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PR lib/38741 priority inversion in libpthread breaks apps that use
SCHED_FIFO threads

- Change condvar sync so that we never take the condvar's spinlock without
  first holding the caller-provided mutex. Previously, the spinlock was only
  taken without the mutex in an error path, but it was enough to trigger the
  problem described in the PR.

- Even with this change, applications calling pthread_cond_signal/broadcast
  without holding the interlocking mutex are still subject to the problem
  described in the PR. POSIX discourages this saying that it leads to
  undefined scheduling behaviour, which seems good enough for the time being.

- Elsewhere, use a hash of mutexes instead of per-object spinlocks to
  synchronize entry/exit from sleep queues.

- Simplify how sleep queues are maintained.

/*	$NetBSD: pthread_int.h,v 1.69 2008/05/25 17:05:28 ad Exp $	*/

/*-
 * Copyright (c) 2001, 2002, 2003, 2006, 2007, 2008 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Nathan J. Williams and Andrew Doran.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * NOTE: when changing anything in this file, please ensure that
 * libpthread_dbg still compiles.
 */

#ifndef _LIB_PTHREAD_INT_H
#define _LIB_PTHREAD_INT_H

/* #define PTHREAD__DEBUG */
#define ERRORCHECK

#include "pthread_types.h"
#include "pthread_queue.h"
#include "pthread_md.h"

/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"

#include <sys/atomic.h>
#include <sys/tree.h>

#include <lwp.h>
#include <signal.h>

#ifdef __GNUC__
#define	PTHREAD_HIDE	__attribute__ ((visibility("hidden")))
#else
#define	PTHREAD_HIDE	/* nothing */
#endif

#define PTHREAD_KEYS_MAX 	256
#define	PTHREAD__UNPARK_MAX	32

/*
 * The size of this structure needs to be no larger than struct
 * __pthread_cleanup_store, defined in pthread.h.
 */
struct pt_clean_t {
	PTQ_ENTRY(pt_clean_t)	ptc_next;
	void	(*ptc_cleanup)(void *);
	void	*ptc_arg;
};

/* Private data for pthread_attr_t */
struct pthread_attr_private {
	char ptap_name[PTHREAD_MAX_NAMELEN_NP];
	void *ptap_namearg;
	void *ptap_stackaddr;
	size_t ptap_stacksize;
	size_t ptap_guardsize;
};

struct pthread_lock_ops {
	void	(*plo_init)(__cpu_simple_lock_t *);
	int	(*plo_try)(__cpu_simple_lock_t *);
	void	(*plo_unlock)(__cpu_simple_lock_t *);
	void	(*plo_lock)(__cpu_simple_lock_t *);
};

struct	__pthread_st {
	pthread_t	pt_self;	/* Must be first. */
	unsigned int	pt_magic;	/* Magic number */
	int		pt_state;	/* running, blocked, etc. */
	pthread_mutex_t	pt_lock;	/* lock on state */
	int		pt_flags;	/* see PT_FLAG_* below */
	int		pt_cancel;	/* Deferred cancellation */
	int		pt_errno;	/* Thread-specific errno. */
	stack_t		pt_stack;	/* Our stack */
	void		*pt_exitval;	/* Read by pthread_join() */
	char		*pt_name;	/* Thread's name, set by the app. */
	int		pt_willpark;	/* About to park */
	lwpid_t		pt_unpark;	/* Unpark this when parking */
	struct pthread_lock_ops pt_lockops;/* Cached to avoid PIC overhead */
	pthread_mutex_t	*pt_droplock;	/* Drop this lock if cancelled */
	pthread_cond_t	pt_joiners;	/* Threads waiting to join. */

	/* Threads to defer waking, usually until pthread_mutex_unlock(). */
	lwpid_t		pt_waiters[PTHREAD__UNPARK_MAX];
	size_t		pt_nwaiters;

	/* Stack of cancellation cleanup handlers and their arguments */
	PTQ_HEAD(, pt_clean_t)	pt_cleanup_stack;

	/* LWP ID and entry on the list of all threads. */
	lwpid_t		pt_lid;
	RB_ENTRY(__pthread_st) pt_alltree;
	PTQ_ENTRY(__pthread_st) pt_allq;
	PTQ_ENTRY(__pthread_st)	pt_deadq;

	/*
	 * General synchronization data.  We try to align, as threads
	 * on other CPUs will access this data frequently.
	 */
	int		pt_dummy1 __aligned(128);
	struct lwpctl 	*pt_lwpctl;	/* Kernel/user comms area */
	volatile int	pt_blocking;	/* Blocking in userspace */
	volatile int	pt_rwlocked;	/* Handed rwlock successfully */
	volatile int	pt_signalled;	/* Received pthread_cond_signal() */
	volatile int	pt_mutexwait;	/* Waiting to acquire mutex */
	void * volatile pt_mutexnext;	/* Next thread in chain */
	void * volatile	pt_sleepobj;	/* Object slept on */
	PTQ_ENTRY(__pthread_st) pt_sleep;
	void		(*pt_early)(void *);
	int		pt_dummy2 __aligned(128);

	/* Thread-specific data.  Large so it sits close to the end. */
	int		pt_havespecific;
	void		*pt_specific[PTHREAD_KEYS_MAX];

	/*
	 * Context for thread creation.  At the end as it's cached
	 * and then only ever passed to _lwp_create(). 
	 */
	ucontext_t	pt_uc;
};

/* Thread states */
#define PT_STATE_RUNNING	1
#define PT_STATE_ZOMBIE		5
#define PT_STATE_DEAD		6

/* Flag values */

#define PT_FLAG_DETACHED	0x0001
#define PT_FLAG_CS_DISABLED	0x0004	/* Cancellation disabled */
#define PT_FLAG_CS_ASYNC	0x0008  /* Cancellation is async */
#define PT_FLAG_CS_PENDING	0x0010
#define PT_FLAG_SCOPE_SYSTEM	0x0040
#define PT_FLAG_EXPLICIT_SCHED	0x0080
#define PT_FLAG_SUSPENDED	0x0100	/* In the suspended queue */

#define PT_MAGIC	0x11110001
#define PT_DEAD		0xDEAD0001

#define PT_ATTR_MAGIC	0x22220002
#define PT_ATTR_DEAD	0xDEAD0002

extern int	pthread__stacksize_lg;
extern size_t	pthread__stacksize;
extern vaddr_t	pthread__stackmask;
extern vaddr_t	pthread__threadmask;
extern int	pthread__nspins;
extern int	pthread__concurrency;
extern int 	pthread__osrev;
extern int 	pthread__unpark_max;

/* Flag to be used in a ucontext_t's uc_flags indicating that
 * the saved register state is "user" state only, not full
 * trap state.
 */
#define _UC_USER_BIT		30
#define _UC_USER		(1LU << _UC_USER_BIT)

/* Utility functions */
void	pthread__unpark_all(pthread_queue_t *, pthread_t, pthread_mutex_t *)
    PTHREAD_HIDE;
void	pthread__unpark(pthread_queue_t *, pthread_t, pthread_mutex_t *)
    PTHREAD_HIDE;
int	pthread__park(pthread_t, pthread_mutex_t *, pthread_queue_t *,
		      const struct timespec *, int, const void *)
		      PTHREAD_HIDE;
pthread_mutex_t *pthread__hashlock(volatile const void *) PTHREAD_HIDE;

/* Internal locking primitives */
void	pthread__lockprim_init(void) PTHREAD_HIDE;
void	pthread_lockinit(pthread_spin_t *) PTHREAD_HIDE;

static inline void pthread__spinlock(pthread_t, pthread_spin_t *)
    __attribute__((__always_inline__));
static inline void
pthread__spinlock(pthread_t self, pthread_spin_t *lock)
{
	if (__predict_true((*self->pt_lockops.plo_try)(lock)))
		return;
	(*self->pt_lockops.plo_lock)(lock);
}

static inline int pthread__spintrylock(pthread_t, pthread_spin_t *)
    __attribute__((__always_inline__));
static inline int
pthread__spintrylock(pthread_t self, pthread_spin_t *lock)
{
	return (*self->pt_lockops.plo_try)(lock);
}

static inline void pthread__spinunlock(pthread_t, pthread_spin_t *)
    __attribute__((__always_inline__));
static inline void
pthread__spinunlock(pthread_t self, pthread_spin_t *lock)
{
	(*self->pt_lockops.plo_unlock)(lock);
}

extern const struct pthread_lock_ops *pthread__lock_ops;

int	pthread__simple_locked_p(__cpu_simple_lock_t *) PTHREAD_HIDE;
#define	pthread__simple_lock_init(alp)	(*pthread__lock_ops->plo_init)(alp)
#define	pthread__simple_lock_try(alp)	(*pthread__lock_ops->plo_try)(alp)
#define	pthread__simple_unlock(alp)	(*pthread__lock_ops->plo_unlock)(alp)

#ifndef _getcontext_u
int	_getcontext_u(ucontext_t *) PTHREAD_HIDE;
#endif
#ifndef _setcontext_u
int	_setcontext_u(const ucontext_t *) PTHREAD_HIDE;
#endif
#ifndef _swapcontext_u
int	_swapcontext_u(ucontext_t *, const ucontext_t *) PTHREAD_HIDE;
#endif

void	pthread__testcancel(pthread_t) PTHREAD_HIDE;
int	pthread__find(pthread_t) PTHREAD_HIDE;

#ifndef PTHREAD_MD_INIT
#define PTHREAD_MD_INIT
#endif

#ifndef _INITCONTEXT_U_MD
#define _INITCONTEXT_U_MD(ucp)
#endif

#define _INITCONTEXT_U(ucp) do {					\
	(ucp)->uc_flags = _UC_CPU | _UC_STACK;				\
	_INITCONTEXT_U_MD(ucp)						\
	} while (/*CONSTCOND*/0)

/* Stack location of pointer to a particular thread */
#define pthread__id(sp) \
	((pthread_t) (((vaddr_t)(sp)) & pthread__threadmask))

#ifdef PTHREAD__HAVE_THREADREG
#define	pthread__self()		pthread__threadreg_get()
#else
#define pthread__self() 	(pthread__id(pthread__sp()))
#endif

#define pthread__abort()						\
	pthread__assertfunc(__FILE__, __LINE__, __func__, "unreachable")

#define pthread__assert(e) do {						\
	if (__predict_false(!(e)))					\
       	       pthread__assertfunc(__FILE__, __LINE__, __func__, #e);	\
        } while (/*CONSTCOND*/0)

#define pthread__error(err, msg, e) do {				\
	if (__predict_false(!(e))) {					\
       	       pthread__errorfunc(__FILE__, __LINE__, __func__, msg);	\
	       return (err);						\
	} 								\
        } while (/*CONSTCOND*/0)

void	pthread__destroy_tsd(pthread_t) PTHREAD_HIDE;
void	pthread__assertfunc(const char *, int, const char *, const char *)
			    PTHREAD_HIDE;
void	pthread__errorfunc(const char *, int, const char *, const char *)
			   PTHREAD_HIDE;
char	*pthread__getenv(const char *) PTHREAD_HIDE;
void	pthread__cancelled(void) PTHREAD_HIDE;
void	pthread__mutex_deferwake(pthread_t, pthread_mutex_t *) PTHREAD_HIDE;

#ifndef pthread__smt_pause
#define	pthread__smt_pause()	/* nothing */
#endif

/*
 * Bits in the owner field of the lock that indicate lock state.  If the
 * WRITE_LOCKED bit is clear, then the owner field is actually a count of
 * the number of readers.
 */
#define	RW_HAS_WAITERS		0x01	/* lock has waiters */
#define	RW_WRITE_WANTED		0x02	/* >= 1 waiter is a writer */
#define	RW_WRITE_LOCKED		0x04	/* lock is currently write locked */
#define	RW_UNUSED		0x08	/* currently unused */

#define	RW_FLAGMASK		0x0f

#define	RW_READ_COUNT_SHIFT	4
#define	RW_READ_INCR		(1 << RW_READ_COUNT_SHIFT)
#define	RW_THREAD		((uintptr_t)-RW_READ_INCR)
#define	RW_OWNER(rw)		((rw)->rw_owner & RW_THREAD)
#define	RW_COUNT(rw)		((rw)->rw_owner & RW_THREAD)
#define	RW_FLAGS(rw)		((rw)->rw_owner & ~RW_THREAD)

#endif /* _LIB_PTHREAD_INT_H */