/* Handle general operations.

   Copyright (C) 1997-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   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 <aio.h>

#include <assert.h>

#include <errno.h>

#include <limits.h>

#include <pthread.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/param.h>

#include <sys/stat.h>

#include <sys/time.h>

#include <aio_misc.h>

#ifndef aio_create_helper_thread

# define aio_create_helper_thread __aio_create_helper_thread

extern inline int

__aio_create_helper_thread (pthread_t *threadp, void *(*tf) (void *), void *arg)

{

  pthread_attr_t attr;

  /* Make sure the thread is created detached.  */

  pthread_attr_init (&attr);

  pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

  int ret = pthread_create (threadp, &attr, tf, arg);

  (void) pthread_attr_destroy (&attr);

  return ret;

}

#endif

static void add_request_to_runlist (struct requestlist *newrequest);

/* Pool of request list entries.  */

static struct requestlist **pool;

/* Number of total and allocated pool entries.  */

static size_t pool_max_size;

static size_t pool_size;

/* We implement a two dimensional array but allocate each row separately.

   The macro below determines how many entries should be used per row.

   It should better be a power of two.  */

#define ENTRIES_PER_ROW	32

/* How many rows we allocate at once.  */

#define ROWS_STEP	8

/* List of available entries.  */

static struct requestlist *freelist;

/* List of request waiting to be processed.  */

static struct requestlist *runlist;

/* Structure list of all currently processed requests.  */

static struct requestlist *requests;

/* Number of threads currently running.  */

static int nthreads;

/* Number of threads waiting for work to arrive. */

static int idle_thread_count;

/* These are the values used to optimize the use of AIO.  The user can

   overwrite them by using the `aio_init' function.  */

static struct aioinit optim =

{

  20,	/* int aio_threads;	Maximal number of threads.  */

  64,	/* int aio_num;		Number of expected simultaneous requests. */

  0,

  0,

  0,

  0,

  1,

  0

};

/* Since the list is global we need a mutex protecting it.  */

pthread_mutex_t __aio_requests_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

/* When you add a request to the list and there are idle threads present,

   you signal this condition variable. When a thread finishes work, it waits

   on this condition variable for a time before it actually exits. */

pthread_cond_t __aio_new_request_notification = PTHREAD_COND_INITIALIZER;

/* Functions to handle request list pool.  */

static struct requestlist *

get_elem (void)

{

  struct requestlist *result;

  if (freelist == NULL)

    {

      struct requestlist *new_row;

      int cnt;

      assert (sizeof (struct aiocb) == sizeof (struct aiocb64));

      if (pool_size + 1 >= pool_max_size)

	{

	  size_t new_max_size = pool_max_size + ROWS_STEP;

	  struct requestlist **new_tab;

	  new_tab = (struct requestlist **)

	    realloc (pool, new_max_size * sizeof (struct requestlist *));

	  if (new_tab == NULL)

	    return NULL;

	  pool_max_size = new_max_size;

	  pool = new_tab;

	}

      /* Allocate the new row.  */

      cnt = pool_size == 0 ? optim.aio_num : ENTRIES_PER_ROW;

      new_row = (struct requestlist *) calloc (cnt,

					       sizeof (struct requestlist));

      if (new_row == NULL)

	return NULL;

      pool[pool_size++] = new_row;

      /* Put all the new entries in the freelist.  */

      do

	{

	  new_row->next_prio = freelist;

	  freelist = new_row++;

	}

      while (--cnt > 0);

    }

  result = freelist;

  freelist = freelist->next_prio;

  return result;

}

void

__aio_free_request (struct requestlist *elem)

{

  elem->running = no;

  elem->next_prio = freelist;

  freelist = elem;

}

struct requestlist *

__aio_find_req (aiocb_union *elem)

{

  struct requestlist *runp = requests;

  int fildes = elem->aiocb.aio_fildes;

  while (runp != NULL && runp->aiocbp->aiocb.aio_fildes < fildes)

    runp = runp->next_fd;

  if (runp != NULL)

    {

      if (runp->aiocbp->aiocb.aio_fildes != fildes)

	runp = NULL;

      else

	while (runp != NULL && runp->aiocbp != elem)

	  runp = runp->next_prio;

    }

  return runp;

}

struct requestlist *

__aio_find_req_fd (int fildes)

{

  struct requestlist *runp = requests;

  while (runp != NULL && runp->aiocbp->aiocb.aio_fildes < fildes)

    runp = runp->next_fd;

  return (runp != NULL && runp->aiocbp->aiocb.aio_fildes == fildes

	  ? runp : NULL);

}

void

__aio_remove_request (struct requestlist *last, struct requestlist *req,

		      int all)

{

  assert (req->running == yes || req->running == queued

	  || req->running == done);

  if (last != NULL)

    last->next_prio = all ? NULL : req->next_prio;

  else

    {

      if (all || req->next_prio == NULL)

	{

	  if (req->last_fd != NULL)

	    req->last_fd->next_fd = req->next_fd;

	  else

	    requests = req->next_fd;

	  if (req->next_fd != NULL)

	    req->next_fd->last_fd = req->last_fd;

	}

      else

	{

	  if (req->last_fd != NULL)

	    req->last_fd->next_fd = req->next_prio;

	  else

	    requests = req->next_prio;

	  if (req->next_fd != NULL)

	    req->next_fd->last_fd = req->next_prio;

	  req->next_prio->last_fd = req->last_fd;

	  req->next_prio->next_fd = req->next_fd;

	  /* Mark this entry as runnable.  */

	  req->next_prio->running = yes;

	}

      if (req->running == yes)

	{

	  struct requestlist *runp = runlist;

	  last = NULL;

	  while (runp != NULL)

	    {

	      if (runp == req)

		{

		  if (last == NULL)

		    runlist = runp->next_run;

		  else

		    last->next_run = runp->next_run;

		  break;

		}

	      last = runp;

	      runp = runp->next_run;

	    }

	}

    }

}

/* The thread handler.  */

static void *handle_fildes_io (void *arg);

/* User optimization.  */

void

__aio_init (const struct aioinit *init)

{

  /* Get the mutex.  */

  pthread_mutex_lock (&__aio_requests_mutex);

  /* Only allow writing new values if the table is not yet allocated.  */

  if (pool == NULL)

    {

      optim.aio_threads = init->aio_threads < 1 ? 1 : init->aio_threads;

      assert (powerof2 (ENTRIES_PER_ROW));

      optim.aio_num = (init->aio_num < ENTRIES_PER_ROW

		       ? ENTRIES_PER_ROW

		       : init->aio_num & ~(ENTRIES_PER_ROW - 1));

    }

  if (init->aio_idle_time != 0)

    optim.aio_idle_time = init->aio_idle_time;

  /* Release the mutex.  */

  pthread_mutex_unlock (&__aio_requests_mutex);

}

weak_alias (__aio_init, aio_init)

/* The main function of the async I/O handling.  It enqueues requests

   and if necessary starts and handles threads.  */

struct requestlist *

__aio_enqueue_request (aiocb_union *aiocbp, int operation)

{

  int result = 0;

  int policy, prio;

  struct sched_param param;

  struct requestlist *last, *runp, *newp;

  int running = no;

  if (operation == LIO_SYNC || operation == LIO_DSYNC)

    aiocbp->aiocb.aio_reqprio = 0;

  else if (aiocbp->aiocb.aio_reqprio < 0

#ifdef AIO_PRIO_DELTA_MAX

	   || aiocbp->aiocb.aio_reqprio > AIO_PRIO_DELTA_MAX

#endif

	   )

    {

      /* Invalid priority value.  */

      __set_errno (EINVAL);

      aiocbp->aiocb.__error_code = EINVAL;

      aiocbp->aiocb.__return_value = -1;

      return NULL;

    }

  /* Compute priority for this request.  */

  pthread_getschedparam (pthread_self (), &policy, ¶m;;

  prio = param.sched_priority - aiocbp->aiocb.aio_reqprio;

  /* Get the mutex.  */

  pthread_mutex_lock (&__aio_requests_mutex);

  last = NULL;

  runp = requests;

  /* First look whether the current file descriptor is currently

     worked with.  */

  while (runp != NULL

	 && runp->aiocbp->aiocb.aio_fildes < aiocbp->aiocb.aio_fildes)

    {

      last = runp;

      runp = runp->next_fd;

    }

  /* Get a new element for the waiting list.  */

  newp = get_elem ();

  if (newp == NULL)

    {

      pthread_mutex_unlock (&__aio_requests_mutex);

      __set_errno (EAGAIN);

      return NULL;

    }

  newp->aiocbp = aiocbp;

  newp->waiting = NULL;

  aiocbp->aiocb.__abs_prio = prio;

  aiocbp->aiocb.__policy = policy;

  aiocbp->aiocb.aio_lio_opcode = operation;

  aiocbp->aiocb.__error_code = EINPROGRESS;

  aiocbp->aiocb.__return_value = 0;

  if (runp != NULL

      && runp->aiocbp->aiocb.aio_fildes == aiocbp->aiocb.aio_fildes)

    {

      /* The current file descriptor is worked on.  It makes no sense

	 to start another thread since this new thread would fight

	 with the running thread for the resources.  But we also cannot

	 say that the thread processing this desriptor shall immediately

	 after finishing the current job process this request if there

	 are other threads in the running queue which have a higher

	 priority.  */

      /* Simply enqueue it after the running one according to the

	 priority.  */

      last = NULL;

      while (runp->next_prio != NULL

	     && runp->next_prio->aiocbp->aiocb.__abs_prio >= prio)

	{

	  last = runp;

	  runp = runp->next_prio;

	}

      newp->next_prio = runp->next_prio;

      runp->next_prio = newp;

      running = queued;

    }

  else

    {

      running = yes;

      /* Enqueue this request for a new descriptor.  */

      if (last == NULL)

	{

	  newp->last_fd = NULL;

	  newp->next_fd = requests;

	  if (requests != NULL)

	    requests->last_fd = newp;

	  requests = newp;

	}

      else

	{

	  newp->next_fd = last->next_fd;

	  newp->last_fd = last;

	  last->next_fd = newp;

	  if (newp->next_fd != NULL)

	    newp->next_fd->last_fd = newp;

	}

      newp->next_prio = NULL;

      last = NULL;

    }

  if (running == yes)

    {

      /* We try to create a new thread for this file descriptor.  The

	 function which gets called will handle all available requests

	 for this descriptor and when all are processed it will

	 terminate.

	 If no new thread can be created or if the specified limit of

	 threads for AIO is reached we queue the request.  */

      /* See if we need to and are able to create a thread.  */

      if (nthreads < optim.aio_threads && idle_thread_count == 0)

	{

	  pthread_t thid;

	  running = newp->running = allocated;

	  /* Now try to start a thread.  */

	  result = aio_create_helper_thread (&thid, handle_fildes_io, newp);

	  if (result == 0)

	    /* We managed to enqueue the request.  All errors which can

	       happen now can be recognized by calls to `aio_return' and

	       `aio_error'.  */

	    ++nthreads;

	  else

	    {

	      /* Reset the running flag.  The new request is not running.  */

	      running = newp->running = yes;

	      if (nthreads == 0)

		{

		  /* We cannot create a thread in the moment and there is

		     also no thread running.  This is a problem.  `errno' is

		     set to EAGAIN if this is only a temporary problem.  */

		  __aio_remove_request (last, newp, 0);

		}

	      else

		result = 0;

	    }

	}

    }

  /* Enqueue the request in the run queue if it is not yet running.  */

  if (running == yes && result == 0)

    {

      add_request_to_runlist (newp);

      /* If there is a thread waiting for work, then let it know that we

	 have just given it something to do. */

      if (idle_thread_count > 0)

	pthread_cond_signal (&__aio_new_request_notification);

    }

  if (result == 0)

    newp->running = running;

  else

    {

      /* Something went wrong.  */

      __aio_free_request (newp);

      aiocbp->aiocb.__error_code = result;

      __set_errno (result);

      newp = NULL;

    }

  /* Release the mutex.  */

  pthread_mutex_unlock (&__aio_requests_mutex);

  return newp;

}

static void *

handle_fildes_io (void *arg)

{

  pthread_t self = pthread_self ();

  struct sched_param param;

  struct requestlist *runp = (struct requestlist *) arg;

  aiocb_union *aiocbp;

  int policy;

  int fildes;

  pthread_getschedparam (self, &policy, ¶m;;

  do

    {

      /* If runp is NULL, then we were created to service the work queue

	 in general, not to handle any particular request. In that case we

	 skip the "do work" stuff on the first pass, and go directly to the

	 "get work off the work queue" part of this loop, which is near the

	 end. */

      if (runp == NULL)

	pthread_mutex_lock (&__aio_requests_mutex);

      else

	{

	  /* Hopefully this request is marked as running.  */

	  assert (runp->running == allocated);

	  /* Update our variables.  */

	  aiocbp = runp->aiocbp;

	  fildes = aiocbp->aiocb.aio_fildes;

	  /* Change the priority to the requested value (if necessary).  */

	  if (aiocbp->aiocb.__abs_prio != param.sched_priority

	      || aiocbp->aiocb.__policy != policy)

	    {

	      param.sched_priority = aiocbp->aiocb.__abs_prio;

	      policy = aiocbp->aiocb.__policy;

	      pthread_setschedparam (self, policy, ¶m;;

	    }

	  /* Process request pointed to by RUNP.  We must not be disturbed

	     by signals.  */

	  if ((aiocbp->aiocb.aio_lio_opcode & 127) == LIO_READ)

	    {

	      if (sizeof (off_t) != sizeof (off64_t)

		  && aiocbp->aiocb.aio_lio_opcode & 128)

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (__pread64 (fildes, (void *)

						 aiocbp->aiocb64.aio_buf,

						 aiocbp->aiocb64.aio_nbytes,

						 aiocbp->aiocb64.aio_offset));

	      else

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (__libc_pread (fildes,

						    (void *)

						    aiocbp->aiocb.aio_buf,

						    aiocbp->aiocb.aio_nbytes,

						    aiocbp->aiocb.aio_offset));

	      if (aiocbp->aiocb.__return_value == -1 && errno == ESPIPE)

		/* The Linux kernel is different from others.  It returns

		   ESPIPE if using pread on a socket.  Other platforms

		   simply ignore the offset parameter and behave like

		   read.  */

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (read (fildes,

					    (void *) aiocbp->aiocb64.aio_buf,

					    aiocbp->aiocb64.aio_nbytes));

	    }

	  else if ((aiocbp->aiocb.aio_lio_opcode & 127) == LIO_WRITE)

	    {

	      if (sizeof (off_t) != sizeof (off64_t)

		  && aiocbp->aiocb.aio_lio_opcode & 128)

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (__pwrite64 (fildes, (const void *)

						  aiocbp->aiocb64.aio_buf,

						  aiocbp->aiocb64.aio_nbytes,

						  aiocbp->aiocb64.aio_offset));

	      else

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (__libc_pwrite (fildes, (const void *)

					      aiocbp->aiocb.aio_buf,

					      aiocbp->aiocb.aio_nbytes,

					      aiocbp->aiocb.aio_offset));

	      if (aiocbp->aiocb.__return_value == -1 && errno == ESPIPE)

		/* The Linux kernel is different from others.  It returns

		   ESPIPE if using pwrite on a socket.  Other platforms

		   simply ignore the offset parameter and behave like

		   write.  */

		aiocbp->aiocb.__return_value =

		  TEMP_FAILURE_RETRY (write (fildes,

					     (void *) aiocbp->aiocb64.aio_buf,

					     aiocbp->aiocb64.aio_nbytes));

	    }

	  else if (aiocbp->aiocb.aio_lio_opcode == LIO_DSYNC)

	    aiocbp->aiocb.__return_value =

	      TEMP_FAILURE_RETRY (fdatasync (fildes));

	  else if (aiocbp->aiocb.aio_lio_opcode == LIO_SYNC)

	    aiocbp->aiocb.__return_value =

	      TEMP_FAILURE_RETRY (fsync (fildes));

	  else

	    {

	      /* This is an invalid opcode.  */

	      aiocbp->aiocb.__return_value = -1;

	      __set_errno (EINVAL);

	    }

	  /* Get the mutex.  */

	  pthread_mutex_lock (&__aio_requests_mutex);

	  if (aiocbp->aiocb.__return_value == -1)

	    aiocbp->aiocb.__error_code = errno;

	  else

	    aiocbp->aiocb.__error_code = 0;

	  /* Send the signal to notify about finished processing of the

	     request.  */

	  __aio_notify (runp);

	  /* For debugging purposes we reset the running flag of the

	     finished request.  */

	  assert (runp->running == allocated);

	  runp->running = done;

	  /* Now dequeue the current request.  */

	  __aio_remove_request (NULL, runp, 0);

	  if (runp->next_prio != NULL)

	    add_request_to_runlist (runp->next_prio);

	  /* Free the old element.  */

	  __aio_free_request (runp);

	}

      runp = runlist;

      /* If the runlist is empty, then we sleep for a while, waiting for

	 something to arrive in it. */

      if (runp == NULL && optim.aio_idle_time >= 0)

	{

	  struct timeval now;

	  struct timespec wakeup_time;

	  ++idle_thread_count;

	  __gettimeofday (&now, NULL);

	  wakeup_time.tv_sec = now.tv_sec + optim.aio_idle_time;

	  wakeup_time.tv_nsec = now.tv_usec * 1000;

	  if (wakeup_time.tv_nsec >= 1000000000)

	    {

	      wakeup_time.tv_nsec -= 1000000000;

	      ++wakeup_time.tv_sec;

	    }

	  pthread_cond_timedwait (&__aio_new_request_notification,

				  &__aio_requests_mutex,

				  &wakeup_time);

	  --idle_thread_count;

	  runp = runlist;

	}

      if (runp == NULL)

	--nthreads;

      else

	{

	  assert (runp->running == yes);

	  runp->running = allocated;

	  runlist = runp->next_run;

	  /* If we have a request to process, and there's still another in

	     the run list, then we need to either wake up or create a new

	     thread to service the request that is still in the run list. */

	  if (runlist != NULL)

	    {

	      /* There are at least two items in the work queue to work on.

		 If there are other idle threads, then we should wake them

		 up for these other work elements; otherwise, we should try

		 to create a new thread. */

	      if (idle_thread_count > 0)

		pthread_cond_signal (&__aio_new_request_notification);

	      else if (nthreads < optim.aio_threads)

		{

		  pthread_t thid;

		  pthread_attr_t attr;

		  /* Make sure the thread is created detached.  */

		  pthread_attr_init (&attr);

		  pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

		  /* Now try to start a thread. If we fail, no big deal,

		     because we know that there is at least one thread (us)

		     that is working on AIO operations. */

		  if (pthread_create (&thid, &attr, handle_fildes_io, NULL)

		      == 0)

		    ++nthreads;

		}

	    }

	}

      /* Release the mutex.  */

      pthread_mutex_unlock (&__aio_requests_mutex);

    }

  while (runp != NULL);

  return NULL;

}

/* Free allocated resources.  */

libc_freeres_fn (free_res)

{

  size_t row;

  for (row = 0; row < pool_max_size; ++row)

    free (pool[row]);

  free (pool);

}

/* Add newrequest to the runlist. The __abs_prio flag of newrequest must

   be correctly set to do this. Also, you had better set newrequest's

   "running" flag to "yes" before you release your lock or you'll throw an

   assertion. */

static void

add_request_to_runlist (struct requestlist *newrequest)

{

  int prio = newrequest->aiocbp->aiocb.__abs_prio;

  struct requestlist *runp;

  if (runlist == NULL || runlist->aiocbp->aiocb.__abs_prio < prio)

    {

      newrequest->next_run = runlist;

      runlist = newrequest;

    }

  else

    {

      runp = runlist;

      while (runp->next_run != NULL

	     && runp->next_run->aiocbp->aiocb.__abs_prio >= prio)

	runp = runp->next_run;

      newrequest->next_run = runp->next_run;

      runp->next_run = newrequest;

    }

}