/* Copyright (C) 2002-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

   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/>.  */

#include <assert.h>

#include <errno.h>

#include <stdlib.h>

#include "pthreadP.h"

#include <lowlevellock.h>

#ifndef lll_trylock_elision

#define lll_trylock_elision(a,t) lll_trylock(a)

#endif

#ifndef FORCE_ELISION

#define FORCE_ELISION(m, s)

#endif

int

__pthread_mutex_trylock (pthread_mutex_t *mutex)

{

  int oldval;

  pid_t id = THREAD_GETMEM (THREAD_SELF, tid);

  /* See concurrency notes regarding mutex type which is loaded from __kind

     in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h.  */

  switch (__builtin_expect (PTHREAD_MUTEX_TYPE_ELISION (mutex),

			    PTHREAD_MUTEX_TIMED_NP))

    {

      /* Recursive mutex.  */

    case PTHREAD_MUTEX_RECURSIVE_NP|PTHREAD_MUTEX_ELISION_NP:

    case PTHREAD_MUTEX_RECURSIVE_NP:

      /* Check whether we already hold the mutex.  */

      if (mutex->__data.__owner == id)

	{

	  /* Just bump the counter.  */

	  if (__glibc_unlikely (mutex->__data.__count + 1 == 0))

	    /* Overflow of the counter.  */

	    return EAGAIN;

	  ++mutex->__data.__count;

	  return 0;

	}

      if (lll_trylock (mutex->__data.__lock) == 0)

	{

	  /* Record the ownership.  */

	  mutex->__data.__owner = id;

	  mutex->__data.__count = 1;

	  ++mutex->__data.__nusers;

	  return 0;

	}

      break;

    case PTHREAD_MUTEX_TIMED_ELISION_NP:

    elision: __attribute__((unused))

      if (lll_trylock_elision (mutex->__data.__lock,

			       mutex->__data.__elision) != 0)

	break;

      /* Don't record the ownership.  */

      return 0;

    case PTHREAD_MUTEX_TIMED_NP:

      FORCE_ELISION (mutex, goto elision);

      /*FALL THROUGH*/

    case PTHREAD_MUTEX_ADAPTIVE_NP:

    case PTHREAD_MUTEX_ERRORCHECK_NP:

      if (lll_trylock (mutex->__data.__lock) != 0)

	break;

      /* Record the ownership.  */

      mutex->__data.__owner = id;

      ++mutex->__data.__nusers;

      return 0;

    case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:

    case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:

    case PTHREAD_MUTEX_ROBUST_NORMAL_NP:

    case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:

      THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,

		     &mutex->__data.__list.__next);

      /* We need to set op_pending before starting the operation.  Also

	 see comments at ENQUEUE_MUTEX.  */

      __asm ("" ::: "memory");

      oldval = mutex->__data.__lock;

      do

	{

	again:

	  if ((oldval & FUTEX_OWNER_DIED) != 0)

	    {

	      /* The previous owner died.  Try locking the mutex.  */

	      int newval = id | (oldval & FUTEX_WAITERS);

	      newval

		= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,

						       newval, oldval);

	      if (newval != oldval)

		{

		  oldval = newval;

		  goto again;

		}

	      /* We got the mutex.  */

	      mutex->__data.__count = 1;

	      /* But it is inconsistent unless marked otherwise.  */

	      mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;

	      /* We must not enqueue the mutex before we have acquired it.

		 Also see comments at ENQUEUE_MUTEX.  */

	      __asm ("" ::: "memory");

	      ENQUEUE_MUTEX (mutex);

	      /* We need to clear op_pending after we enqueue the mutex.  */

	      __asm ("" ::: "memory");

	      THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	      /* Note that we deliberately exist here.  If we fall

		 through to the end of the function __nusers would be

		 incremented which is not correct because the old

		 owner has to be discounted.  */

	      return EOWNERDEAD;

	    }

	  /* Check whether we already hold the mutex.  */

	  if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))

	    {

	      int kind = PTHREAD_MUTEX_TYPE (mutex);

	      if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)

		{

		  /* We do not need to ensure ordering wrt another memory

		     access.  Also see comments at ENQUEUE_MUTEX. */

		  THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,

				 NULL);

		  return EDEADLK;

		}

	      if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)

		{

		  /* We do not need to ensure ordering wrt another memory

		     access.  */

		  THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,

				 NULL);

		  /* Just bump the counter.  */

		  if (__glibc_unlikely (mutex->__data.__count + 1 == 0))

		    /* Overflow of the counter.  */

		    return EAGAIN;

		  ++mutex->__data.__count;

		  return 0;

		}

	    }

	  oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,

							id, 0);

	  if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)

	    {

	      /* We haven't acquired the lock as it is already acquired by

		 another owner.  We do not need to ensure ordering wrt another

		 memory access.  */

	      THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	      return EBUSY;

	    }

	  if (__builtin_expect (mutex->__data.__owner

				== PTHREAD_MUTEX_NOTRECOVERABLE, 0))

	    {

	      /* This mutex is now not recoverable.  */

	      mutex->__data.__count = 0;

	      if (oldval == id)

		lll_unlock (mutex->__data.__lock,

			    PTHREAD_ROBUST_MUTEX_PSHARED (mutex));

	      /* FIXME This violates the mutex destruction requirements.  See

		 __pthread_mutex_unlock_full.  */

	      THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	      return ENOTRECOVERABLE;

	    }

	}

      while ((oldval & FUTEX_OWNER_DIED) != 0);

      /* We must not enqueue the mutex before we have acquired it.

	 Also see comments at ENQUEUE_MUTEX.  */

      __asm ("" ::: "memory");

      ENQUEUE_MUTEX (mutex);

      /* We need to clear op_pending after we enqueue the mutex.  */

      __asm ("" ::: "memory");

      THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

      mutex->__data.__owner = id;

      ++mutex->__data.__nusers;

      mutex->__data.__count = 1;

      return 0;

    /* The PI support requires the Linux futex system call.  If that's not

       available, pthread_mutex_init should never have allowed the type to

       be set.  So it will get the default case for an invalid type.  */

#ifdef __NR_futex

    case PTHREAD_MUTEX_PI_RECURSIVE_NP:

    case PTHREAD_MUTEX_PI_ERRORCHECK_NP:

    case PTHREAD_MUTEX_PI_NORMAL_NP:

    case PTHREAD_MUTEX_PI_ADAPTIVE_NP:

    case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:

    case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:

    case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:

    case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:

      {

	int kind, robust;

	{

	  /* See concurrency notes regarding __kind in struct __pthread_mutex_s

	     in sysdeps/nptl/bits/thread-shared-types.h.  */

	  int mutex_kind = atomic_load_relaxed (&(mutex->__data.__kind));

	  kind = mutex_kind & PTHREAD_MUTEX_KIND_MASK_NP;

	  robust = mutex_kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;

	}

	if (robust)

	  {

	    /* Note: robust PI futexes are signaled by setting bit 0.  */

	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,

			   (void *) (((uintptr_t) &mutex->__data.__list.__next)

				     | 1));

	    /* We need to set op_pending before starting the operation.  Also

	       see comments at ENQUEUE_MUTEX.  */

	    __asm ("" ::: "memory");

	  }

	oldval = mutex->__data.__lock;

	/* Check whether we already hold the mutex.  */

	if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))

	  {

	    if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)

	      {

		/* We do not need to ensure ordering wrt another memory

		   access.  */

		THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

		return EDEADLK;

	      }

	    if (kind == PTHREAD_MUTEX_RECURSIVE_NP)

	      {

		/* We do not need to ensure ordering wrt another memory

		   access.  */

		THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

		/* Just bump the counter.  */

		if (__glibc_unlikely (mutex->__data.__count + 1 == 0))

		  /* Overflow of the counter.  */

		  return EAGAIN;

		++mutex->__data.__count;

		return 0;

	      }

	  }

	oldval

	  = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,

						 id, 0);

	if (oldval != 0)

	  {

	    if ((oldval & FUTEX_OWNER_DIED) == 0)

	      {

		/* We haven't acquired the lock as it is already acquired by

		   another owner.  We do not need to ensure ordering wrt another

		   memory access.  */

		THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

		return EBUSY;

	      }

	    assert (robust);

	    /* The mutex owner died.  The kernel will now take care of

	       everything.  */

	    int private = (robust

			   ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)

			   : PTHREAD_MUTEX_PSHARED (mutex));

	    INTERNAL_SYSCALL_DECL (__err);

	    int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,

				      __lll_private_flag (FUTEX_TRYLOCK_PI,

							  private), 0, 0);

	    if (INTERNAL_SYSCALL_ERROR_P (e, __err)

		&& INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)

	      {

		/* The kernel has not yet finished the mutex owner death.

		   We do not need to ensure ordering wrt another memory

		   access.  */

		THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

		return EBUSY;

	      }

	    oldval = mutex->__data.__lock;

	  }

	if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))

	  {

	    atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);

	    /* We got the mutex.  */

	    mutex->__data.__count = 1;

	    /* But it is inconsistent unless marked otherwise.  */

	    mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;

	    /* We must not enqueue the mutex before we have acquired it.

	       Also see comments at ENQUEUE_MUTEX.  */

	    __asm ("" ::: "memory");

	    ENQUEUE_MUTEX (mutex);

	    /* We need to clear op_pending after we enqueue the mutex.  */

	    __asm ("" ::: "memory");

	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	    /* Note that we deliberately exit here.  If we fall

	       through to the end of the function __nusers would be

	       incremented which is not correct because the old owner

	       has to be discounted.  */

	    return EOWNERDEAD;

	  }

	if (robust

	    && __builtin_expect (mutex->__data.__owner

				 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))

	  {

	    /* This mutex is now not recoverable.  */

	    mutex->__data.__count = 0;

	    INTERNAL_SYSCALL_DECL (__err);

	    INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,

			      __lll_private_flag (FUTEX_UNLOCK_PI,

						  PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),

			      0, 0);

	    /* To the kernel, this will be visible after the kernel has

	       acquired the mutex in the syscall.  */

	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	    return ENOTRECOVERABLE;

	  }

	if (robust)

	  {

	    /* We must not enqueue the mutex before we have acquired it.

	       Also see comments at ENQUEUE_MUTEX.  */

	    __asm ("" ::: "memory");

	    ENQUEUE_MUTEX_PI (mutex);

	    /* We need to clear op_pending after we enqueue the mutex.  */

	    __asm ("" ::: "memory");

	    THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);

	  }

	mutex->__data.__owner = id;

	++mutex->__data.__nusers;

	mutex->__data.__count = 1;

	return 0;

      }

#endif  /* __NR_futex.  */

    case PTHREAD_MUTEX_PP_RECURSIVE_NP:

    case PTHREAD_MUTEX_PP_ERRORCHECK_NP:

    case PTHREAD_MUTEX_PP_NORMAL_NP:

    case PTHREAD_MUTEX_PP_ADAPTIVE_NP:

      {

	/* See concurrency notes regarding __kind in struct __pthread_mutex_s

	   in sysdeps/nptl/bits/thread-shared-types.h.  */

	int kind = atomic_load_relaxed (&(mutex->__data.__kind))

	  & PTHREAD_MUTEX_KIND_MASK_NP;

	oldval = mutex->__data.__lock;

	/* Check whether we already hold the mutex.  */

	if (mutex->__data.__owner == id)

	  {

	    if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)

	      return EDEADLK;

	    if (kind == PTHREAD_MUTEX_RECURSIVE_NP)

	      {

		/* Just bump the counter.  */

		if (__glibc_unlikely (mutex->__data.__count + 1 == 0))

		  /* Overflow of the counter.  */

		  return EAGAIN;

		++mutex->__data.__count;

		return 0;

	      }

	  }

	int oldprio = -1, ceilval;

	do

	  {

	    int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)

			  >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;

	    if (__pthread_current_priority () > ceiling)

	      {

		if (oldprio != -1)

		  __pthread_tpp_change_priority (oldprio, -1);

		return EINVAL;

	      }

	    int retval = __pthread_tpp_change_priority (oldprio, ceiling);

	    if (retval)

	      return retval;

	    ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;

	    oldprio = ceiling;

	    oldval

	      = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,

						     ceilval | 1, ceilval);

	    if (oldval == ceilval)

	      break;

	  }

	while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);

	if (oldval != ceilval)

	  {

	    __pthread_tpp_change_priority (oldprio, -1);

	    break;

	  }

	assert (mutex->__data.__owner == 0);

	/* Record the ownership.  */

	mutex->__data.__owner = id;

	++mutex->__data.__nusers;

	mutex->__data.__count = 1;

	return 0;

      }

      break;

    default:

      /* Correct code cannot set any other type.  */

      return EINVAL;

    }

  return EBUSY;

}

#ifndef __pthread_mutex_trylock

#ifndef pthread_mutex_trylock

weak_alias (__pthread_mutex_trylock, pthread_mutex_trylock)

hidden_def (__pthread_mutex_trylock)

#endif

#endif