New pthread rwlock that is more scalable.

This replaces the pthread rwlock with a new implementation that uses a
more scalable algorithm (primarily through not using a critical section
anymore to make state changes).  The fast path for rdlock acquisition and
release is now basically a single atomic read-modify write or CAS and a few
branches.  See nptl/pthread_rwlock_common.c for details.

	* nptl/DESIGN-rwlock.txt: Remove.
	* nptl/lowlevelrwlock.sym: Remove.
	* nptl/Makefile: Add new tests.
	* nptl/pthread_rwlock_common.c: New file.  Contains the new rwlock.
	* nptl/pthreadP.h (PTHREAD_RWLOCK_PREFER_READER_P): Remove.
	(PTHREAD_RWLOCK_WRPHASE, PTHREAD_RWLOCK_WRLOCKED,
	PTHREAD_RWLOCK_RWAITING, PTHREAD_RWLOCK_READER_SHIFT,
	PTHREAD_RWLOCK_READER_OVERFLOW, PTHREAD_RWLOCK_WRHANDOVER,
	PTHREAD_RWLOCK_FUTEX_USED): New.
	* nptl/pthread_rwlock_init.c (__pthread_rwlock_init): Adapt to new
	implementation.
	* nptl/pthread_rwlock_rdlock.c (__pthread_rwlock_rdlock_slow): Remove.
	(__pthread_rwlock_rdlock): Adapt.
	* nptl/pthread_rwlock_timedrdlock.c
	(pthread_rwlock_timedrdlock): Adapt.
	* nptl/pthread_rwlock_timedwrlock.c
	(pthread_rwlock_timedwrlock): Adapt.
	* nptl/pthread_rwlock_trywrlock.c (pthread_rwlock_trywrlock): Adapt.
	* nptl/pthread_rwlock_tryrdlock.c (pthread_rwlock_tryrdlock): Adapt.
	* nptl/pthread_rwlock_unlock.c (pthread_rwlock_unlock): Adapt.
	* nptl/pthread_rwlock_wrlock.c (__pthread_rwlock_wrlock_slow): Remove.
	(__pthread_rwlock_wrlock): Adapt.
	* nptl/tst-rwlock10.c: Adapt.
	* nptl/tst-rwlock11.c: Adapt.
	* nptl/tst-rwlock17.c: New file.
	* nptl/tst-rwlock18.c: New file.
	* nptl/tst-rwlock19.c: New file.
	* nptl/tst-rwlock2b.c: New file.
	* nptl/tst-rwlock8.c: Adapt.
	* nptl/tst-rwlock9.c: Adapt.
	* sysdeps/aarch64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/arm/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/hppa/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/ia64/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/m68k/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/microblaze/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/mips/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/nios2/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/s390/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/sh/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/sparc/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/tile/nptl/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* sysdeps/unix/sysv/linux/alpha/bits/pthreadtypes.h
	(pthread_rwlock_t): Adapt.
	* sysdeps/unix/sysv/linux/powerpc/bits/pthreadtypes.h
	(pthread_rwlock_t): Adapt.
	* sysdeps/x86/bits/pthreadtypes.h (pthread_rwlock_t): Adapt.
	* nptl/nptl-printers.py (): Adapt.
	* nptl/nptl_lock_constants.pysym: Adapt.
	* nptl/test-rwlock-printers.py: Adapt.
	* nptl/test-rwlockattr-printers.c: Adapt.
	* nptl/test-rwlockattr-printers.py: Adapt.

nptl/nptl-printers.py

@@ -430,12 +430,10 @@ class RWLockPrinter(object):
         """
 
         data = rwlock['__data']
-        self.readers = data['__nr_readers']
-        self.queued_readers = data['__nr_readers_queued']
-        self.queued_writers = data['__nr_writers_queued']
-        self.writer_id = data['__writer']
+        self.readers = data['__readers']
+        self.cur_writer = data['__cur_writer']
         self.shared = data['__shared']
-        self.prefers_writers = data['__flags']
+        self.flags = data['__flags']
         self.values = []
         self.read_values()
 
@@ -468,20 +466,19 @@ class RWLockPrinter(object):
     def read_status(self):
         """Read the status of the rwlock."""
 
-        # Right now pthread_rwlock_destroy doesn't do anything, so there's no
-        # way to check if an rwlock is destroyed.
-
-        if self.writer_id:
-            self.values.append(('Status', 'Locked (Write)'))
-            self.values.append(('Writer ID', self.writer_id))
-        elif self.readers:
-            self.values.append(('Status', 'Locked (Read)'))
-            self.values.append(('Readers', self.readers))
+        if self.readers & PTHREAD_RWLOCK_WRPHASE:
+            if self.readers & PTHREAD_RWLOCK_WRLOCKED:
+                self.values.append(('Status', 'Acquired (Write)'))
+                self.values.append(('Writer ID', self.cur_writer))
+            else:
+                self.values.append(('Status', 'Not acquired'))
         else:
-            self.values.append(('Status', 'Unlocked'))
-
-        self.values.append(('Queued readers', self.queued_readers))
-        self.values.append(('Queued writers', self.queued_writers))
+            r = self.readers >> PTHREAD_RWLOCK_READER_SHIFT
+            if r > 0:
+                self.values.append(('Status', 'Acquired (Read)'))
+                self.values.append(('Readers', r))
+            else:
+                self.values.append(('Status', 'Not acquired'))
 
     def read_attributes(self):
         """Read the attributes of the rwlock."""
@@ -491,10 +488,12 @@ class RWLockPrinter(object):
         else:
             self.values.append(('Shared', 'No'))
 
-        if self.prefers_writers:
+        if self.flags == PTHREAD_RWLOCK_PREFER_READER_NP:
+            self.values.append(('Prefers', 'Readers'))
+        elif self.flags == PTHREAD_RWLOCK_PREFER_WRITER_NP:
             self.values.append(('Prefers', 'Writers'))
         else:
-            self.values.append(('Prefers', 'Readers'))
+            self.values.append(('Prefers', 'Writers no recursive readers'))
 
 class RWLockAttributesPrinter(object):
     """Pretty printer for pthread_rwlockattr_t.
@@ -555,13 +554,12 @@ class RWLockAttributesPrinter(object):
             # PTHREAD_PROCESS_PRIVATE
             self.values.append(('Shared', 'No'))
 
-        if (rwlock_type == PTHREAD_RWLOCK_PREFER_READER_NP or
-            rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NP):
-            # This is a known bug.  Using PTHREAD_RWLOCK_PREFER_WRITER_NP will
-            # still make the rwlock prefer readers.
+        if rwlock_type == PTHREAD_RWLOCK_PREFER_READER_NP:
             self.values.append(('Prefers', 'Readers'))
-        elif rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP:
+        elif rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NP:
             self.values.append(('Prefers', 'Writers'))
+        else:
+            self.values.append(('Prefers', 'Writers no recursive readers'))
 
 def register(objfile):
     """Register the pretty printers within the given objfile."""