glibc/sysdeps/pthread/aio_misc.c
Ulrich Drepper 584715c3a9 Fix AIO when thread creation failed.
Several bugs fixed when we needed to create a thread to work on AIO
requests but failed and there is not one running.
2009-10-29 21:01:24 -07:00

735 lines
20 KiB
C

/* Handle general operations.
Copyright (C) 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2006, 2007, 2009
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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <aio.h>
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.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 simultanious 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
internal_function
__aio_free_request (struct requestlist *elem)
{
elem->running = no;
elem->next_prio = freelist;
freelist = elem;
}
struct requestlist *
internal_function
__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 *
internal_function
__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
internal_function
__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;
optim.aio_num = (init->aio_num < ENTRIES_PER_ROW
? ENTRIES_PER_ROW
: init->aio_num & ~ENTRIES_PER_ROW);
}
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 *
internal_function
__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
|| aiocbp->aiocb.aio_reqprio > AIO_PRIO_DELTA_MAX)
{
/* 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, &param);
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;
#ifdef BROKEN_THREAD_SIGNALS
newp->caller_pid = (aiocbp->aiocb.aio_sigevent.sigev_notify == SIGEV_SIGNAL
? getpid () : 0);
#endif
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, &param);
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, &param);
}
/* 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 (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);
/* In theory we would need here a write memory barrier since the
callers test using aio_error() whether the request finished
and once this value != EINPROGRESS the field __return_value
must be committed to memory.
But since the pthread_mutex_lock call involves write memory
barriers as well it is not necessary. */
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;
}
}