- Pass a ucontext_t to _set_curthread. If non-NULL the new thread is set

as curthread in the new context, so that it will be set automatically when
  the thread is switched to.  This fixes a race where we'd run for a little
  while with curthread unset in _thread_start.

Reviewed by:	jeff

lib/libthr/arch/i386/i386/_setcurthread.c

@@ -27,6 +27,7 @@
  */
 
 #include <sys/types.h>
+#include <sys/ucontext.h>
 
 #include <stdio.h>
 
@@ -66,7 +67,7 @@ _retire_thread(void *entry)
 }
 
 void *
-_set_curthread(void *thr)
+_set_curthread(ucontext_t *uc, void *thr)
 {
 	union descriptor desc;
 	void **ldt_entry;
@@ -116,7 +117,10 @@ _set_curthread(void *thr)
 	/*
 	 * Set up our gs with the index into the ldt for this entry.
 	 */
-	_set_gs(LSEL(ldt_index, SEL_UPL));
+	if (uc != NULL)
+		uc->uc_mcontext.mc_gs = LSEL(ldt_index, SEL_UPL);
+	else
+		_set_gs(LSEL(ldt_index, SEL_UPL));
 
 	return (ldt_entry);
 }

lib/libthr/arch/sparc64/sparc64/_setcurthread.c

@@ -48,9 +48,12 @@ _retire_thread(void *v)
 }
 
 void *
-_set_curthread(struct pthread *thread)
+_set_curthread(ucontext_t *uc, struct pthread *thread)
 {
 
-	_curthread = thread;
+	if (uc != NULL)
+		uc->uc_mcontext.mc_global[6] = (uint64_t)thread;
+	else
+		_curthread = thread;
 	return (NULL);
 }

lib/libthr/thread/thr_create.c

@@ -116,7 +116,8 @@ _pthread_create(pthread_t * thread, const pthread_attr_t * attr,
 	getcontext(&new_thread->ctx);
 	new_thread->ctx.uc_stack.ss_sp = new_thread->stack;
 	new_thread->ctx.uc_stack.ss_size = pattr->stacksize_attr;
-	makecontext(&new_thread->ctx, _thread_start, 1, new_thread);
+	makecontext(&new_thread->ctx, _thread_start, 0);
+	new_thread->arch_id = _set_curthread(&new_thread->ctx, new_thread);
 
 	/* Copy the thread attributes: */
 	memcpy(&new_thread->attr, pattr, sizeof(struct pthread_attr));
@@ -208,12 +209,11 @@ _pthread_create(pthread_t * thread, const pthread_attr_t * attr,
 }
 
 void
-_thread_start(pthread_t thread)
+_thread_start(void)
 {
-	thread->arch_id = _set_curthread(thread);
 
 	/* Run the current thread's start routine with argument: */
-	pthread_exit(thread->start_routine(thread->arg));
+	pthread_exit(curthread->start_routine(curthread->arg));
 
 	/* This point should never be reached. */
 	PANIC("Thread has resumed after exit");

lib/libthr/thread/thr_init.c

@@ -219,7 +219,7 @@ _thread_init(void)
 		PANIC("Cannot allocate memory for initial thread");
 	}
 	_thread_initial = pthread;
-	pthread->arch_id = _set_curthread(pthread);
+	pthread->arch_id = _set_curthread(NULL, pthread);
 
 	/* Zero the initial thread structure: */
 	memset(pthread, 0, sizeof(struct pthread));

lib/libthr/thread/thr_private.h

@@ -686,7 +686,7 @@ char    *ttyname_r(int, char *, size_t);
 void	_cond_wait_backout(pthread_t);
 int     _find_thread(pthread_t);
 pthread_t _get_curthread(void);
-void	*_set_curthread(struct pthread *);
+void	*_set_curthread(ucontext_t *, struct pthread *);
 void	_retire_thread(void *arch_id);
 void	*_thread_stack_alloc(size_t, size_t);
 void	_thread_stack_free(void *, size_t, size_t);
@@ -720,7 +720,7 @@ void    _thread_dump_info(void);
 void    _thread_init(void);
 void	_thread_sig_wrapper(int sig, siginfo_t *info, ucontext_t *context);
 void	_thread_printf(int fd, const char *, ...);
-void    _thread_start(pthread_t);
+void    _thread_start(void);
 void	_thread_seterrno(pthread_t, int);
 pthread_addr_t _thread_gc(pthread_addr_t);
 void	_thread_enter_cancellation_point(void);