Add and use new glibc-internal futex API.

This adds new functions for futex operations, starting with wait,
abstimed_wait, reltimed_wait, wake.  They add documentation and error
checking according to the current draft of the Linux kernel futex manpage.

Waiting with absolute or relative timeouts is split into separate functions.
This allows for removing a few cases of code duplication in pthreads code,
which uses absolute timeouts; also, it allows us to put platform-specific
code to go from an absolute to a relative timeout into the platform-specific
futex abstractions..

Futex operations that can be canceled are also split out into separate
functions suffixed by "_cancelable".

There are separate versions for both Linux and NaCl; while they currently
differ only slightly, my expectation is that the separate versions of
lowlevellock-futex.h will eventually be merged into futex-internal.h
when we get to move the lll_ functions over to the new futex API.

2 files changed, 250 insertions, 2 deletions

diff --git a/sysdeps/nacl/exit-thread.h b/sysdeps/nacl/exit-thread.h
index c809405..915f93d 100644
--- a/sysdeps/nacl/exit-thread.h
+++ b/sysdeps/nacl/exit-thread.h
@@ -18,7 +18,7 @@
 
 #include <assert.h>
 #include <atomic.h>
-#include <lowlevellock.h>
+#include <futex-internal.h>
 #include <nacl-interfaces.h>
 #include <nptl/pthreadP.h>
 
@@ -64,7 +64,7 @@ __exit_thread (void)
       assert (NACL_EXITING_TID > 0);
 
       atomic_store_relaxed (&pd->tid, NACL_EXITING_TID);
-      lll_futex_wake (&pd->tid, 1, LLL_PRIVATE);
+      futex_wake ((unsigned int *) &pd->tid, 1, FUTEX_PRIVATE);
     }
 
   /* This clears PD->tid some time after the thread stack can never
diff --git a/sysdeps/nacl/futex-internal.h b/sysdeps/nacl/futex-internal.h
new file mode 100644
index 0000000..593bb9d
--- /dev/null
+++ b/sysdeps/nacl/futex-internal.h
@@ -0,0 +1,248 @@
+/* futex operations for glibc-internal use.  NaCl version.
+   Copyright (C) 2014-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef FUTEX_INTERNAL_H
+#define FUTEX_INTERNAL_H
+
+#include <sysdeps/nptl/futex-internal.h>
+#include <errno.h>
+#include <lowlevellock-futex.h>
+#include <nacl-interfaces.h>
+#include <nptl/pthreadP.h>
+
+/* See sysdeps/nptl/futex-internal.h for documentation; this file only
+   contains NaCl-specific comments.
+
+   There is no support yet for shared futexes nor for exact relative
+   timeouts.  */
+
+/* See sysdeps/nptl/futex-internal.h for constraints on the value of the
+   FUTEX_PRIVATE and FUTEX_SHARED constants.
+   Shared futexes are not yet supported, and we never allow clients to
+   actually request shared futexes.  Therefore, we do not need a different
+   value.  */
+#undef FUTEX_SHARED
+#define FUTEX_SHARED  FUTEX_PRIVATE
+
+/* FUTEX_SHARED is not yet supported.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  if (__glibc_likely (pshared == PTHREAD_PROCESS_PRIVATE))
+    return 0;
+  else if (pshared == PTHREAD_PROCESS_SHARED)
+    return ENOTSUP;
+  else
+    return EINVAL;
+}
+
+/* Relative timeouts are only emulated via absolute timeouts using the
+   system clock.  */
+static __always_inline bool
+futex_supports_exact_relative_timeouts (void)
+{
+  return false;
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait (unsigned int *futex_word, unsigned int expected, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
+		       int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *reltime, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *reltime, int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *abstime, int private)
+{
+  int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex_word,
+					     expected, abstime);
+  switch (err)
+    {
+    case 0:
+    case EAGAIN:
+    case EINTR:
+    case ETIMEDOUT:
+      return err;
+
+    case EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case EINVAL: /* Either due to wrong alignment or due to the timeout not
+		    being normalized.  Must have been caused by a glibc or
+		    application bug.  */
+    case ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *abstime, int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex_word,
+					     expected, abstime);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case EAGAIN:
+    case EINTR:
+    case ETIMEDOUT:
+      return err;
+
+    case EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case EINVAL: /* Either due to wrong alignment or due to the timeout not
+		    being normalized.  Must have been caused by a glibc or
+		    application bug.  */
+    case ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline void
+futex_wake (unsigned int *futex_word, int processes_to_wake, int private)
+{
+  int res = lll_futex_wake (futex_word, processes_to_wake, private);
+  /* No error.  Ignore the number of woken processes.  */
+  if (res >= 0)
+    return;
+  switch (res)
+    {
+    case -EFAULT: /* Could have happened due to memory reuse.  */
+    case -EINVAL: /* Could be either due to incorrect alignment (a bug in
+		     glibc or in the application) or due to memory being
+		     reused for a PI futex.  We cannot distinguish between the
+		     two causes, and one of them is correct use, so we do not
+		     act in this case.  */
+      return;
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+#endif  /* futex-internal.h */