specified
+           time, or longer. Checking the monotonic clock allows making an
+           additional call to vTaskDelay when needed to ensure minimal time is
+           actually slept. Adding `us_per_tick - 1` prevents ever passing 0 to
+           vTaskDelay().
+        */
+        uint64_t now_us = esp_time_impl_get_time();
+        uint64_t target_us = now_us + us;
+        do {
+            vTaskDelay((((target_us - now_us) + us_per_tick - 1) / us_per_tick));
+            now_us = esp_time_impl_get_time();
+            /* If the time left until the target is less than 1 tick, then we use ROM delay to fill the gap */
+            uint64_t time_left = target_us - now_us;
+            if (time_left != 0 && time_left < us_per_tick) {
+                esp_rom_delay_us(time_left);
+                break;
+            }
+        } while (now_us < target_us);
     }
     return 0;
 }

components/newlib/test_apps/newlib/main/test_time.c

@@ -1,11 +1,12 @@
 /*
- * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
+#include <unistd.h>
 #include "unity.h"
 #include <time.h>
 #include <sys/time.h>
@@ -77,6 +78,27 @@ TEST_CASE("Reading RTC registers on APP CPU doesn't affect clock", "[newlib]")
 
 #endif // (CONFIG_FREERTOS_NUMBER_OF_CORES == 2) && CONFIG_IDF_TARGET_ARCH_XTENSA
 
+TEST_CASE("test usleep basic functionality", "[newlib]")
+{
+    const int us_per_tick = portTICK_PERIOD_MS * 1000;
+
+    // Test sub-tick sleep such that usleep() uses ROM delay path
+    const int short_sleep_us = us_per_tick / 4;
+    int64_t start = esp_timer_get_time();
+    TEST_ASSERT_EQUAL(0, usleep(short_sleep_us));
+    int64_t end = esp_timer_get_time();
+    printf("short sleep: %lld us\n", end - start);
+    TEST_ASSERT_GREATER_OR_EQUAL(short_sleep_us, end - start);
+
+    // Test multi-tick sleep using vTaskDelay path
+    const int long_sleep_us = us_per_tick * 2;
+    start = esp_timer_get_time();
+    TEST_ASSERT_EQUAL(0, usleep(long_sleep_us));
+    end = esp_timer_get_time();
+    printf("long sleep: %lld us\n", end - start);
+    TEST_ASSERT_GREATER_OR_EQUAL(long_sleep_us, end - start);
+}
+
 TEST_CASE("test adjtime function", "[newlib]")
 {
     struct timeval tv_time;