Add some <sched.h> tests.

I was intending to change our behavior to match POSIX, but reality convinced
me otherwise.

Also add missing argument names to the header file on the assumption they'll
be shown in Studio one day.

Bug: http://b/26203902
Test: ran tests
Change-Id: I2aaea48a88d408a32925033fc8f17448fb63252e

2 files changed, 43 insertions, 11 deletions

diff --git a/libc/include/sched.h b/libc/include/sched.h
index d4072024d..b8ef44b3d 100644
--- a/libc/include/sched.h
+++ b/libc/include/sched.h
@@ -25,6 +25,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef _SCHED_H_
 #define _SCHED_H_
 
@@ -41,22 +42,22 @@ struct sched_param {
   int sched_priority;
 };
 
-int sched_setscheduler(pid_t, int, const struct sched_param*);
-int sched_getscheduler(pid_t);
+int sched_setscheduler(pid_t pid, int policy, const struct sched_param* param);
+int sched_getscheduler(pid_t pid);
 int sched_yield(void);
-int sched_get_priority_max(int);
-int sched_get_priority_min(int);
-int sched_setparam(pid_t, const struct sched_param*);
-int sched_getparam(pid_t, struct sched_param*);
-int sched_rr_get_interval(pid_t, struct timespec*);
+int sched_get_priority_max(int policy);
+int sched_get_priority_min(int policy);
+int sched_setparam(pid_t pid, const struct sched_param* param);
+int sched_getparam(pid_t pid, struct sched_param* param);
+int sched_rr_get_interval(pid_t pid, struct timespec* quantum);
 
 #if defined(__USE_GNU)
 
-int clone(int (*)(void*), void*, int, void*, ...) __INTRODUCED_IN_ARM(9)
-    __INTRODUCED_IN_MIPS(12) __INTRODUCED_IN_X86(17);
-int unshare(int) __INTRODUCED_IN(17);
+int clone(int (*fn)(void*), void* child_stack, int flags, void* arg, ...)
+    __INTRODUCED_IN_ARM(9) __INTRODUCED_IN_MIPS(12) __INTRODUCED_IN_X86(17);
+int unshare(int flags) __INTRODUCED_IN(17);
 int sched_getcpu(void) __INTRODUCED_IN(12);
-int setns(int, int) __INTRODUCED_IN(21);
+int setns(int fd, int ns_type) __INTRODUCED_IN(21);
 
 #ifdef __LP64__
 #define CPU_SETSIZE 1024
diff --git a/tests/sched_test.cpp b/tests/sched_test.cpp
index a4cffc07f..e70528eef 100644
--- a/tests/sched_test.cpp
+++ b/tests/sched_test.cpp
@@ -270,3 +270,34 @@ TEST(sched, cpu_equal_s) {
   CPU_FREE(set1);
   CPU_FREE(set2);
 }
+
+TEST(sched, sched_get_priority_min_sched_get_priority_max) {
+  EXPECT_LE(sched_get_priority_min(SCHED_BATCH), sched_get_priority_max(SCHED_BATCH));
+  EXPECT_LE(sched_get_priority_min(SCHED_FIFO), sched_get_priority_max(SCHED_FIFO));
+  EXPECT_LE(sched_get_priority_min(SCHED_IDLE), sched_get_priority_max(SCHED_IDLE));
+  EXPECT_LE(sched_get_priority_min(SCHED_OTHER), sched_get_priority_max(SCHED_OTHER));
+  EXPECT_LE(sched_get_priority_min(SCHED_RR), sched_get_priority_max(SCHED_RR));
+}
+
+TEST(sched, sched_getscheduler_sched_setscheduler) {
+  // POSIX: "If pid is zero, the scheduling policy shall be returned for the
+  // calling process".
+  ASSERT_EQ(sched_getscheduler(getpid()), sched_getscheduler(0));
+
+  const int original_policy = sched_getscheduler(getpid());
+  sched_param p = {};
+  p.sched_priority = sched_get_priority_min(original_policy);
+  errno = 0;
+  ASSERT_EQ(-1, sched_setscheduler(getpid(), INT_MAX, &p));
+  ASSERT_EQ(EINVAL, errno);
+
+  ASSERT_EQ(0, sched_getparam(getpid(), &p));
+  ASSERT_EQ(original_policy, sched_setscheduler(getpid(), SCHED_BATCH, &p));
+  // POSIX says this should return the previous policy (here SCHED_BATCH),
+  // but the Linux system call doesn't, and the glibc wrapper doesn't correct
+  // this (the "returns 0" behavior is even documented on the man page in
+  // the BUGS section). This was our historical behavior too, so in the
+  // absence of reasons to break compatibility with ourselves and glibc, we
+  // don't behave as POSIX specifies. http://b/26203902.
+  ASSERT_EQ(0, sched_setscheduler(getpid(), original_policy, &p));
+}