add support for thread scheduling (POSIX TPS option)

linux's sched_* syscalls actually implement the TPS (thread
scheduling) functionality, not the PS (process scheduling)
functionality which the sched_* functions are supposed to have.
omitting support for the PS option (and having the sched_* interfaces
fail with ENOSYS rather than omitting them, since some broken software
assumes they exist) seems to be the only conforming way to do this on
linux.

include/pthread.h

@@ -91,6 +91,10 @@ int pthread_setcanceltype(int, int *);
 void pthread_testcancel(void);
 int pthread_cancel(pthread_t);
 
+int pthread_getschedparam(pthread_t, int *__restrict, struct sched_param *__restrict);
+int pthread_setschedparam(pthread_t, int, const struct sched_param *);
+int pthread_setschedprio(pthread_t, int);
+
 int pthread_once(pthread_once_t *, void (*)(void));
 
 int pthread_mutex_init(pthread_mutex_t *__restrict, const pthread_mutexattr_t *__restrict);

include/sched.h

@@ -32,6 +32,9 @@ int     sched_yield(void);
 #define SCHED_OTHER 0
 #define SCHED_FIFO 1
 #define SCHED_RR 2
+#define SCHED_BATCH 3
+#define SCHED_IDLE 5
+#define SCHED_RESET_ON_FORK 0x40000000
 
 #ifdef _GNU_SOURCE
 #define CSIGNAL		0x000000ff

include/spawn.h

@@ -55,6 +55,11 @@ int posix_spawnattr_getsigmask(const posix_spawnattr_t *__restrict, sigset_t *__
 int posix_spawnattr_setsigdefault(posix_spawnattr_t *__restrict, const sigset_t *__restrict);
 int posix_spawnattr_getsigdefault(const posix_spawnattr_t *__restrict, sigset_t *__restrict);
 
+int posix_spawnattr_setschedparam(posix_spawnattr_t *__restrict, const struct sched_param *__restrict);
+int posix_spawnattr_getschedparam(const posix_spawnattr_t *__restrict, struct sched_param *__restrict);
+int posix_spawnattr_setschedpolicy(posix_spawnattr_t *__restrict, int);
+int posix_spawnattr_getschedpolicy(const posix_spawnattr_t *__restrict, int *);
+
 int posix_spawn_file_actions_init(posix_spawn_file_actions_t *);
 int posix_spawn_file_actions_destroy(posix_spawn_file_actions_t *);
 

src/internal/pthread_impl.h

@@ -40,6 +40,8 @@ struct pthread {
 	locale_t locale;
 	int killlock[2];
 	int exitlock[2];
+	int startlock[2];
+	unsigned long sigmask[__SYSCALL_SSLEN/sizeof(long)];
 };
 
 struct __timer {
@@ -53,6 +55,9 @@ struct __timer {
 #define _a_guardsize __u.__s[1]
 #define _a_stackaddr __u.__s[2]
 #define _a_detach __u.__i[3*__SU+0]
+#define _a_sched __u.__i[3*__SU+1]
+#define _a_policy __u.__i[3*__SU+2]
+#define _a_prio __u.__i[3*__SU+3]
 #define _m_type __u.__i[0]
 #define _m_lock __u.__i[1]
 #define _m_waiters __u.__i[2]

src/process/posix_spawnattr_sched.c

+#include <spawn.h>
+#include <sched.h>
+#include <errno.h>
+
+int posix_spawnattr_getschedparam(const posix_spawnattr_t *restrict attr,
+	struct sched_param *restrict schedparam)
+{
+	return ENOSYS;
+}
+
+int posix_spawnattr_setschedparam(posix_spawnattr_t *restrict attr,
+	const struct sched_param *restrict schedparam)
+{
+	return ENOSYS;
+}
+
+int posix_spawnattr_getschedpolicy(const posix_spawnattr_t *restrict attr, int *policy)
+{
+	return ENOSYS;
+}
+
+int posix_spawnattr_setschedpolicy(posix_spawnattr_t *restrict attr, int policy)
+{
+	return ENOSYS;
+}

src/sched/sched_get_priority_max.c

 #include <sched.h>
+#include "syscall.h"
 
 int sched_get_priority_max(int policy)
 {
-	return 0;
+	return syscall(SYS_sched_get_priority_max, policy);
 }
 
 int sched_get_priority_min(int policy)
 {
-	return 0;
+	return syscall(SYS_sched_get_priority_min, policy);
 }

src/sched/sched_getparam.c

 #include <sched.h>
+#include <errno.h>
 #include "syscall.h"
 
 int sched_getparam(pid_t pid, struct sched_param *param)
 {
-	return syscall(SYS_sched_getparam, pid, param);
+	return __syscall_ret(-ENOSYS);
 }

src/sched/sched_getscheduler.c

 #include <sched.h>
+#include <errno.h>
 #include "syscall.h"
 
 int sched_getscheduler(pid_t pid)
 {
-	return syscall(SYS_sched_getscheduler, pid);
+	return __syscall_ret(-ENOSYS);
 }

src/sched/sched_rr_get_interval.c

@@ -5,4 +5,3 @@ int sched_rr_get_interval(pid_t pid, struct timespec *ts)
 {
 	return syscall(SYS_sched_rr_get_interval, pid, ts);
 }
-

src/sched/sched_setparam.c

 #include <sched.h>
+#include <errno.h>
 #include "syscall.h"
 
 int sched_setparam(pid_t pid, const struct sched_param *param)
 {
-	static const struct sched_param def;
-	return syscall(SYS_sched_setparam, pid, &def);
+	return __syscall_ret(-ENOSYS);
 }

src/sched/sched_setscheduler.c

 #include <sched.h>
+#include <errno.h>
 #include "syscall.h"
 
 int sched_setscheduler(pid_t pid, int sched, const struct sched_param *param)
 {
-	static const struct sched_param def;
-	return syscall(SYS_sched_setscheduler, pid, 0, &def);
+	return __syscall_ret(-ENOSYS);
 }

src/thread/pthread_attr_getinheritsched.c

+#include "pthread_impl.h"
+
+int pthread_attr_getinheritsched(const pthread_attr_t *a, int *inherit)
+{
+	*inherit = a->_a_sched;
+	return 0;
+}

src/thread/pthread_attr_getschedparam.c

@@ -2,6 +2,6 @@
 
 int pthread_attr_getschedparam(const pthread_attr_t *restrict a, struct sched_param *restrict param)
 {
-	param->sched_priority = 0;
+	param->sched_priority = a->_a_prio;
 	return 0;
 }

src/thread/pthread_attr_getschedpolicy.c

+#include "pthread_impl.h"
+
+int pthread_attr_getschedpolicy(const pthread_attr_t *a, int *policy)
+{
+	*policy = a->_a_policy;
+	return 0;
+}

src/thread/pthread_attr_getscope.c

@@ -2,5 +2,6 @@
 
 int pthread_attr_getscope(const pthread_attr_t *restrict a, int *restrict scope)
 {
+	*scope = PTHREAD_SCOPE_SYSTEM;
 	return 0;
 }

src/thread/pthread_attr_setinheritsched.c

+#include "pthread_impl.h"
+
+int pthread_attr_setinheritsched(pthread_attr_t *a, int inherit)
+{
+	if (inherit > 1U) return EINVAL;
+	a->_a_sched = inherit;
+	return 0;
+}

src/thread/pthread_attr_setschedparam.c

@@ -2,6 +2,6 @@
 
 int pthread_attr_setschedparam(pthread_attr_t *restrict a, const struct sched_param *restrict param)
 {
-	if (param->sched_priority) return ENOTSUP;
+	a->_a_prio = param->sched_priority;
 	return 0;
 }

src/thread/pthread_attr_setschedpolicy.c

+#include "pthread_impl.h"
+
+int pthread_attr_setschedpolicy(pthread_attr_t *a, int policy)
+{
+	a->_a_policy = policy;
+	return 0;
+}

src/thread/pthread_attr_setscope.c

@@ -2,6 +2,12 @@
 
 int pthread_attr_setscope(pthread_attr_t *a, int scope)
 {
-	if (scope > 1U) return EINVAL;
-	return 0;
+	switch (scope) {
+	case PTHREAD_SCOPE_SYSTEM:
+		return 0;
+	case PTHREAD_SCOPE_PROCESS:
+		return ENOTSUP;
+	default:
+		return EINVAL;
+	}
 }

src/thread/pthread_create.c

@@ -62,6 +62,15 @@ void __do_cleanup_pop(struct __ptcb *cb)
 static int start(void *p)
 {
 	pthread_t self = p;
+	if (self->startlock[0]) {
+		__wait(self->startlock, 0, 1, 1);
+		if (self->startlock[0]) {
+			self->detached = 2;
+			pthread_exit(0);
+		}
+		__syscall(SYS_rt_sigprocmask, SIG_SETMASK,
+			self->sigmask, 0, __SYSCALL_SSLEN);
+	}
 	if (self->unblock_cancel)
 		__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
 			SIGPT_SET, 0, __SYSCALL_SSLEN);
@@ -95,6 +104,7 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 	struct pthread *self = pthread_self(), *new;
 	unsigned char *map, *stack, *tsd;
 	unsigned flags = 0x7d8f00;
+	int do_sched = 0;
 
 	if (!self) return ENOSYS;
 	if (!libc.threaded) {
@@ -144,6 +154,11 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 		new->detached = 1;
 		flags -= 0x200000;
 	}
+	if (attr && attr->_a_sched) {
+		do_sched = new->startlock[0] = 1;
+		__syscall(SYS_rt_sigprocmask, SIG_BLOCK,
+			SIGALL_SET, self->sigmask, __SYSCALL_SSLEN);
+	}
 	new->unblock_cancel = self->cancel;
 	new->canary = self->canary;
 
@@ -152,11 +167,25 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
 
 	__release_ptc();
 
+	if (do_sched) {
+		__syscall(SYS_rt_sigprocmask, SIG_SETMASK,
+			new->sigmask, 0, __SYSCALL_SSLEN);
+	}
+
 	if (ret < 0) {
 		a_dec(&libc.threads_minus_1);
 		munmap(map, size);
 		return EAGAIN;
 	}
+
+	if (do_sched) {
+		ret = __syscall(SYS_sched_setscheduler, new->tid,
+			attr->_a_policy, &attr->_a_prio);
+		a_store(new->startlock, ret<0 ? 2 : 0);
+		__wake(new->startlock, 1, 1);
+		if (ret < 0) return -ret;
+	}
+
 	*res = new;
 	return 0;
 }

src/thread/pthread_getschedparam.c

+#include "pthread_impl.h"
+
+int pthread_getschedparam(pthread_t t, int *restrict policy, struct sched_param *restrict param)
+{
+	int r;
+	__lock(t->killlock);
+	if (t->dead) {
+		r = ESRCH;
+	} else {
+		r = -__syscall(SYS_sched_getparam, t->tid, &param);
+		if (!r) {
+			*policy = __syscall(SYS_sched_getscheduler, t->tid);
+		}
+	}
+	__unlock(t->killlock);
+	return r;
+}

src/thread/pthread_setschedparam.c

+#include "pthread_impl.h"
+
+int pthread_setschedparam(pthread_t t, int policy, const struct sched_param *param)
+{
+	int r;
+	__lock(t->killlock);
+	r = t->dead ? ESRCH : -__syscall(SYS_sched_setscheduler, t->tid, policy, &param);
+	__unlock(t->killlock);
+	return r;
+}

src/thread/pthread_setschedprio.c

+#include "pthread_impl.h"
+
+int pthread_setschedprio(pthread_t t, int prio)
+{
+	int r;
+	__lock(t->killlock);
+	r = t->dead ? ESRCH : -__syscall(SYS_sched_setparam, t->tid, &prio);
+	__unlock(t->killlock);
+	return r;
+}