From: "Jeff V. Merkey" <jmerkey@wolfmountaingroup.com>
To: Joshua Hudson <joshudson@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: readers-writers mutex
Date: Wed, 05 Apr 2006 19:15:17 -0600 [thread overview]
Message-ID: <44346BA5.7060400@wolfmountaingroup.com> (raw)
In-Reply-To: <bda6d13a0604051521o229de77dvb38992d6427a450c@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2468 bytes --]
Joshua Hudson wrote:
>Since we are moving from semaphores to mutex, there should be a
>mutex_rw. I had a try
>at creating one (might as well convert from sem_rw). I'll bet somebody
>here can do a
>lot better, but this will do if need be.
>
>--- linux-2.6.16.1-stock/include/linux/mutex_rw.h 1969-12-31
>16:00:00.000000000 -0800
>+++ linux-2.6.16.1-nvl/include/linux/mutex_rw.h 2006-04-04
>18:11:56.000000000 -0700
>@@ -0,0 +1,60 @@
>+/* Linux RW mutex
>+ * This file: GNU GPL v2 or later, Joshua Hudson <joshudson@gmail.com>
>+ *
>+ * Somebody else can make this fast. I just made this work.
>+ *
>+ * DANGER! Change of this file will break module binaries if any
>+ * rw mutex is shared between main kernel and modules or between
>+ * modules with a different version.
>+ */
>+
>+#ifndef __KERNEL_MUTEX_RW
>+#define __KERNEL_MUTEX_RW
>+#ifdef __KERNEL__
>+
>+#include <linux/mutex.h>
>+
>+struct rw_mutex {
>+ struct mutex r_mutex;
>+ struct mutex w_mutex;
>+ unsigned n_readers;
>+};
>+
>+static inline void rw_mutex_init(struct rw_mutex *rw)
>+{
>+ mutex_init(&rw->r_mutex);
>+ mutex_init(&rw->w_mutex);
>+ rw->n_readers = 0;
>+}
>+
>+static inline void rw_mutex_destroy(struct rw_mutex *rw)
>+{
>+ mutex_destroy(&rw->r_mutex);
>+ mutex_destroy(&rw->w_mutex);
>+}
>+
>+static inline void mutex_lock_w(struct rw_mutex *rw)
>+{
>+ mutex_lock(&rw->w_mutex);
>+}
>+
>+static inline void mutex_unlock_w(struct rw_mutex *rw)
>+{
>+ mutex_unlock(&rw->w_mutex);
>+}
>+
>+static inline void mutex_lock_r(struct rw_mutex *rw)
>+{
>+ mutex_lock(&rw->r_mutex);
>+ if (++rw->n_readers == 1)
>+ mutex_lock(&rw->w_mutex);
>+ mutex_unlock(&rw->r_mutex);
>+}
>+
>+static inline void mutex_unlock_r(struct rw_mutex *rw)
>+{
>+ mutex_lock(&rw->r_mutex);
>+ if (--rw->n_readers == 0)
>+ mutex_unlock(&rw->w_mutex);
>+ mutex_unlock(&rw->r_mutex);
>+}
>+
>+#endif
>+#endif
>-
>To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at http://vger.kernel.org/majordomo-info.html
>Please read the FAQ at http://www.tux.org/lkml/
>
>
>
Race conditions here.
Try this code. These have been tested and I have been using the code for
couple of years in another OS (which is just about done now and is in
alpha and beta and little more SMP friendly).
Jeff
[-- Attachment #2: rwlock.c --]
[-- Type: text/x-csrc, Size: 22909 bytes --]
/***************************************************************************
*
* Copyright (c) 2005, 2006 Cherokee Nation. All Rights Reserved.
*
* This Program is released under GPLv3
*
* AUTHOR : Jeff V. Merkey
* FILE : RWLOCK.C
* DESCRIP : Multi-Processing Reader/Writer Locks Gadugi v7
* DATE : October 23, 2004
*
***************************************************************************/
#include "stdarg.h"
#include "stdio.h"
#include "stdlib.h"
#include "ctype.h"
#include "string.h"
#include "kernel.h"
#include "keyboard.h"
#include "screen.h"
#include "types.h"
#include "emit.h"
#include "dos.h"
#include "tss.h"
#include "os.h"
#include "mps.h"
#include "hal.h"
#include "timer.h"
#include "peexe.h"
#include "malloc.h"
#include "free.h"
#include "event.h"
#define WRITER_OWNED -10
#define READER_OWNED -11
#define UNOWNED -12
rwlock_t *rwlock_init(rwlock_t *rwlock);
rwlock_t *rwlock_alloc(void);
LONG rwlock_free(rwlock_t *rwlock);
LONG rwlock_read_lock(rwlock_t *rwlock);
LONG rwlock_write_lock(rwlock_t *rwlock);
LONG rwlock_read_try_lock(rwlock_t *rwlock);
LONG rwlock_write_try_lock(rwlock_t *rwlock);
LONG rwlock_unlock(rwlock_t *rwlock);
LONG rwlock_reader_to_writer(rwlock_t *rwlock);
LONG rwlock_reader_to_writer_unordered(rwlock_t *rwlock);
LONG rwlock_writer_to_reader(rwlock_t *rwlock);
LONG rwlock_release(rwlock_t *rwlock);
PROCESS *get_rwlock_process(rwlock_t *rwlock);
void put_rwlock_process(rwlock_t *rwlock, PROCESS *p);
rwlock_t *rwlock_init(rwlock_t *rwlock)
{
if (rwlock && !rwlock->signature)
{
SetData((LONG *) rwlock, 0, sizeof(rwlock_t));
rwlock->signature = LRWLOCK_SIGNATURE;
rwlock->flags = UNOWNED;
return (rwlock_t *) rwlock;
}
return 0;
}
rwlock_t *rwlock_alloc(void)
{
register rwlock_t *rwlock;
rwlock = kmalloc(sizeof(rwlock_t));
if (rwlock)
{
SetData((LONG *) rwlock, 0, sizeof(rwlock_t));
rwlock->signature = RWLOCK_SIGNATURE;
rwlock->flags = UNOWNED;
return (rwlock_t *) rwlock;
}
return 0;
}
LONG rwlock_free(rwlock_t *rwlock)
{
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
if (!rwlock_release(rwlock))
{
if (rwlock->signature == RWLOCK_SIGNATURE)
kfree(rwlock);
else
rwlock->signature = 0;
return 0;
}
return -2;
}
return -1;
}
#if RWLOCK_TRACE
BYTE *get_RW_TYPE(LONG p)
{
switch (p)
{
case RREAD_LOCK:
return "READ_LOCK";
case RREAD_UNLOCK:
return "READ_UNLOCK";
case WWRITE_LOCK:
return "WRITE_LOCK";
case WWRITE_UNLOCK:
return "WRITE_UNLOCK";
default:
return "????";
}
}
BYTE *get_RW_OP(LONG p)
{
switch (p)
{
case READER_LOCK:
return "READER_LOCK ";
case READER_UNLOCK:
return "READER_UNLOCK";
case READER_SLEEP:
return "READER_SLEEP ";
case READER_WAKE:
return "READER_WAKE ";
case WRITER_LOCK:
return "WRITER_LOCK ";
case WRITER_UNLOCK:
return "WRITER_UNLOCK";
case WRITER_SLEEP:
return "WRITER_SLEEP ";
case WRITER_WAKE:
return "WRITER_WAKE ";
default:
return "???? ";
}
}
void RW_DISPLAY(SCREEN *screen, rwlock_t *rwlock)
{
register LONG i;
SetPauseMode(screen, screen->nLines - 5);
printfScreen(screen, "RWIndex %d\n");
for (i=0; i < 256; i++)
{
printfScreen(screen, "process-%08X time-%08X target-%08X s-%s t-%s\n",
rwlock->RWProcess[i],
rwlock->RWTime[i],
rwlock->RWTarget[i],
get_RW_OP(rwlock->RWOp[i]),
get_RW_TYPE(rwlock->RWType[i]));
}
ClearPauseMode(screen);
return;
}
void RW_TRACE(rwlock_t *rwlock, LONG event, LONG target, LONG type)
{
LONG base, counter;
GetSystemDTSC(&base, &counter);
rwlock->RWProcess[rwlock->RWIndex & 0xFF] = (LONG) get_running_process();
rwlock->RWOp[rwlock->RWIndex & 0xFF] = event;
rwlock->RWTarget[rwlock->RWIndex & 0xFF] = target;
rwlock->RWType[rwlock->RWIndex & 0xFF] = type;
rwlock->RWTime[rwlock->RWIndex & 0xFF] = (LONG) base;
rwlock->RWIndex++;
}
#endif
LONG rwlock_read_lock(rwlock_t *rwlock)
{
register PROCESS *p = get_running_process();
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
p->syncFlag = 0;
switch (rwlock->flags)
{
case WRITER_OWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_SLEEP, (LONG) p, RREAD_LOCK);
#endif
spin_lock(&p->threadMutex); // lock current thread
put_rwlock_process(rwlock, p);
p->stackPointer = 0;
p->threadState = PS_SLEEP;
p->syncObject = rwlock;
p->syncState = PROCESS_READER_BLOCKED_SYNC;
spin_unlock(&rwlock->mutex);
thread_switch(); // context switch will unlock thread
cli();
set_flags(flags);
return p->syncFlag;
case READER_OWNED:
if (rwlock->writers)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_SLEEP, (LONG) p, RREAD_LOCK);
#endif
spin_lock(&p->threadMutex); // lock current thread
put_rwlock_process(rwlock, p);
p->stackPointer = 0;
p->threadState = PS_SLEEP;
p->syncObject = rwlock;
p->syncState = PROCESS_READER_BLOCKED_SYNC;
spin_unlock(&rwlock->mutex);
thread_switch(); // context switch will unlock thread
cli();
set_flags(flags);
return p->syncFlag;
}
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, RREAD_LOCK);
#endif
rwlock->flags = (LONG) READER_OWNED;
rwlock->readers++; // set reader count
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
case UNOWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, RREAD_LOCK);
#endif
rwlock->flags = (LONG) READER_OWNED;
rwlock->readers++; // set reader count
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
default:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_write_lock(rwlock_t *rwlock)
{
register PROCESS *p = get_running_process();
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
p->syncFlag = 0;
switch (rwlock->flags)
{
case READER_OWNED:
case WRITER_OWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_SLEEP, (LONG) p, WWRITE_LOCK);
#endif
spin_lock(&p->threadMutex); // lock current thread
put_rwlock_process(rwlock, p);
rwlock->writers++;
p->stackPointer = 0;
p->threadState = PS_SLEEP;
p->syncObject = rwlock;
p->syncState = PROCESS_WRITER_BLOCKED_SYNC;
spin_unlock(&rwlock->mutex);
thread_switch(); // context switch will unlock thread
cli();
set_flags(flags);
return p->syncFlag;
case UNOWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, WWRITE_LOCK);
#endif
rwlock->flags = (LONG) WRITER_OWNED;
rwlock->owner = (LONG) p;
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
default:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_read_try_lock(rwlock_t *rwlock)
{
register PROCESS *p = get_running_process();
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
p->syncFlag = 0;
switch (rwlock->flags)
{
case WRITER_OWNED:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 1;
case READER_OWNED:
if (rwlock->writers)
{
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 1;
}
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, RREAD_TRY_LOCK);
#endif
rwlock->flags = (LONG) READER_OWNED;
rwlock->readers++; // set reader count
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
case UNOWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, RREAD_TRY_LOCK);
#endif
rwlock->flags = (LONG) READER_OWNED;
rwlock->readers++; // set reader count
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
default:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_write_try_lock(rwlock_t *rwlock)
{
register PROCESS *p = get_running_process();
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
p->syncFlag = 0;
switch (rwlock->flags)
{
case READER_OWNED:
case WRITER_OWNED:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 1;
case UNOWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, WWRITE_TRY_LOCK);
#endif
rwlock->flags = (LONG) WRITER_OWNED;
rwlock->owner = (LONG) p;
spin_unlock(&rwlock->mutex);
set_flags(flags);
return p->syncFlag;
default:
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_read_unlock(rwlock_t *rwlock)
{
register PROCESS *p;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
switch (rwlock->flags)
{
case WRITER_OWNED:
panic("rwlock_read_unlock called with writer owning rwlock");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
case READER_OWNED:
if (rwlock->readers)
rwlock->readers--;
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_UNLOCK, 0, RREAD_UNLOCK);
#endif
if (!rwlock->readers)
{
rwlock->flags = UNOWNED;
if (rwlock->head)
{
p = rwlock->head;
if (p->syncState != PROCESS_WRITER_BLOCKED_SYNC)
{
panic("rwlock_read_unlock called with sleeping READER");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
p = get_rwlock_process(rwlock);
rwlock->writers--;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_WAKE, (LONG) p, RREAD_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, RREAD_UNLOCK);
#endif
rwlock->flags = WRITER_OWNED;
rwlock->owner = (LONG) p;
}
spin_unlock(&p->threadMutex); // unlock thread
}
}
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
case UNOWNED:
default:
panic("rwlock_read_unlock called in inconsistent state");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_write_unlock(rwlock_t *rwlock)
{
register PROCESS *p, *curr;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
curr = get_running_process();
if (rwlock->owner != (LONG) curr)
{
panic("rwlock_write_unlock called by process other than owner");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
switch (rwlock->flags)
{
case WRITER_OWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_UNLOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->owner = 0;
rwlock->flags = UNOWNED;
if (rwlock->head)
{
p = rwlock->head;
if (p->syncState == PROCESS_WRITER_BLOCKED_SYNC)
{
p = get_rwlock_process(rwlock);
rwlock->writers--;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_WAKE, (LONG) p, WWRITE_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->flags = WRITER_OWNED;
rwlock->owner = (LONG) p;
}
spin_unlock(&p->threadMutex); // unlock thread
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
}
while (rwlock->head)
{
p = rwlock->head;
if (p->syncState == PROCESS_WRITER_BLOCKED_SYNC)
break;
p = get_rwlock_process(rwlock);
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_WAKE, (LONG) p, WWRITE_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->flags = READER_OWNED;
rwlock->readers++;
rwlock->owner = 0; }
}
spin_unlock(&p->threadMutex); // unlock thread
}
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
case READER_OWNED:
panic("rwlock_write_unlock called with reader owning rwlock");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
case UNOWNED:
default:
panic("rwlock_write_unlock called in inconsistent state");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_reader_to_writer(rwlock_t *rwlock)
{
register PROCESS *p;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
switch (rwlock->flags)
{
case WRITER_OWNED:
panic("rwlock_reader_to_writer called with writer owning rwlock");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
case READER_OWNED:
if (rwlock->readers)
rwlock->readers--;
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_UNLOCK, 0, RREAD_UNLOCK);
#endif
if (!rwlock->readers)
{
rwlock->flags = UNOWNED;
if (rwlock->head)
{
p = rwlock->head;
if (p->syncState != PROCESS_WRITER_BLOCKED_SYNC)
{
panic("rwlock_read_unlock called with sleeping READER");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
p = get_rwlock_process(rwlock);
rwlock->writers--;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_WAKE, (LONG) p, RREAD_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, RREAD_UNLOCK);
#endif
rwlock->flags = WRITER_OWNED;
rwlock->owner = (LONG) p;
}
spin_unlock(&p->threadMutex); // unlock thread
}
}
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
case UNOWNED:
default:
panic("rwlock_reader_to_writer called in inconsistent state");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_reader_to_writer_unordered(rwlock_t *rwlock)
{
register PROCESS *p;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
switch (rwlock->flags)
{
case WRITER_OWNED:
panic("rwlock_reader_to_writer_unordered called with writer owning rwlock");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
case READER_OWNED:
if (rwlock->readers)
rwlock->readers--;
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_UNLOCK, 0, RREAD_UNLOCK);
#endif
if (!rwlock->readers)
{
rwlock->flags = UNOWNED;
if (rwlock->head)
{
p = rwlock->head;
if (p->syncState != PROCESS_WRITER_BLOCKED_SYNC)
{
panic("rwlock_read_unlock called with sleeping READER");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
p = get_rwlock_process(rwlock);
rwlock->writers--;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_WAKE, (LONG) p, RREAD_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, RREAD_UNLOCK);
#endif
rwlock->flags = WRITER_OWNED;
rwlock->owner = (LONG) p;
}
spin_unlock(&p->threadMutex); // unlock thread
}
}
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
case UNOWNED:
default:
panic("rwlock_reader_to_writer_unordered called in inconsistent state");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
LONG rwlock_writer_to_reader(rwlock_t *rwlock)
{
register PROCESS *p, *curr;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
curr = get_running_process();
if (rwlock->owner != (LONG) curr)
{
panic("rwlock_writer_to_reader called by process other than owner");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
switch (rwlock->flags)
{
case WRITER_OWNED:
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_UNLOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->owner = 0;
rwlock->flags = UNOWNED;
if (rwlock->head)
{
p = rwlock->head;
if (p->syncState == PROCESS_WRITER_BLOCKED_SYNC)
{
p = get_rwlock_process(rwlock);
rwlock->writers--;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_WAKE, (LONG) p, WWRITE_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, WRITER_LOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->flags = WRITER_OWNED;
rwlock->owner = (LONG) p;
}
spin_unlock(&p->threadMutex); // unlock thread
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
}
while (rwlock->head)
{
p = rwlock->head;
if (p->syncState == PROCESS_WRITER_BLOCKED_SYNC)
break;
p = get_rwlock_process(rwlock);
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_WAKE, (LONG) p, WWRITE_UNLOCK);
#endif
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = 0;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
#if RWLOCK_TRACE
RW_TRACE(rwlock, READER_LOCK, 0, WWRITE_UNLOCK);
#endif
rwlock->flags = READER_OWNED;
rwlock->readers++;
rwlock->owner = 0; }
}
spin_unlock(&p->threadMutex); // unlock thread
}
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
case READER_OWNED:
panic("rwlock_writer_to_reader called with reader owning rwlock");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
case UNOWNED:
default:
panic("rwlock_writer_to_reader called in inconsistent state");
spin_unlock(&rwlock->mutex);
set_flags(flags);
return -1;
}
}
return -1;
}
PROCESS *get_rwlock_process(rwlock_t *rwlock)
{
register PROCESS *p, *list;
if (rwlock->head)
{
p = rwlock->head;
list = (PROCESS *) rwlock->head = (void *) p->syncNext;
if (list)
list->syncPrior = NULL;
else
rwlock->tail = NULL;
return p;
}
return 0;
}
void put_rwlock_process(rwlock_t *rwlock, PROCESS *p)
{
register PROCESS *search, *list;
search = rwlock->head;
while (search)
{
if (search == p)
return;
search = search->syncNext;
}
if (!rwlock->head)
{
rwlock->head = rwlock->tail = p;
p->syncNext = p->syncPrior = 0;
}
else
{
list = (PROCESS *) rwlock->tail;
list->syncNext = p;
p->syncNext = 0;
p->syncPrior = rwlock->tail;
rwlock->tail = p;
}
return;
}
LONG rwlock_release(rwlock_t *rwlock)
{
register PROCESS *p, *list;
register LONG flags;
if (rwlock->signature == RWLOCK_SIGNATURE ||
rwlock->signature == LRWLOCK_SIGNATURE)
{
flags = get_flags();
spin_lock(&rwlock->mutex);
p = rwlock->head;
while (p)
{
list = p->syncNext;
spin_lock(&p->threadMutex); // lock thread
if (p->threadState == PS_SLEEP)
{
p->threadState = PS_ACTIVE;
p->syncObject = 0;
p->syncState = 0;
p->syncFlag = -2;
if (rwlock->waiters)
rwlock->waiters--;
(!p->processorBinding)
? put_dispatch(p)
: put_bind_pset(p, (PROCESSOR_SET *)p->processorBinding);
}
spin_unlock(&p->threadMutex); // unlock thread
p = list;
}
rwlock->owner = 0;
spin_unlock(&rwlock->mutex);
set_flags(flags);
return 0;
}
return -1;
}
prev parent reply other threads:[~2006-04-06 0:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-05 22:21 readers-writers mutex Joshua Hudson
2006-04-06 1:06 ` Arjan van de Ven
2006-04-06 1:59 ` Joshua Hudson
2006-04-06 1:15 ` Jeff V. Merkey [this message]
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