unix,win: utility for setting priority for thread (#4075)

Add uv_thread_setpriority for setting priority for threads created by
uv_thread_create. Add uv_thread_getpriority for getting thread priority.

For Linux by default, if the scheduling policy is SCHED_OTHER and the
priority is 0, we need to set the nice value.

Fixes: https://github.com/libuv/libuv/issues/4051

.gitignore

@@ -7,6 +7,7 @@
 *.sdf
 *.suo
 .vs/
+.vscode/
 *.VC.db
 *.VC.opendb
 core

CMakeLists.txt

@@ -655,6 +655,7 @@ if(LIBUV_BUILD_TESTS)
        test/test-thread-affinity.c
        test/test-thread-equal.c
        test/test-thread.c
+       test/test-thread-priority.c
        test/test-threadpool-cancel.c
        test/test-threadpool.c
        test/test-timer-again.c

Makefile.am

@@ -286,6 +286,7 @@ test_run_tests_SOURCES = test/blackhole-server.c \
                          test/test-thread-equal.c \
                          test/test-thread.c \
                          test/test-thread-affinity.c \
+                         test/test-thread-priority.c \
                          test/test-threadpool-cancel.c \
                          test/test-threadpool.c \
                          test/test-timer-again.c \

docs/src/threading.rst

@@ -132,6 +132,21 @@ Threads
 .. c:function:: int uv_thread_join(uv_thread_t *tid)
 .. c:function:: int uv_thread_equal(const uv_thread_t* t1, const uv_thread_t* t2)
 
+.. c:function:: int uv_thread_setpriority(uv_thread_t tid, int priority)
+    If the function succeeds, the return value is 0.
+    If the function fails, the return value is less than zero.
+    Sets the scheduling priority of the thread specified by tid. It requires elevated
+    privilege to set specific priorities on some platforms.
+    The priority can be set to the following constants. UV_THREAD_PRIORITY_HIGHEST, 
+    UV_THREAD_PRIORITY_ABOVE_NORMAL, UV_THREAD_PRIORITY_NORMAL, 
+    UV_THREAD_PRIORITY_BELOW_NORMAL, UV_THREAD_PRIORITY_LOWEST.
+.. c:function:: int uv_thread_getpriority(uv_thread_t tid, int* priority)
+    If the function succeeds, the return value is 0.
+    If the function fails, the return value is less than zero.
+    Retrieves the scheduling priority of the thread specified by tid. The value in the
+    output parameter priority is platform dependent.
+    For Linux, when schedule policy is SCHED_OTHER (default), priority is 0.
+
 Thread-local storage
 ^^^^^^^^^^^^^^^^^^^^
 

include/uv.h

@@ -1284,6 +1284,17 @@ UV_EXTERN uv_pid_t uv_os_getppid(void);
 UV_EXTERN int uv_os_getpriority(uv_pid_t pid, int* priority);
 UV_EXTERN int uv_os_setpriority(uv_pid_t pid, int priority);
 
+enum {
+  UV_THREAD_PRIORITY_HIGHEST = 2,
+  UV_THREAD_PRIORITY_ABOVE_NORMAL = 1,
+  UV_THREAD_PRIORITY_NORMAL = 0,
+  UV_THREAD_PRIORITY_BELOW_NORMAL = -1,
+  UV_THREAD_PRIORITY_LOWEST = -2,
+};
+
+UV_EXTERN int uv_thread_getpriority(uv_thread_t tid, int* priority);
+UV_EXTERN int uv_thread_setpriority(uv_thread_t tid, int priority);
+
 UV_EXTERN unsigned int uv_available_parallelism(void);
 UV_EXTERN int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count);
 UV_EXTERN void uv_free_cpu_info(uv_cpu_info_t* cpu_infos, int count);

src/unix/core.c

@@ -90,6 +90,7 @@ extern char** environ;
 #if defined(__linux__)
 # include <sched.h>
 # include <sys/syscall.h>
+# define gettid() syscall(SYS_gettid)
 # define uv__accept4 accept4
 #endif
 
@@ -1557,6 +1558,130 @@ int uv_os_setpriority(uv_pid_t pid, int priority) {
   return 0;
 }
 
+/**
+ * If the function succeeds, the return value is 0.
+ * If the function fails, the return value is non-zero.
+ * for Linux, when schedule policy is SCHED_OTHER (default), priority is 0.
+ * So the output parameter priority is actually the nice value.
+*/
+int uv_thread_getpriority(uv_thread_t tid, int* priority) {
+  int r;
+  int policy;
+  struct sched_param param;
+#ifdef __linux__
+  pid_t pid = gettid();
+#endif
+
+  if (priority == NULL)
+    return UV_EINVAL;
+
+  r = pthread_getschedparam(tid, &policy, &param);
+  if (r != 0)
+    return UV__ERR(errno);
+
+#ifdef __linux__
+  if (SCHED_OTHER == policy && pthread_equal(tid, pthread_self())) {
+    errno = 0;
+    r = getpriority(PRIO_PROCESS, pid);
+    if (r == -1 && errno != 0)
+      return UV__ERR(errno);
+    *priority = r;
+    return 0;
+  }
+#endif
+
+  *priority = param.sched_priority;
+  return 0;
+}
+
+#ifdef __linux__
+static int set_nice_for_calling_thread(int priority) {
+  int r;
+  int nice;
+
+  if (priority < UV_THREAD_PRIORITY_LOWEST || priority > UV_THREAD_PRIORITY_HIGHEST)
+    return UV_EINVAL;
+
+  pid_t pid = gettid();
+  nice = 0 - priority * 2;
+  r = setpriority(PRIO_PROCESS, pid, nice);
+  if (r != 0)
+    return UV__ERR(errno);
+  return 0;
+}
+#endif
+
+/**
+ * If the function succeeds, the return value is 0.
+ * If the function fails, the return value is non-zero.
+*/
+int uv_thread_setpriority(uv_thread_t tid, int priority) {
+  int r;
+  int min;
+  int max;
+  int range;
+  int prio;
+  int policy;
+  struct sched_param param;
+
+  if (priority < UV_THREAD_PRIORITY_LOWEST || priority > UV_THREAD_PRIORITY_HIGHEST)
+    return UV_EINVAL;
+
+  r = pthread_getschedparam(tid, &policy, &param);
+  if (r != 0)
+    return UV__ERR(errno);
+
+#ifdef __linux__
+/**
+ * for Linux, when schedule policy is SCHED_OTHER (default), priority must be 0,
+ * we should set the nice value in this case.
+*/
+  if (SCHED_OTHER == policy && pthread_equal(tid, pthread_self()))
+    return set_nice_for_calling_thread(priority);
+#endif
+
+#ifdef __PASE__
+  min = 1;
+  max = 127;
+#else
+  min = sched_get_priority_min(policy);
+  max = sched_get_priority_max(policy);
+#endif
+
+  if (min == -1 || max == -1)
+    return UV__ERR(errno);
+
+  range = max - min;
+
+  switch (priority) {
+    case UV_THREAD_PRIORITY_HIGHEST:
+      prio = max;
+      break;
+    case UV_THREAD_PRIORITY_ABOVE_NORMAL:
+      prio = min + range * 3 / 4;
+      break;
+    case UV_THREAD_PRIORITY_NORMAL:
+      prio = min + range / 2;
+      break;
+    case UV_THREAD_PRIORITY_BELOW_NORMAL:
+      prio = min + range / 4;
+      break;
+    case UV_THREAD_PRIORITY_LOWEST:
+      prio = min;
+      break;
+    default:
+      return 0;
+  }
+
+  if (param.sched_priority != prio) {
+    param.sched_priority = prio;
+    r = pthread_setschedparam(tid, policy, &param);
+    if (r != 0)
+      return UV__ERR(errno);  
+  }
+
+  return 0;
+}
 
 int uv_os_uname(uv_utsname_t* buffer) {
   struct utsname buf;

src/win/util.c

@@ -1466,6 +1466,48 @@ int uv_os_setpriority(uv_pid_t pid, int priority) {
   return r;
 }
 
+int uv_thread_getpriority(uv_thread_t tid, int* priority) {
+  int r;
+
+  if (priority == NULL)
+    return UV_EINVAL;
+
+  r = GetThreadPriority(tid);
+  if (r == THREAD_PRIORITY_ERROR_RETURN)
+    return uv_translate_sys_error(GetLastError());
+
+  *priority = r;
+  return 0;
+}
+
+int uv_thread_setpriority(uv_thread_t tid, int priority) {
+  int r;
+
+  switch (priority) {
+    case UV_THREAD_PRIORITY_HIGHEST:
+      r = SetThreadPriority(tid, THREAD_PRIORITY_HIGHEST);
+      break;
+    case UV_THREAD_PRIORITY_ABOVE_NORMAL:
+      r = SetThreadPriority(tid, THREAD_PRIORITY_ABOVE_NORMAL);
+      break;
+    case UV_THREAD_PRIORITY_NORMAL:
+      r = SetThreadPriority(tid, THREAD_PRIORITY_NORMAL);
+      break;
+    case UV_THREAD_PRIORITY_BELOW_NORMAL:
+      r = SetThreadPriority(tid, THREAD_PRIORITY_BELOW_NORMAL);
+      break;
+    case UV_THREAD_PRIORITY_LOWEST:
+      r = SetThreadPriority(tid, THREAD_PRIORITY_LOWEST);
+      break;
+    default:
+      return 0;
+  }
+
+  if (r == 0)
+    return uv_translate_sys_error(GetLastError());
+
+  return 0;
+}
 
 int uv_os_uname(uv_utsname_t* buffer) {
   /* Implementation loosely based on

test/test-list.h

@@ -468,6 +468,7 @@ TEST_DECLARE   (thread_rwlock_trylock)
 TEST_DECLARE   (thread_create)
 TEST_DECLARE   (thread_equal)
 TEST_DECLARE   (thread_affinity)
+TEST_DECLARE   (thread_priority)
 TEST_DECLARE   (dlerror)
 #if (defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))) && \
     !defined(__sun)
@@ -1165,6 +1166,7 @@ TASK_LIST_START
   TEST_ENTRY  (thread_create)
   TEST_ENTRY  (thread_equal)
   TEST_ENTRY  (thread_affinity)
+  TEST_ENTRY  (thread_priority)
   TEST_ENTRY  (dlerror)
   TEST_ENTRY  (ip4_addr)
   TEST_ENTRY  (ip6_addr_link_local)

test/test-thread-priority.c

@@ -0,0 +1,105 @@
+/* Copyright libuv contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "task.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h> /* memset */
+
+#ifdef __POSIX__
+#include <pthread.h>
+#include <errno.h>
+#endif
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+
+uv_sem_t sem;
+
+static void simple_task(void *args) {
+  uv_sem_wait(&sem);
+  printf("in simple_task\n");
+}
+
+TEST_IMPL(thread_priority) {
+  int priority;
+#ifndef _WIN32
+  int min;
+  int max;
+  int policy;
+  struct sched_param param;
+#endif
+  uv_thread_t task_id;
+
+  /* Verify that passing a NULL pointer returns UV_EINVAL. */
+  ASSERT_EQ(UV_EINVAL, uv_thread_getpriority(0, NULL));
+  ASSERT_OK(uv_sem_init(&sem, 1));
+  uv_sem_wait(&sem);
+  ASSERT_OK(uv_thread_create(&task_id, simple_task, NULL));
+  ASSERT_OK(uv_thread_getpriority(task_id, &priority));
+
+#ifdef _WIN32
+  ASSERT_EQ(priority, THREAD_PRIORITY_NORMAL);
+#else
+  ASSERT_OK(pthread_getschedparam(task_id, &policy, &param));
+#ifdef __PASE__
+  min = 1;
+  max = 127;
+#else
+  min = sched_get_priority_min(policy);
+  max = sched_get_priority_max(policy);
+#endif
+  ASSERT(priority >= min && priority <= max);
+#endif
+
+  ASSERT_OK(uv_thread_setpriority(task_id, UV_THREAD_PRIORITY_LOWEST));
+  ASSERT_OK(uv_thread_getpriority(task_id, &priority));
+
+#ifdef _WIN32
+  ASSERT_EQ(priority, THREAD_PRIORITY_LOWEST);
+#else
+  ASSERT_EQ(priority, min);
+#endif
+
+/**
+ * test set nice value for the calling thread with default schedule policy
+*/
+#ifdef __linux__
+  ASSERT_OK(uv_thread_getpriority(pthread_self(), &priority));
+  ASSERT_EQ(priority, 0);
+  ASSERT_OK(uv_thread_setpriority(pthread_self(), UV_THREAD_PRIORITY_LOWEST));
+  ASSERT_OK(uv_thread_getpriority(pthread_self(), &priority));
+  ASSERT_EQ(priority, (0 - UV_THREAD_PRIORITY_LOWEST * 2));
+#endif
+
+  uv_sem_post(&sem);
+
+  ASSERT_OK(uv_thread_join(&task_id));
+
+  uv_sem_destroy(&sem);
+
+  return 0;
+}