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/*-
* Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
* Copyright (c) 2008-2009, Lawrence Stewart <lstewart@freebsd.org>
* Copyright (c) 2009-2010, The FreeBSD Foundation
* All rights reserved.
*
* Portions of this software were developed at the Centre for Advanced
* Internet Architectures, Swinburne University of Technology, Melbourne,
* Australia by Lawrence Stewart under sponsorship from the FreeBSD Foundation.
*
* 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 unmodified, 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 AUTHOR ``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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: release/9.1.0/sys/kern/kern_alq.c 207223 2010-04-26 13:48:22Z lstewart $");
#include "opt_mac.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/alq.h>
#include <sys/malloc.h>
#include <sys/unistd.h>
#include <sys/fcntl.h>
#include <sys/eventhandler.h>
#include <security/mac/mac_framework.h>
/* Async. Logging Queue */
struct alq {
char *aq_entbuf; /* Buffer for stored entries */
int aq_entmax; /* Max entries */
int aq_entlen; /* Entry length */
int aq_freebytes; /* Bytes available in buffer */
int aq_buflen; /* Total length of our buffer */
int aq_writehead; /* Location for next write */
int aq_writetail; /* Flush starts at this location */
int aq_wrapearly; /* # bytes left blank at end of buf */
int aq_flags; /* Queue flags */
int aq_waiters; /* Num threads waiting for resources
* NB: Used as a wait channel so must
* not be first field in the alq struct
*/
struct ale aq_getpost; /* ALE for use by get/post */
struct mtx aq_mtx; /* Queue lock */
struct vnode *aq_vp; /* Open vnode handle */
struct ucred *aq_cred; /* Credentials of the opening thread */
LIST_ENTRY(alq) aq_act; /* List of active queues */
LIST_ENTRY(alq) aq_link; /* List of all queues */
};
#define AQ_WANTED 0x0001 /* Wakeup sleeper when io is done */
#define AQ_ACTIVE 0x0002 /* on the active list */
#define AQ_FLUSHING 0x0004 /* doing IO */
#define AQ_SHUTDOWN 0x0008 /* Queue no longer valid */
#define AQ_ORDERED 0x0010 /* Queue enforces ordered writes */
#define AQ_LEGACY 0x0020 /* Legacy queue (fixed length writes) */
#define ALQ_LOCK(alq) mtx_lock_spin(&(alq)->aq_mtx)
#define ALQ_UNLOCK(alq) mtx_unlock_spin(&(alq)->aq_mtx)
#define HAS_PENDING_DATA(alq) ((alq)->aq_freebytes != (alq)->aq_buflen)
static MALLOC_DEFINE(M_ALD, "ALD", "ALD");
/*
* The ald_mtx protects the ald_queues list and the ald_active list.
*/
static struct mtx ald_mtx;
static LIST_HEAD(, alq) ald_queues;
static LIST_HEAD(, alq) ald_active;
static int ald_shutingdown = 0;
struct thread *ald_thread;
static struct proc *ald_proc;
#define ALD_LOCK() mtx_lock(&ald_mtx)
#define ALD_UNLOCK() mtx_unlock(&ald_mtx)
/* Daemon functions */
static int ald_add(struct alq *);
static int ald_rem(struct alq *);
static void ald_startup(void *);
static void ald_daemon(void);
static void ald_shutdown(void *, int);
static void ald_activate(struct alq *);
static void ald_deactivate(struct alq *);
/* Internal queue functions */
static void alq_shutdown(struct alq *);
static void alq_destroy(struct alq *);
static int alq_doio(struct alq *);
/*
* Add a new queue to the global list. Fail if we're shutting down.
*/
static int
ald_add(struct alq *alq)
{
int error;
error = 0;
ALD_LOCK();
if (ald_shutingdown) {
error = EBUSY;
goto done;
}
LIST_INSERT_HEAD(&ald_queues, alq, aq_link);
done:
ALD_UNLOCK();
return (error);
}
/*
* Remove a queue from the global list unless we're shutting down. If so,
* the ald will take care of cleaning up it's resources.
*/
static int
ald_rem(struct alq *alq)
{
int error;
error = 0;
ALD_LOCK();
if (ald_shutingdown) {
error = EBUSY;
goto done;
}
LIST_REMOVE(alq, aq_link);
done:
ALD_UNLOCK();
return (error);
}
/*
* Put a queue on the active list. This will schedule it for writing.
*/
static void
ald_activate(struct alq *alq)
{
LIST_INSERT_HEAD(&ald_active, alq, aq_act);
wakeup(&ald_active);
}
static void
ald_deactivate(struct alq *alq)
{
LIST_REMOVE(alq, aq_act);
alq->aq_flags &= ~AQ_ACTIVE;
}
static void
ald_startup(void *unused)
{
mtx_init(&ald_mtx, "ALDmtx", NULL, MTX_DEF|MTX_QUIET);
LIST_INIT(&ald_queues);
LIST_INIT(&ald_active);
}
static void
ald_daemon(void)
{
int needwakeup;
struct alq *alq;
ald_thread = FIRST_THREAD_IN_PROC(ald_proc);
EVENTHANDLER_REGISTER(shutdown_pre_sync, ald_shutdown, NULL,
SHUTDOWN_PRI_FIRST);
ALD_LOCK();
for (;;) {
while ((alq = LIST_FIRST(&ald_active)) == NULL &&
!ald_shutingdown)
mtx_sleep(&ald_active, &ald_mtx, PWAIT, "aldslp", 0);
/* Don't shutdown until all active ALQs are flushed. */
if (ald_shutingdown && alq == NULL) {
ALD_UNLOCK();
break;
}
ALQ_LOCK(alq);
ald_deactivate(alq);
ALD_UNLOCK();
needwakeup = alq_doio(alq);
ALQ_UNLOCK(alq);
if (needwakeup)
wakeup_one(alq);
ALD_LOCK();
}
kproc_exit(0);
}
static void
ald_shutdown(void *arg, int howto)
{
struct alq *alq;
ALD_LOCK();
/* Ensure no new queues can be created. */
ald_shutingdown = 1;
/* Shutdown all ALQs prior to terminating the ald_daemon. */
while ((alq = LIST_FIRST(&ald_queues)) != NULL) {
LIST_REMOVE(alq, aq_link);
ALD_UNLOCK();
alq_shutdown(alq);
ALD_LOCK();
}
/* At this point, all ALQs are flushed and shutdown. */
/*
* Wake ald_daemon so that it exits. It won't be able to do
* anything until we mtx_sleep because we hold the ald_mtx.
*/
wakeup(&ald_active);
/* Wait for ald_daemon to exit. */
mtx_sleep(ald_proc, &ald_mtx, PWAIT, "aldslp", 0);
ALD_UNLOCK();
}
static void
alq_shutdown(struct alq *alq)
{
ALQ_LOCK(alq);
/* Stop any new writers. */
alq->aq_flags |= AQ_SHUTDOWN;
/*
* If the ALQ isn't active but has unwritten data (possible if
* the ALQ_NOACTIVATE flag has been used), explicitly activate the
* ALQ here so that the pending data gets flushed by the ald_daemon.
*/
if (!(alq->aq_flags & AQ_ACTIVE) && HAS_PENDING_DATA(alq)) {
alq->aq_flags |= AQ_ACTIVE;
ALQ_UNLOCK(alq);
ALD_LOCK();
ald_activate(alq);
ALD_UNLOCK();
ALQ_LOCK(alq);
}
/* Drain IO */
while (alq->aq_flags & AQ_ACTIVE) {
alq->aq_flags |= AQ_WANTED;
msleep_spin(alq, &alq->aq_mtx, "aldclose", 0);
}
ALQ_UNLOCK(alq);
vn_close(alq->aq_vp, FWRITE, alq->aq_cred,
curthread);
crfree(alq->aq_cred);
}
void
alq_destroy(struct alq *alq)
{
/* Drain all pending IO. */
alq_shutdown(alq);
mtx_destroy(&alq->aq_mtx);
free(alq->aq_entbuf, M_ALD);
free(alq, M_ALD);
}
/*
* Flush all pending data to disk. This operation will block.
*/
static int
alq_doio(struct alq *alq)
{
struct thread *td;
struct mount *mp;
struct vnode *vp;
struct uio auio;
struct iovec aiov[2];
int totlen;
int iov;
int vfslocked;
int wrapearly;
KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
vp = alq->aq_vp;
td = curthread;
totlen = 0;
iov = 1;
wrapearly = alq->aq_wrapearly;
bzero(&aiov, sizeof(aiov));
bzero(&auio, sizeof(auio));
/* Start the write from the location of our buffer tail pointer. */
aiov[0].iov_base = alq->aq_entbuf + alq->aq_writetail;
if (alq->aq_writetail < alq->aq_writehead) {
/* Buffer not wrapped. */
totlen = aiov[0].iov_len = alq->aq_writehead - alq->aq_writetail;
} else if (alq->aq_writehead == 0) {
/* Buffer not wrapped (special case to avoid an empty iov). */
totlen = aiov[0].iov_len = alq->aq_buflen - alq->aq_writetail -
wrapearly;
} else {
/*
* Buffer wrapped, requires 2 aiov entries:
* - first is from writetail to end of buffer
* - second is from start of buffer to writehead
*/
aiov[0].iov_len = alq->aq_buflen - alq->aq_writetail -
wrapearly;
iov++;
aiov[1].iov_base = alq->aq_entbuf;
aiov[1].iov_len = alq->aq_writehead;
totlen = aiov[0].iov_len + aiov[1].iov_len;
}
alq->aq_flags |= AQ_FLUSHING;
ALQ_UNLOCK(alq);
auio.uio_iov = &aiov[0];
auio.uio_offset = 0;
auio.uio_segflg = UIO_SYSSPACE;
auio.uio_rw = UIO_WRITE;
auio.uio_iovcnt = iov;
auio.uio_resid = totlen;
auio.uio_td = td;
/*
* Do all of the junk required to write now.
*/
vfslocked = VFS_LOCK_GIANT(vp->v_mount);
vn_start_write(vp, &mp, V_WAIT);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
/*
* XXX: VOP_WRITE error checks are ignored.
*/
#ifdef MAC
if (mac_vnode_check_write(alq->aq_cred, NOCRED, vp) == 0)
#endif
VOP_WRITE(vp, &auio, IO_UNIT | IO_APPEND, alq->aq_cred);
VOP_UNLOCK(vp, 0);
vn_finished_write(mp);
VFS_UNLOCK_GIANT(vfslocked);
ALQ_LOCK(alq);
alq->aq_flags &= ~AQ_FLUSHING;
/* Adjust writetail as required, taking into account wrapping. */
alq->aq_writetail = (alq->aq_writetail + totlen + wrapearly) %
alq->aq_buflen;
alq->aq_freebytes += totlen + wrapearly;
/*
* If we just flushed part of the buffer which wrapped, reset the
* wrapearly indicator.
*/
if (wrapearly)
alq->aq_wrapearly = 0;
/*
* If we just flushed the buffer completely, reset indexes to 0 to
* minimise buffer wraps.
* This is also required to ensure alq_getn() can't wedge itself.
*/
if (!HAS_PENDING_DATA(alq))
alq->aq_writehead = alq->aq_writetail = 0;
KASSERT((alq->aq_writetail >= 0 && alq->aq_writetail < alq->aq_buflen),
("%s: aq_writetail < 0 || aq_writetail >= aq_buflen", __func__));
if (alq->aq_flags & AQ_WANTED) {
alq->aq_flags &= ~AQ_WANTED;
return (1);
}
return(0);
}
static struct kproc_desc ald_kp = {
"ALQ Daemon",
ald_daemon,
&ald_proc
};
SYSINIT(aldthread, SI_SUB_KTHREAD_IDLE, SI_ORDER_ANY, kproc_start, &ald_kp);
SYSINIT(ald, SI_SUB_LOCK, SI_ORDER_ANY, ald_startup, NULL);
/* User visible queue functions */
/*
* Create the queue data structure, allocate the buffer, and open the file.
*/
int
alq_open_flags(struct alq **alqp, const char *file, struct ucred *cred, int cmode,
int size, int flags)
{
struct thread *td;
struct nameidata nd;
struct alq *alq;
int oflags;
int error;
int vfslocked;
KASSERT((size > 0), ("%s: size <= 0", __func__));
*alqp = NULL;
td = curthread;
NDINIT(&nd, LOOKUP, NOFOLLOW | MPSAFE, UIO_SYSSPACE, file, td);
oflags = FWRITE | O_NOFOLLOW | O_CREAT;
error = vn_open_cred(&nd, &oflags, cmode, 0, cred, NULL);
if (error)
return (error);
vfslocked = NDHASGIANT(&nd);
NDFREE(&nd, NDF_ONLY_PNBUF);
/* We just unlock so we hold a reference */
VOP_UNLOCK(nd.ni_vp, 0);
VFS_UNLOCK_GIANT(vfslocked);
alq = malloc(sizeof(*alq), M_ALD, M_WAITOK|M_ZERO);
alq->aq_vp = nd.ni_vp;
alq->aq_cred = crhold(cred);
mtx_init(&alq->aq_mtx, "ALD Queue", NULL, MTX_SPIN|MTX_QUIET);
alq->aq_buflen = size;
alq->aq_entmax = 0;
alq->aq_entlen = 0;
alq->aq_freebytes = alq->aq_buflen;
alq->aq_entbuf = malloc(alq->aq_buflen, M_ALD, M_WAITOK|M_ZERO);
alq->aq_writehead = alq->aq_writetail = 0;
if (flags & ALQ_ORDERED)
alq->aq_flags |= AQ_ORDERED;
if ((error = ald_add(alq)) != 0) {
alq_destroy(alq);
return (error);
}
*alqp = alq;
return (0);
}
int
alq_open(struct alq **alqp, const char *file, struct ucred *cred, int cmode,
int size, int count)
{
int ret;
KASSERT((count >= 0), ("%s: count < 0", __func__));
if (count > 0) {
ret = alq_open_flags(alqp, file, cred, cmode, size*count, 0);
(*alqp)->aq_flags |= AQ_LEGACY;
(*alqp)->aq_entmax = count;
(*alqp)->aq_entlen = size;
} else
ret = alq_open_flags(alqp, file, cred, cmode, size, 0);
return (ret);
}
/*
* Copy a new entry into the queue. If the operation would block either
* wait or return an error depending on the value of waitok.
*/
int
alq_writen(struct alq *alq, void *data, int len, int flags)
{
int activate, copy, ret;
void *waitchan;
KASSERT((len > 0 && len <= alq->aq_buflen),
("%s: len <= 0 || len > aq_buflen", __func__));
activate = ret = 0;
copy = len;
waitchan = NULL;
ALQ_LOCK(alq);
/*
* Fail to perform the write and return EWOULDBLOCK if:
* - The message is larger than our underlying buffer.
* - The ALQ is being shutdown.
* - There is insufficient free space in our underlying buffer
* to accept the message and the user can't wait for space.
* - There is insufficient free space in our underlying buffer
* to accept the message and the alq is inactive due to prior
* use of the ALQ_NOACTIVATE flag (which would lead to deadlock).
*/
if (len > alq->aq_buflen ||
alq->aq_flags & AQ_SHUTDOWN ||
(((flags & ALQ_NOWAIT) || (!(alq->aq_flags & AQ_ACTIVE) &&
HAS_PENDING_DATA(alq))) && alq->aq_freebytes < len)) {
ALQ_UNLOCK(alq);
return (EWOULDBLOCK);
}
/*
* If we want ordered writes and there is already at least one thread
* waiting for resources to become available, sleep until we're woken.
*/
if (alq->aq_flags & AQ_ORDERED && alq->aq_waiters > 0) {
KASSERT(!(flags & ALQ_NOWAIT),
("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
alq->aq_waiters++;
msleep_spin(&alq->aq_waiters, &alq->aq_mtx, "alqwnord", 0);
alq->aq_waiters--;
}
/*
* (ALQ_WAITOK && aq_freebytes < len) or aq_freebytes >= len, either
* enter while loop and sleep until we have enough free bytes (former)
* or skip (latter). If AQ_ORDERED is set, only 1 thread at a time will
* be in this loop. Otherwise, multiple threads may be sleeping here
* competing for ALQ resources.
*/
while (alq->aq_freebytes < len && !(alq->aq_flags & AQ_SHUTDOWN)) {
KASSERT(!(flags & ALQ_NOWAIT),
("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
alq->aq_flags |= AQ_WANTED;
alq->aq_waiters++;
if (waitchan)
wakeup(waitchan);
msleep_spin(alq, &alq->aq_mtx, "alqwnres", 0);
alq->aq_waiters--;
/*
* If we're the first thread to wake after an AQ_WANTED wakeup
* but there isn't enough free space for us, we're going to loop
* and sleep again. If there are other threads waiting in this
* loop, schedule a wakeup so that they can see if the space
* they require is available.
*/
if (alq->aq_waiters > 0 && !(alq->aq_flags & AQ_ORDERED) &&
alq->aq_freebytes < len && !(alq->aq_flags & AQ_WANTED))
waitchan = alq;
else
waitchan = NULL;
}
/*
* If there are waiters, we need to signal the waiting threads after we
* complete our work. The alq ptr is used as a wait channel for threads
* requiring resources to be freed up. In the AQ_ORDERED case, threads
* are not allowed to concurrently compete for resources in the above
* while loop, so we use a different wait channel in this case.
*/
if (alq->aq_waiters > 0) {
if (alq->aq_flags & AQ_ORDERED)
waitchan = &alq->aq_waiters;
else
waitchan = alq;
} else
waitchan = NULL;
/* Bail if we're shutting down. */
if (alq->aq_flags & AQ_SHUTDOWN) {
ret = EWOULDBLOCK;
goto unlock;
}
/*
* If we need to wrap the buffer to accommodate the write,
* we'll need 2 calls to bcopy.
*/
if ((alq->aq_buflen - alq->aq_writehead) < len)
copy = alq->aq_buflen - alq->aq_writehead;
/* Copy message (or part thereof if wrap required) to the buffer. */
bcopy(data, alq->aq_entbuf + alq->aq_writehead, copy);
alq->aq_writehead += copy;
if (alq->aq_writehead >= alq->aq_buflen) {
KASSERT((alq->aq_writehead == alq->aq_buflen),
("%s: alq->aq_writehead (%d) > alq->aq_buflen (%d)",
__func__,
alq->aq_writehead,
alq->aq_buflen));
alq->aq_writehead = 0;
}
if (copy != len) {
/*
* Wrap the buffer by copying the remainder of our message
* to the start of the buffer and resetting aq_writehead.
*/
bcopy(((uint8_t *)data)+copy, alq->aq_entbuf, len - copy);
alq->aq_writehead = len - copy;
}
KASSERT((alq->aq_writehead >= 0 && alq->aq_writehead < alq->aq_buflen),
("%s: aq_writehead < 0 || aq_writehead >= aq_buflen", __func__));
alq->aq_freebytes -= len;
if (!(alq->aq_flags & AQ_ACTIVE) && !(flags & ALQ_NOACTIVATE)) {
alq->aq_flags |= AQ_ACTIVE;
activate = 1;
}
KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
unlock:
ALQ_UNLOCK(alq);
if (activate) {
ALD_LOCK();
ald_activate(alq);
ALD_UNLOCK();
}
/* NB: We rely on wakeup_one waking threads in a FIFO manner. */
if (waitchan != NULL)
wakeup_one(waitchan);
return (ret);
}
int
alq_write(struct alq *alq, void *data, int flags)
{
/* Should only be called in fixed length message (legacy) mode. */
KASSERT((alq->aq_flags & AQ_LEGACY),
("%s: fixed length write on variable length queue", __func__));
return (alq_writen(alq, data, alq->aq_entlen, flags));
}
/*
* Retrieve a pointer for the ALQ to write directly into, avoiding bcopy.
*/
struct ale *
alq_getn(struct alq *alq, int len, int flags)
{
int contigbytes;
void *waitchan;
KASSERT((len > 0 && len <= alq->aq_buflen),
("%s: len <= 0 || len > alq->aq_buflen", __func__));
waitchan = NULL;
ALQ_LOCK(alq);
/*
* Determine the number of free contiguous bytes.
* We ensure elsewhere that if aq_writehead == aq_writetail because
* the buffer is empty, they will both be set to 0 and therefore
* aq_freebytes == aq_buflen and is fully contiguous.
* If they are equal and the buffer is not empty, aq_freebytes will
* be 0 indicating the buffer is full.
*/
if (alq->aq_writehead <= alq->aq_writetail)
contigbytes = alq->aq_freebytes;
else {
contigbytes = alq->aq_buflen - alq->aq_writehead;
if (contigbytes < len) {
/*
* Insufficient space at end of buffer to handle a
* contiguous write. Wrap early if there's space at
* the beginning. This will leave a hole at the end
* of the buffer which we will have to skip over when
* flushing the buffer to disk.
*/
if (alq->aq_writetail >= len || flags & ALQ_WAITOK) {
/* Keep track of # bytes left blank. */
alq->aq_wrapearly = contigbytes;
/* Do the wrap and adjust counters. */
contigbytes = alq->aq_freebytes =
alq->aq_writetail;
alq->aq_writehead = 0;
}
}
}
/*
* Return a NULL ALE if:
* - The message is larger than our underlying buffer.
* - The ALQ is being shutdown.
* - There is insufficient free space in our underlying buffer
* to accept the message and the user can't wait for space.
* - There is insufficient free space in our underlying buffer
* to accept the message and the alq is inactive due to prior
* use of the ALQ_NOACTIVATE flag (which would lead to deadlock).
*/
if (len > alq->aq_buflen ||
alq->aq_flags & AQ_SHUTDOWN ||
(((flags & ALQ_NOWAIT) || (!(alq->aq_flags & AQ_ACTIVE) &&
HAS_PENDING_DATA(alq))) && contigbytes < len)) {
ALQ_UNLOCK(alq);
return (NULL);
}
/*
* If we want ordered writes and there is already at least one thread
* waiting for resources to become available, sleep until we're woken.
*/
if (alq->aq_flags & AQ_ORDERED && alq->aq_waiters > 0) {
KASSERT(!(flags & ALQ_NOWAIT),
("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
alq->aq_waiters++;
msleep_spin(&alq->aq_waiters, &alq->aq_mtx, "alqgnord", 0);
alq->aq_waiters--;
}
/*
* (ALQ_WAITOK && contigbytes < len) or contigbytes >= len, either enter
* while loop and sleep until we have enough contiguous free bytes
* (former) or skip (latter). If AQ_ORDERED is set, only 1 thread at a
* time will be in this loop. Otherwise, multiple threads may be
* sleeping here competing for ALQ resources.
*/
while (contigbytes < len && !(alq->aq_flags & AQ_SHUTDOWN)) {
KASSERT(!(flags & ALQ_NOWAIT),
("%s: ALQ_NOWAIT set but incorrectly ignored!", __func__));
alq->aq_flags |= AQ_WANTED;
alq->aq_waiters++;
if (waitchan)
wakeup(waitchan);
msleep_spin(alq, &alq->aq_mtx, "alqgnres", 0);
alq->aq_waiters--;
if (alq->aq_writehead <= alq->aq_writetail)
contigbytes = alq->aq_freebytes;
else
contigbytes = alq->aq_buflen - alq->aq_writehead;
/*
* If we're the first thread to wake after an AQ_WANTED wakeup
* but there isn't enough free space for us, we're going to loop
* and sleep again. If there are other threads waiting in this
* loop, schedule a wakeup so that they can see if the space
* they require is available.
*/
if (alq->aq_waiters > 0 && !(alq->aq_flags & AQ_ORDERED) &&
contigbytes < len && !(alq->aq_flags & AQ_WANTED))
waitchan = alq;
else
waitchan = NULL;
}
/*
* If there are waiters, we need to signal the waiting threads after we
* complete our work. The alq ptr is used as a wait channel for threads
* requiring resources to be freed up. In the AQ_ORDERED case, threads
* are not allowed to concurrently compete for resources in the above
* while loop, so we use a different wait channel in this case.
*/
if (alq->aq_waiters > 0) {
if (alq->aq_flags & AQ_ORDERED)
waitchan = &alq->aq_waiters;
else
waitchan = alq;
} else
waitchan = NULL;
/* Bail if we're shutting down. */
if (alq->aq_flags & AQ_SHUTDOWN) {
ALQ_UNLOCK(alq);
if (waitchan != NULL)
wakeup_one(waitchan);
return (NULL);
}
/*
* If we are here, we have a contiguous number of bytes >= len
* available in our buffer starting at aq_writehead.
*/
alq->aq_getpost.ae_data = alq->aq_entbuf + alq->aq_writehead;
alq->aq_getpost.ae_bytesused = len;
return (&alq->aq_getpost);
}
struct ale *
alq_get(struct alq *alq, int flags)
{
/* Should only be called in fixed length message (legacy) mode. */
KASSERT((alq->aq_flags & AQ_LEGACY),
("%s: fixed length get on variable length queue", __func__));
return (alq_getn(alq, alq->aq_entlen, flags));
}
void
alq_post_flags(struct alq *alq, struct ale *ale, int flags)
{
int activate;
void *waitchan;
activate = 0;
if (ale->ae_bytesused > 0) {
if (!(alq->aq_flags & AQ_ACTIVE) &&
!(flags & ALQ_NOACTIVATE)) {
alq->aq_flags |= AQ_ACTIVE;
activate = 1;
}
alq->aq_writehead += ale->ae_bytesused;
alq->aq_freebytes -= ale->ae_bytesused;
/* Wrap aq_writehead if we filled to the end of the buffer. */
if (alq->aq_writehead == alq->aq_buflen)
alq->aq_writehead = 0;
KASSERT((alq->aq_writehead >= 0 &&
alq->aq_writehead < alq->aq_buflen),
("%s: aq_writehead < 0 || aq_writehead >= aq_buflen",
__func__));
KASSERT((HAS_PENDING_DATA(alq)), ("%s: queue empty!", __func__));
}
/*
* If there are waiters, we need to signal the waiting threads after we
* complete our work. The alq ptr is used as a wait channel for threads
* requiring resources to be freed up. In the AQ_ORDERED case, threads
* are not allowed to concurrently compete for resources in the
* alq_getn() while loop, so we use a different wait channel in this case.
*/
if (alq->aq_waiters > 0) {
if (alq->aq_flags & AQ_ORDERED)
waitchan = &alq->aq_waiters;
else
waitchan = alq;
} else
waitchan = NULL;
ALQ_UNLOCK(alq);
if (activate) {
ALD_LOCK();
ald_activate(alq);
ALD_UNLOCK();
}
/* NB: We rely on wakeup_one waking threads in a FIFO manner. */
if (waitchan != NULL)
wakeup_one(waitchan);
}
void
alq_flush(struct alq *alq)
{
int needwakeup = 0;
ALD_LOCK();
ALQ_LOCK(alq);
/*
* Pull the lever iff there is data to flush and we're
* not already in the middle of a flush operation.
*/
if (HAS_PENDING_DATA(alq) && !(alq->aq_flags & AQ_FLUSHING)) {
if (alq->aq_flags & AQ_ACTIVE)
ald_deactivate(alq);
ALD_UNLOCK();
needwakeup = alq_doio(alq);
} else
ALD_UNLOCK();
ALQ_UNLOCK(alq);
if (needwakeup)
wakeup_one(alq);
}
/*
* Flush remaining data, close the file and free all resources.
*/
void
alq_close(struct alq *alq)
{
/* Only flush and destroy alq if not already shutting down. */
if (ald_rem(alq) == 0)
alq_destroy(alq);
}
static int
alq_load_handler(module_t mod, int what, void *arg)
{
int ret;
ret = 0;
switch (what) {
case MOD_LOAD:
case MOD_SHUTDOWN:
break;
case MOD_QUIESCE:
ALD_LOCK();
/* Only allow unload if there are no open queues. */
if (LIST_FIRST(&ald_queues) == NULL) {
ald_shutingdown = 1;
ALD_UNLOCK();
ald_shutdown(NULL, 0);
mtx_destroy(&ald_mtx);
} else {
ALD_UNLOCK();
ret = EBUSY;
}
break;
case MOD_UNLOAD:
/* If MOD_QUIESCE failed we must fail here too. */
if (ald_shutingdown == 0)
ret = EBUSY;
break;
default:
ret = EINVAL;
break;
}
return (ret);
}
static moduledata_t alq_mod =
{
"alq",
alq_load_handler,
NULL
};
DECLARE_MODULE(alq, alq_mod, SI_SUB_SMP, SI_ORDER_ANY);
MODULE_VERSION(alq, 1);