NPTL: Refactor createthread.c

1 files changed, 73 insertions, 159 deletions

diff --git a/nptl/createthread.c b/nptl/createthread.c
index 49442d9..7b05d48 100644
--- a/nptl/createthread.c
+++ b/nptl/createthread.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2002-2014 Free Software Foundation, Inc.
+/* Low-level thread creation for NPTL.  Linux version.
+   Copyright (C) 2002-2014 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -28,91 +29,119 @@
 #include <arch-fork.h>
 
 
-#define CLONE_SIGNAL		(CLONE_SIGHAND | CLONE_THREAD)
-
-
 #ifndef ARCH_CLONE
 # define ARCH_CLONE __clone
 #endif
 
+/* See the comments in pthread_create.c for the requirements for these
+   two macros and the create_thread function.  */
+
+#define START_THREAD_DEFN \
+  static int __attribute__ ((noreturn)) start_thread (void *arg)
+#define START_THREAD_SELF arg
+
+/* pthread_create.c defines this using START_THREAD_DEFN
+   We need a forward declaration here so we can take its address.  */
+static int start_thread (void *arg) __attribute__ ((noreturn));
 
 static int
-do_clone (struct pthread *pd, const struct pthread_attr *attr,
-	  int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
-	  int stopped)
+create_thread (struct pthread *pd, const struct pthread_attr *attr,
+	       bool stopped_start, STACK_VARIABLES_PARMS, bool *thread_ran)
 {
-  TLS_DEFINE_INIT_TP (tp, pd);
+  /* Determine whether the newly created threads has to be started
+     stopped since we have to set the scheduling parameters or set the
+     affinity.  */
+  if (attr != NULL
+      && (__glibc_unlikely (attr->cpuset != NULL)
+	  || __glibc_unlikely ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)))
+    stopped_start = true;
 
-  if (__glibc_unlikely (stopped != 0))
+  pd->stopped_start = stopped_start;
+  if (__glibc_unlikely (stopped_start))
     /* We make sure the thread does not run far by forcing it to get a
        lock.  We lock it here too so that the new thread cannot continue
        until we tell it to.  */
     lll_lock (pd->lock, LLL_PRIVATE);
 
-  /* One more thread.  We cannot have the thread do this itself, since it
-     might exist but not have been scheduled yet by the time we've returned
-     and need to check the value to behave correctly.  We must do it before
-     creating the thread, in case it does get scheduled first and then
-     might mistakenly think it was the only thread.  In the failure case,
-     we momentarily store a false value; this doesn't matter because there
-     is no kosher thing a signal handler interrupting us right here can do
-     that cares whether the thread count is correct.  */
-  atomic_increment (&__nptl_nthreads);
+  /* We rely heavily on various flags the CLONE function understands:
 
-  int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
-		       pd, &pd->tid, tp, &pd->tid);
+     CLONE_VM, CLONE_FS, CLONE_FILES
+	These flags select semantics with shared address space and
+	file descriptors according to what POSIX requires.
 
-  if (__glibc_unlikely (rc == -1))
-    {
-      atomic_decrement (&__nptl_nthreads); /* Oops, we lied for a second.  */
+     CLONE_SIGHAND, CLONE_THREAD
+	This flag selects the POSIX signal semantics and various
+	other kinds of sharing (itimers, POSIX timers, etc.).
 
-      /* Perhaps a thread wants to change the IDs and if waiting
-	 for this stillborn thread.  */
-      if (__builtin_expect (atomic_exchange_acq (&pd->setxid_futex, 0)
-			    == -2, 0))
-	lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
+     CLONE_SETTLS
+	The sixth parameter to CLONE determines the TLS area for the
+	new thread.
 
-      /* Free the resources.  */
-	__deallocate_stack (pd);
+     CLONE_PARENT_SETTID
+	The kernels writes the thread ID of the newly created thread
+	into the location pointed to by the fifth parameters to CLONE.
 
-      /* We have to translate error codes.  */
-      return errno == ENOMEM ? EAGAIN : errno;
-    }
+	Note that it would be semantically equivalent to use
+	CLONE_CHILD_SETTID but it is be more expensive in the kernel.
+
+     CLONE_CHILD_CLEARTID
+	The kernels clears the thread ID of a thread that has called
+	sys_exit() in the location pointed to by the seventh parameter
+	to CLONE.
+
+     The termination signal is chosen to be zero which means no signal
+     is sent.  */
+  const int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SYSVSEM
+			   | CLONE_SIGHAND | CLONE_THREAD
+			   | CLONE_SETTLS | CLONE_PARENT_SETTID
+			   | CLONE_CHILD_CLEARTID
+			   | 0);
+
+  TLS_DEFINE_INIT_TP (tp, pd);
+
+  if (__glibc_unlikely (ARCH_CLONE (&start_thread, STACK_VARIABLES_ARGS,
+				    clone_flags, pd, &pd->tid, tp, &pd->tid)
+			== -1))
+    return errno;
+
+  /* It's started now, so if we fail below, we'll have to cancel it
+     and let it clean itself up.  */
+  *thread_ran = true;
 
   /* Now we have the possibility to set scheduling parameters etc.  */
-  if (__glibc_unlikely (stopped != 0))
+  if (attr != NULL)
     {
       INTERNAL_SYSCALL_DECL (err);
-      int res = 0;
+      int res;
 
       /* Set the affinity mask if necessary.  */
       if (attr->cpuset != NULL)
 	{
+	  assert (stopped_start);
+
 	  res = INTERNAL_SYSCALL (sched_setaffinity, err, 3, pd->tid,
 				  attr->cpusetsize, attr->cpuset);
 
 	  if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err)))
+	  err_out:
 	    {
-	      /* The operation failed.  We have to kill the thread.  First
-		 send it the cancellation signal.  */
+	      /* The operation failed.  We have to kill the thread.
+		 We let the normal cancellation mechanism do the work.  */
+
 	      INTERNAL_SYSCALL_DECL (err2);
-	    err_out:
 	      (void) INTERNAL_SYSCALL (tgkill, err2, 3,
 				       THREAD_GETMEM (THREAD_SELF, pid),
 				       pd->tid, SIGCANCEL);
 
-	      /* We do not free the stack here because the canceled thread
-		 itself will do this.  */
-
-	      return (INTERNAL_SYSCALL_ERROR_P (res, err)
-		      ? INTERNAL_SYSCALL_ERRNO (res, err)
-		      : 0);
+	      return INTERNAL_SYSCALL_ERRNO (res, err);
 	    }
 	}
 
       /* Set the scheduling parameters.  */
       if ((attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0)
 	{
+	  assert (stopped_start);
+
 	  res = INTERNAL_SYSCALL (sched_setscheduler, err, 3, pd->tid,
 				  pd->schedpolicy, &pd->schedparam);
 
@@ -121,120 +150,5 @@ do_clone (struct pthread *pd, const struct pthread_attr *attr,
 	}
     }
 
-  /* We now have for sure more than one thread.  The main thread might
-     not yet have the flag set.  No need to set the global variable
-     again if this is what we use.  */
-  THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
-
   return 0;
 }
-
-
-static int
-create_thread (struct pthread *pd, const struct pthread_attr *attr,
-	       STACK_VARIABLES_PARMS)
-{
-#if TLS_TCB_AT_TP
-  assert (pd->header.tcb != NULL);
-#endif
-
-  /* We rely heavily on various flags the CLONE function understands:
-
-     CLONE_VM, CLONE_FS, CLONE_FILES
-	These flags select semantics with shared address space and
-	file descriptors according to what POSIX requires.
-
-     CLONE_SIGNAL
-	This flag selects the POSIX signal semantics.
-
-     CLONE_SETTLS
-	The sixth parameter to CLONE determines the TLS area for the
-	new thread.
-
-     CLONE_PARENT_SETTID
-	The kernels writes the thread ID of the newly created thread
-	into the location pointed to by the fifth parameters to CLONE.
-
-	Note that it would be semantically equivalent to use
-	CLONE_CHILD_SETTID but it is be more expensive in the kernel.
-
-     CLONE_CHILD_CLEARTID
-	The kernels clears the thread ID of a thread that has called
-	sys_exit() in the location pointed to by the seventh parameter
-	to CLONE.
-
-     The termination signal is chosen to be zero which means no signal
-     is sent.  */
-  int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL
-		     | CLONE_SETTLS | CLONE_PARENT_SETTID
-		     | CLONE_CHILD_CLEARTID | CLONE_SYSVSEM
-		     | 0);
-
-  if (__glibc_unlikely (THREAD_GETMEM (THREAD_SELF, report_events)))
-    {
-      /* The parent thread is supposed to report events.  Check whether
-	 the TD_CREATE event is needed, too.  */
-      const int _idx = __td_eventword (TD_CREATE);
-      const uint32_t _mask = __td_eventmask (TD_CREATE);
-
-      if ((_mask & (__nptl_threads_events.event_bits[_idx]
-		    | pd->eventbuf.eventmask.event_bits[_idx])) != 0)
-	{
-	  /* We always must have the thread start stopped.  */
-	  pd->stopped_start = true;
-
-	  /* Create the thread.  We always create the thread stopped
-	     so that it does not get far before we tell the debugger.  */
-	  int res = do_clone (pd, attr, clone_flags, start_thread,
-			      STACK_VARIABLES_ARGS, 1);
-	  if (res == 0)
-	    {
-	      /* Now fill in the information about the new thread in
-		 the newly created thread's data structure.  We cannot let
-		 the new thread do this since we don't know whether it was
-		 already scheduled when we send the event.  */
-	      pd->eventbuf.eventnum = TD_CREATE;
-	      pd->eventbuf.eventdata = pd;
-
-	      /* Enqueue the descriptor.  */
-	      do
-		pd->nextevent = __nptl_last_event;
-	      while (atomic_compare_and_exchange_bool_acq (&__nptl_last_event,
-							   pd, pd->nextevent)
-		     != 0);
-
-	      /* Now call the function which signals the event.  */
-	      __nptl_create_event ();
-
-	      /* And finally restart the new thread.  */
-	      lll_unlock (pd->lock, LLL_PRIVATE);
-	    }
-
-	  return res;
-	}
-    }
-
-#ifdef NEED_DL_SYSINFO
-  CHECK_THREAD_SYSINFO (pd);
-#endif
-
-  /* Determine whether the newly created threads has to be started
-     stopped since we have to set the scheduling parameters or set the
-     affinity.  */
-  bool stopped = false;
-  if (attr != NULL && (attr->cpuset != NULL
-		       || (attr->flags & ATTR_FLAG_NOTINHERITSCHED) != 0))
-    stopped = true;
-  pd->stopped_start = stopped;
-  pd->parent_cancelhandling = THREAD_GETMEM (THREAD_SELF, cancelhandling);
-
-  /* Actually create the thread.  */
-  int res = do_clone (pd, attr, clone_flags, start_thread,
-		      STACK_VARIABLES_ARGS, stopped);
-
-  if (res == 0 && stopped)
-    /* And finally restart the new thread.  */
-    lll_unlock (pd->lock, LLL_PRIVATE);
-
-  return res;
-}