Re: [PING][PATCH v3] Add pretty printers for the NPTL lock types

[Torvald Riegel <triegel at redhat dot com>]

I haven't checked consistency with glibc's implementation in detail.  I
really think we should have tests for that instead of having to do that
manually.

On Fri, 2015-11-13 at 18:50 -0300, Martin Galvan wrote:
> This patch adds the pretty-printers for the following NPTL types:
> 
> - pthread_mutex_t
> - pthread_mutexattr_t
> - pthread_cond_t
> - pthread_condattr_t
> - pthread_rwlock_t
> - pthread_rwlockattr_t
> 
> To load the pretty-printers into your gdb session, do the following:
> 
> python
> import sys
> sys.path.insert(0, '/path/to/glibc/build/')
> end
> source /path/to/glibc/install/bin/nptl-printers.py
> 
> You can check which printers are registered and enabled by issuing the
> 'info pretty-printer' gdb command. Printers should trigger automatically when
> trying to print a variable of one of the types mentioned above.
> 
> The printers are architecture-independent, and were tested on both the gdb CLI
> and Eclipse CDT.
> 
> In order to work, the printers need to know the values of various flags that
> are scattered throughout pthread.h and pthreadP.h as enums and #defines. Since
> replicating these constants in the printers file itself would create a
> maintenance burden, I followed Joseph Myers' advice and wrote a script
> called gen-py-const.awk that Makerules uses to extract the constants.
> This script is pretty much the same as gen-as-const.awk, except it doesn't cast
> the constant values to 'long' and is thorougly documented. The constants need
> only to be enumerated in a .pysym file, which is then referenced by a Make
> variable called gen-py-const-headers.

There is still a good amount of glibc implementation internals mirrored
in the pretty printers implementation.  It would be nice if this would
not be the case, but I haven't thought about whether/what might improve
this.

> diff --git a/nptl/nptl-printers.py b/nptl/nptl-printers.py
> new file mode 100644
> index 0000000..ce96fa9
> --- /dev/null
> +++ b/nptl/nptl-printers.py
> @@ -0,0 +1,629 @@
> +# Copyright (C) 2015 Free Software Foundation, Inc.
> +# This file is part of the GNU C Library.
> +# Contributed by Martin Galvan <martin.galvan@tallertechnologies.com>
> +#
> +# 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/>.
> +
> +"""Pretty printers for the NTPL lock types.
> +
> +This file contains the gdb pretty printers for the following types:
> +
> +    * pthread_mutex_t
> +    * pthread_mutexattr_t
> +    * pthread_cond_t
> +    * pthread_condattr_t
> +    * pthread_rwlock_t
> +    * pthread_rwlockattr_t
> +
> +You can check which printers are registered and enabled by issuing the
> +'info pretty-printer' gdb command.  Printers should trigger automatically when
> +trying to print a variable of one of the types mentioned above.
> +"""
> +
> +from __future__ import print_function
> +import itertools
> +import re
> +import sys
> +
> +import gdb
> +from nptl_lock_constants import *
> +
> +MUTEX_TYPES = {
> +    PTHREAD_MUTEX_NORMAL: ('Type', 'Normal'),
> +    PTHREAD_MUTEX_RECURSIVE: ('Type', 'Recursive'),
> +    PTHREAD_MUTEX_ERRORCHECK: ('Type', 'Error check'),
> +    PTHREAD_MUTEX_ADAPTIVE_NP: ('Type', 'Adaptive')
> +}
> +
> +class MutexPrinter(object):
> +    """Pretty printer for pthread_mutex_t."""
> +
> +    def __init__(self, mutex):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            mutex: A gdb.value representing a pthread_mutex_t.
> +        """
> +
> +        data = mutex['__data']
> +        self.lock = data['__lock']
> +        self.count = data['__count']
> +        self.owner = data['__owner']
> +        self.kind = data['__kind']
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_mutex_t.
> +        """
> +
> +        return 'pthread_mutex_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_mutex_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the mutex's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        self.read_type()
> +        self.read_status()
> +        self.read_attributes()
> +        self.read_misc_info()
> +
> +    def read_type(self):
> +        """Read the mutex's type."""
> +
> +        mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK
> +
> +        # mutex_type must be casted to int because it's a gdb.Value
> +        self.values.append(MUTEX_TYPES[int(mutex_type)])
> +
> +    def read_status(self):
> +        """Read the mutex's status.
> +
> +        For architectures which support lock elision, this method reads
> +        whether the mutex is actually locked (i.e. it may show it as unlocked
> +        even after calling pthread_mutex_lock).

Is an uncommitted transaction actually visible to debuggers?  It may if
the debugger is injecting code into the binary, so that no interrupt or
context switch happen.  It may also be visible if we have something like
a suspendable transaction, and the debugger thinks it can peek inside of
txns.  I believe that currently, we can assume that uncommitted state is
invisible even to the debugger.

Either way, "actually locked" in the comment isn't correct.  The mutex
is actually locked when using lock elision, it's just that this isn't
reflected in memory necessarily.

> +        """
> +
> +        if self.kind == PTHREAD_MUTEX_DESTROYED:
> +            self.values.append(('Status', 'Destroyed'))
> +        elif self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
> +            self.read_status_robust()
> +        else:
> +            self.read_status_no_robust()
> +
> +    def read_status_robust(self):
> +        """Read the status of a robust mutex.
> +
> +        In glibc robust mutexes are implemented in a very different way than
> +        non-robust ones.  This method reads their locking status,
> +        whether it may have waiters, their registered owner (if any),
> +        whether the owner is alive or not, and the status of the state
> +        they're protecting.
> +        """
> +
> +        if self.lock == PTHREAD_MUTEX_UNLOCKED:
> +            self.values.append(('Status', 'Unlocked'))
> +        else:
> +            if self.lock & FUTEX_WAITERS:
> +                self.values.append(('Status', 'Locked, possibly with waiters'))
> +            else:
> +                self.values.append(('Status', 'Locked, no waiters'))

I think those strings should consider that there might be waiters that
just spin.  When waiters register, it is because they want to wait using
futexes.  Right now, we don't spin, but this should change eventually,
or is already the case for adaptive mutexes.  I suggest changing the
strings to something like "locked, possibly with waiters" and "locked,
possibly no waiters" to reflect that.

> +            if self.lock & FUTEX_OWNER_DIED:
> +                self.values.append(('Owner ID', '%d (dead)' % self.owner))
> +            else:
> +                self.values.append(('Owner ID', self.lock & FUTEX_TID_MASK))
> +
> +        if self.owner == PTHREAD_MUTEX_INCONSISTENT:
> +            self.values.append(('State protected by this mutex',
> +                                'Inconsistent'))
> +        elif self.owner == PTHREAD_MUTEX_NOTRECOVERABLE:
> +            self.values.append(('State protected by this mutex',
> +                                'Not recoverable'))
> +
> +    def read_status_no_robust(self):
> +        """Read the status of a non-robust mutex.
> +
> +        Read info on whether the mutex is locked, if it may have waiters
> +        and its owner (if any).
> +        """
> +
> +        if self.lock == PTHREAD_MUTEX_UNLOCKED:
> +            self.values.append(('Status', 'Unlocked'))
> +        else:
> +            if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
> +                waiters = self.lock & FUTEX_WAITERS
> +                owner = self.lock & FUTEX_TID_MASK
> +            else:
> +                # Mutex protocol is PP or none
> +                waiters = (self.lock != PTHREAD_MUTEX_LOCKED_NO_WAITERS)
> +                owner = self.owner
> +
> +            if waiters:
> +                self.values.append(('Status', 'Locked, possibly with waiters'))
> +            else:
> +                self.values.append(('Status', 'Locked, no waiters'))
> +
> +            self.values.append(('Owner ID', owner))
> +
> +    def read_attributes(self):
> +        """Read the mutex's attributes."""
> +
> +        if self.kind != PTHREAD_MUTEX_DESTROYED:
> +            if self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
> +                self.values.append(('Robust', 'Yes'))
> +            else:
> +                self.values.append(('Robust', 'No'))
> +
> +            # In glibc, robust mutexes always have their pshared flag set to
> +            # 'shared' regardless of what the pshared flag of their
> +            # mutexattr was.  Therefore a robust mutex will act as shared
> +            # even if it was initialized with a 'private' mutexattr.
> +            if self.kind & PTHREAD_MUTEX_PSHARED_BIT:
> +                self.values.append(('Shared', 'Yes'))
> +            else:
> +                self.values.append(('Shared', 'No'))
> +
> +            if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
> +                self.values.append(('Protocol', 'Priority inherit'))
> +            elif self.kind & PTHREAD_MUTEX_PRIO_PROTECT_NP:
> +                prio_ceiling = ((self.lock & PTHREAD_MUTEX_PRIO_CEILING_MASK)
> +                                >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT)
> +
> +                self.values.append(('Protocol', 'Priority protect'))
> +                self.values.append(('Priority ceiling', prio_ceiling))
> +            else:
> +                # PTHREAD_PRIO_NONE
> +                self.values.append(('Protocol', 'None'))
> +
> +    def read_misc_info(self):
> +        """Read miscellaneous info on the mutex.
> +
> +        For now this reads the number of times a row a recursive mutex

s/a row//

> +        was locked by the same thread.
> +        """
> +
> +        mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK
> +
> +        if mutex_type == PTHREAD_MUTEX_RECURSIVE and self.count > 1:
> +            self.values.append(('Times locked recursively', self.count))
> +
> +class MutexAttributesPrinter(object):
> +    """Pretty printer for pthread_mutexattr_t.
> +
> +    In the NPTL this is a type that's always casted to struct pthread_mutexattr
> +    which has a single 'mutexkind' field containing the actual attributes.
> +    """
> +
> +    def __init__(self, mutexattr):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            mutexattr: A gdb.value representing a pthread_mutexattr_t.
> +        """
> +
> +        mutexattr_struct = gdb.lookup_type('struct pthread_mutexattr')
> +        self.mutexattr = mutexattr.cast(mutexattr_struct)['mutexkind']
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_mutexattr_t.
> +        """
> +
> +        return 'pthread_mutexattr_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_mutexattr_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the mutexattr's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        mutexattr_type = (self.mutexattr
> +                          & ~PTHREAD_MUTEXATTR_FLAG_BITS
> +                          & ~PTHREAD_MUTEX_NO_ELISION_NP)
> +
> +        # mutexattr_type must be casted to int because it's a gdb.Value
> +        self.values.append(MUTEX_TYPES[int(mutexattr_type)])
> +
> +        if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_ROBUST:
> +            self.values.append(('Robust', 'Yes'))
> +        else:
> +            self.values.append(('Robust', 'No'))
> +
> +        if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_PSHARED:
> +            self.values.append(('Shared', 'Yes'))
> +        else:
> +            self.values.append(('Shared', 'No'))
> +
> +        protocol = ((self.mutexattr & PTHREAD_MUTEXATTR_PROTOCOL_MASK) >>
> +                    PTHREAD_MUTEXATTR_PROTOCOL_SHIFT)
> +
> +        if protocol == PTHREAD_PRIO_NONE:
> +            self.values.append(('Protocol', 'None'))
> +        elif protocol == PTHREAD_PRIO_INHERIT:
> +            self.values.append(('Protocol', 'Priority inherit'))
> +        elif protocol == PTHREAD_PRIO_PROTECT:
> +            self.values.append(('Protocol', 'Priority protect'))
> +
> +class ConditionVariablePrinter(object):
> +    """Pretty printer for pthread_cond_t."""
> +
> +    def __init__(self, cond):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            cond: A gdb.value representing a pthread_cond_t.
> +        """
> +
> +        data = cond['__data']
> +        self.total_seq = data['__total_seq']
> +        self.mutex = data['__mutex']
> +        self.nwaiters = data['__nwaiters']
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_cond_t.
> +        """
> +
> +        return 'pthread_cond_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_cond_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the condvar's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        self.read_status()
> +        self.read_attributes()
> +        self.read_mutex_info()
> +
> +    def read_status(self):
> +        """Read the status of the condvar.
> +
> +        This method reads whether the condvar is destroyed and how many threads
> +        are waiting for it.
> +        """
> +
> +        if self.total_seq == PTHREAD_COND_DESTROYED:
> +            self.values.append(('Status', 'Destroyed'))
> +
> +        self.values.append(('Threads waiting for this condvar',
> +                            self.nwaiters >> COND_NWAITERS_SHIFT))

Generally, the same applies as for mutexes.  However, it's not the case
in the current condvar implementation, and we'll replace that before we
add any substantial spinning.

> +
> +    def read_attributes(self):
> +        """Read the condvar's attributes."""
> +
> +        clock_id = self.nwaiters & ((1 << COND_NWAITERS_SHIFT) - 1)
> +        shared = (self.mutex == PTHREAD_COND_SHARED)
> +
> +        if shared:
> +            self.values.append(('Shared', 'Yes'))
> +        else:
> +            self.values.append(('Shared', 'No'))
> +
> +        self.values.append(('Clock ID', clock_id))
> +
> +    def read_mutex_info(self):
> +        """Read the data of the mutex this condvar is bound to.
> +
> +        A pthread_cond_t's __data.__mutex member is a void * which
> +        must be casted to pthread_mutex_t *.  For shared condvars, this
> +        member isn't recorded and has a value of ~0l instead.
> +        """
> +
> +        if self.mutex and self.mutex != PTHREAD_COND_SHARED:
> +            mutex_type = gdb.lookup_type('pthread_mutex_t')
> +            mutex = self.mutex.cast(mutex_type.pointer()).dereference()
> +
> +            self.values.append(('Mutex', mutex))
> +
> +class ConditionVariableAttributesPrinter(object):
> +    """Pretty printer for pthread_condattr_t.
> +
> +    In the NPTL this is a type that's
> +    always casted to struct pthread_condattr, which has a single 'value' field
> +    containing the actual attributes.
> +    """
> +
> +    def __init__(self, condattr):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            condattr: A gdb.value representing a pthread_condattr_t.
> +        """
> +
> +        condattr_struct = gdb.lookup_type('struct pthread_condattr')
> +        self.condattr = condattr.cast(condattr_struct)['value']
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_condattr_t.
> +        """
> +
> +        return 'pthread_condattr_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_condattr_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the condattr's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        clock_id = self.condattr & ((1 << COND_NWAITERS_SHIFT) - 1)
> +
> +        if self.condattr & 1:
> +            self.values.append(('Shared', 'Yes'))
> +        else:
> +            self.values.append(('Shared', 'No'))
> +
> +        self.values.append(('Clock ID', clock_id))
> +
> +class RWLockPrinter(object):
> +    """Pretty printer for pthread_rwlock_t."""
> +
> +    def __init__(self, rwlock):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            rwlock: A gdb.value representing a pthread_rwlock_t.
> +        """
> +
> +        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.shared = data['__shared']
> +        self.prefers_writers = data['__flags']
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_rwlock_t.
> +        """
> +
> +        return 'pthread_rwlock_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_rwlock_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the rwlock's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        self.read_status()
> +        self.read_attributes()
> +
> +    def read_status(self):
> +        """Read the status of the rwlock."""
> +
> +        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))
> +        else:
> +            self.values.append(('Status', 'Unlocked'))
> +
> +        self.values.append(('Queued readers', self.queued_readers))
> +        self.values.append(('Queued writers', self.queued_writers))
> +
> +    def read_attributes(self):
> +        """Read the attributes of the rwlock."""
> +
> +        if self.shared:
> +            self.values.append(('Shared', 'Yes'))
> +        else:
> +            self.values.append(('Shared', 'No'))
> +
> +        if self.prefers_writers:
> +            self.values.append(('Prefers', 'Writers'))
> +        else:
> +            self.values.append(('Prefers', 'Readers'))
> +
> +class RWLockAttributesPrinter(object):
> +    """Pretty printer for pthread_rwlockattr_t.
> +
> +    In the NPTL this is a type that's always casted to
> +    struct pthread_rwlockattr, which has two fields ('lockkind' and 'pshared')
> +    containing the actual attributes.
> +    """
> +
> +    def __init__(self, rwlockattr):
> +        """Initialize the printer's internal data structures.
> +
> +        Args:
> +            rwlockattr: A gdb.value representing a pthread_rwlockattr_t.
> +        """
> +
> +        rwlockattr_struct = gdb.lookup_type('struct pthread_rwlockattr')
> +        self.rwlockattr = rwlockattr.cast(rwlockattr_struct)
> +        self.values = []
> +        self.read_values()
> +
> +    def to_string(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_rwlockattr_t.
> +        """
> +
> +        return 'pthread_rwlockattr_t'
> +
> +    def children(self):
> +        """gdb API function.
> +
> +        This is called from gdb when we try to print a pthread_rwlockattr_t.
> +        """
> +
> +        return itertools.chain(self.values)
> +
> +    def read_values(self):
> +        """Read the rwlockattr's info and store it in self.values.
> +
> +        The data contained in self.values will be returned by the Iterator
> +        created in self.children.
> +        """
> +
> +        rwlock_type = self.rwlockattr['lockkind']
> +        shared = self.rwlockattr['pshared']
> +
> +        if shared == PTHREAD_PROCESS_SHARED:
> +            self.values.append(('Shared', 'Yes'))
> +        else:
> +            # PTHREAD_PROCESS_PRIVATE
> +            self.values.append(('Shared', 'No'))
> +
> +        if rwlock_type == PTHREAD_RWLOCK_PREFER_READER_NP:
> +            self.values.append(('Prefers', 'Readers'))
> +        elif (rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NP or
> +              rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP):
> +            self.values.append(('Prefers', 'Writers'))
> +
> +class Printer(object):
> +    """Printer class which conforms to the gdb pretty printing interface."""
> +
> +    def __init__(self, name):
> +        self.name = name
> +        self.enabled = True
> +        self.subprinters = []
> +
> +    class Subprinter(object):
> +        """A regex-based printer.
> +
> +        Individual pretty-printers are registered as subprinters of a single
> +        Printer instance.
> +        """
> +
> +        def __init__(self, name, regex, callable_obj):
> +            """Initialize a pretty-printer.
> +
> +            Args:
> +                name: The name of the printer.
> +                regex: A regular expression.  When gdb tries to print a
> +                    variable whose type matches the regex, it'll trigger
> +                    this printer.
> +                callable_obj: A function or callable object that gdb will call
> +                    when trying to print some value.  It should return a
> +                    pretty-printer.
> +            """
> +            self.name = name
> +            self.regex = re.compile(regex)
> +            self.callable = callable_obj
> +            self.enabled = True
> +
> +    def add_subprinter(self, name, regex, callable_obj):
> +        """Register a regex-based subprinter."""
> +
> +        self.subprinters.append(self.Subprinter(name, regex, callable_obj))
> +
> +    def __call__(self, value):
> +        """gdb API function.
> +
> +        This is called when trying to print an inferior value from gdb.
> +        If a registered printer's regex matches the value's type, gdb will use
> +        the printer to print the value.
> +        """
> +
> +        type_name = value.type.name
> +
> +        if type_name:
> +            for subprinter in self.subprinters:
> +                if subprinter.enabled and subprinter.regex.match(type_name):
> +                    return subprinter.callable(value)
> +
> +        # Return None if we have no type name or if we can't find a subprinter
> +        # for the given type.
> +        return None
> +
> +def register(objfile):
> +    """Register the pretty printers within the given objfile."""
> +
> +    printer = Printer('Glibc pthread locks')
> +
> +    printer.add_subprinter('pthread_mutex_t', '^pthread_mutex_t$',
> +                           MutexPrinter)
> +    printer.add_subprinter('pthread_mutexattr_t', '^pthread_mutexattr_t$',
> +                           MutexAttributesPrinter)
> +    printer.add_subprinter('pthread_cond_t', '^pthread_cond_t$',
> +                           ConditionVariablePrinter)
> +    printer.add_subprinter('pthread_condattr_t', '^pthread_condattr_t$',
> +                           ConditionVariableAttributesPrinter)
> +    printer.add_subprinter('pthread_rwlock_t', '^pthread_rwlock_t$',
> +                           RWLockPrinter)
> +    printer.add_subprinter('pthread_rwlockattr_t', '^pthread_rwlockattr_t$',
> +                           RWLockAttributesPrinter)
> +
> +    gdb.printing.register_pretty_printer(objfile, printer)
> +
> +register(gdb.current_objfile())
> diff --git a/nptl/nptl_lock_constants.pysym b/nptl/nptl_lock_constants.pysym
> new file mode 100644
> index 0000000..c576822
> --- /dev/null
> +++ b/nptl/nptl_lock_constants.pysym
> @@ -0,0 +1,66 @@
> +#include <pthreadP.h>
> +
> +-- Mutex types
> +PTHREAD_MUTEX_KIND_MASK          PTHREAD_MUTEX_KIND_MASK_NP
> +PTHREAD_MUTEX_NORMAL
> +PTHREAD_MUTEX_RECURSIVE          PTHREAD_MUTEX_RECURSIVE_NP
> +PTHREAD_MUTEX_ERRORCHECK         PTHREAD_MUTEX_ERRORCHECK_NP
> +PTHREAD_MUTEX_ADAPTIVE_NP
> +
> +-- Mutex status
> +-- These are hardcoded all over the code; there are no enums/macros for them.
> +PTHREAD_MUTEX_DESTROYED         -1
> +PTHREAD_MUTEX_UNLOCKED           0
> +PTHREAD_MUTEX_LOCKED_NO_WAITERS  1
> +
> +-- For robust mutexes
> +PTHREAD_MUTEX_INCONSISTENT
> +PTHREAD_MUTEX_NOTRECOVERABLE
> +FUTEX_OWNER_DIED
> +
> +-- For robust and PI mutexes
> +FUTEX_WAITERS
> +FUTEX_TID_MASK
> +
> +-- Mutex attributes
> +PTHREAD_MUTEX_ROBUST_NORMAL_NP
> +PTHREAD_MUTEX_PRIO_INHERIT_NP
> +PTHREAD_MUTEX_PRIO_PROTECT_NP
> +PTHREAD_MUTEX_PSHARED_BIT
> +PTHREAD_MUTEX_PRIO_CEILING_SHIFT
> +PTHREAD_MUTEX_PRIO_CEILING_MASK
> +
> +-- Mutex attribute flags
> +PTHREAD_MUTEXATTR_PROTOCOL_SHIFT
> +PTHREAD_MUTEXATTR_PROTOCOL_MASK
> +PTHREAD_MUTEXATTR_PRIO_CEILING_MASK
> +PTHREAD_MUTEXATTR_FLAG_ROBUST
> +PTHREAD_MUTEXATTR_FLAG_PSHARED
> +PTHREAD_MUTEXATTR_FLAG_BITS
> +PTHREAD_MUTEX_NO_ELISION_NP
> +
> +-- Priority protocols
> +PTHREAD_PRIO_NONE
> +PTHREAD_PRIO_INHERIT
> +PTHREAD_PRIO_PROTECT
> +
> +-- These values are hardcoded as well:
> +-- Value of __mutex for shared condvars.
> +PTHREAD_COND_SHARED             ~0l

Will this do the right thing for 32b, 64b, and x32?