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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
Attached is a test program that uses the nspr1 to demonstrate a bug
under NT4.0. The fix has already been mentioned (add a ResetEvent just
before leaving the critical section in _PR_CondWait in hwmon.c).
*/
#include "prthread.h"
#include "prtypes.h"
#include "prinit.h"
#include "prmon.h"
#include "prlog.h"
typedef struct Arg_s
{
PRInt32 a, b;
} Arg_t;
PRMonitor* gMonitor; // the monitor
PRInt32 gReading; // number of read locks
PRInt32 gWriteWaiting; // number of threads waiting for write lock
PRInt32 gReadWaiting; // number of threads waiting for read lock
PRInt32 gCounter; // a counter
// stats
PRInt32 gReads; // number of successful reads
PRInt32 gMaxReads; // max number of simultaneous reads
PRInt32 gMaxWriteWaits; // max number of writes that waited for read
PRInt32 gMaxReadWaits; // max number of reads that waited for write wait
void spin (PRInt32 aDelay)
{
PRInt32 index;
PRInt32 delay = aDelay * 1000;
PR_Sleep(0);
// randomize delay a bit
delay = (delay / 2) + (PRInt32)((float)delay *
((float)rand () / (float)RAND_MAX));
for (index = 0; index < delay * 10; index++)
// consume a bunch of cpu cycles
;
PR_Sleep(0);
}
void doWriteThread (void* arg)
{
PRInt32 last;
Arg_t *args = (Arg_t*)arg;
PRInt32 aWorkDelay = args->a, aWaitDelay = args->b;
PR_Sleep(0);
while (1)
{
// -- enter write lock
PR_EnterMonitor (gMonitor);
if (0 < gReading) // wait for read locks to go away
{
PRIntervalTime fiveSecs = PR_SecondsToInterval(5);
gWriteWaiting++;
if (gWriteWaiting > gMaxWriteWaits) // stats
gMaxWriteWaits = gWriteWaiting;
while (0 < gReading)
PR_Wait (gMonitor, fiveSecs);
gWriteWaiting--;
}
// -- write lock entered
last = gCounter;
gCounter++;
spin (aWorkDelay);
PR_ASSERT (gCounter == (last + 1)); // test invariance
// -- exit write lock
// if (0 < gReadWaiting) // notify waiting reads (do it anyway to show off the CondWait bug)
PR_NotifyAll (gMonitor);
PR_ExitMonitor (gMonitor);
// -- write lock exited
spin (aWaitDelay);
}
}
void doReadThread (void* arg)
{
PRInt32 last;
Arg_t *args = (Arg_t*)arg;
PRInt32 aWorkDelay = args->a, aWaitDelay = args->b;
PR_Sleep(0);
while (1)
{
// -- enter read lock
PR_EnterMonitor (gMonitor);
if (0 < gWriteWaiting) // give up the monitor to waiting writes
{
PRIntervalTime fiveSecs = PR_SecondsToInterval(5);
gReadWaiting++;
if (gReadWaiting > gMaxReadWaits) // stats
gMaxReadWaits = gReadWaiting;
while (0 < gWriteWaiting)
PR_Wait (gMonitor, fiveSecs);
gReadWaiting--;
}
gReading++;
gReads++; // stats
if (gReading > gMaxReads) // stats
gMaxReads = gReading;
PR_ExitMonitor (gMonitor);
// -- read lock entered
last = gCounter;
spin (aWorkDelay);
PR_ASSERT (gCounter == last); // test invariance
// -- exit read lock
PR_EnterMonitor (gMonitor); // read unlock
gReading--;
// if ((0 == gReading) && (0 < gWriteWaiting)) // notify waiting writes (do it anyway to show off the CondWait bug)
PR_NotifyAll (gMonitor);
PR_ExitMonitor (gMonitor);
// -- read lock exited
spin (aWaitDelay);
}
}
void fireThread (
char* aName, void (*aProc)(void *arg), Arg_t *aArg)
{
PRThread *thread = PR_CreateThread(
PR_USER_THREAD, aProc, aArg, PR_PRIORITY_NORMAL,
PR_LOCAL_THREAD, PR_UNJOINABLE_THREAD, 0);
}
int pseudoMain (int argc, char** argv, char *pad)
{
PRInt32 lastWriteCount = gCounter;
PRInt32 lastReadCount = gReads;
Arg_t a1 = {500, 250};
Arg_t a2 = {500, 500};
Arg_t a3 = {250, 500};
Arg_t a4 = {750, 250};
Arg_t a5 = {100, 750};
Arg_t a6 = {100, 500};
Arg_t a7 = {100, 750};
gMonitor = PR_NewMonitor ();
fireThread ("R1", doReadThread, &a1);
fireThread ("R2", doReadThread, &a2);
fireThread ("R3", doReadThread, &a3);
fireThread ("R4", doReadThread, &a4);
fireThread ("W1", doWriteThread, &a5);
fireThread ("W2", doWriteThread, &a6);
fireThread ("W3", doWriteThread, &a7);
fireThread ("R5", doReadThread, &a1);
fireThread ("R6", doReadThread, &a2);
fireThread ("R7", doReadThread, &a3);
fireThread ("R8", doReadThread, &a4);
fireThread ("W4", doWriteThread, &a5);
fireThread ("W5", doWriteThread, &a6);
fireThread ("W6", doWriteThread, &a7);
while (1)
{
PRInt32 writeCount, readCount;
PRIntervalTime fiveSecs = PR_SecondsToInterval(5);
PR_Sleep (fiveSecs); // get out of the way
// print some stats, not threadsafe, informative only
writeCount = gCounter;
readCount = gReads;
printf ("\ntick %d writes (+%d), %d reads (+%d) [max %d, %d, %d]",
writeCount, writeCount - lastWriteCount,
readCount, readCount - lastReadCount,
gMaxReads, gMaxWriteWaits, gMaxReadWaits);
lastWriteCount = writeCount;
lastReadCount = readCount;
gMaxReads = gMaxWriteWaits = gMaxReadWaits = 0;
}
return 0;
}
static void padStack (int argc, char** argv)
{
char pad[512]; /* Work around bug in nspr on windoze */
pseudoMain (argc, argv, pad);
}
int main(int argc, char **argv)
{
PR_Init(PR_USER_THREAD, PR_PRIORITY_NORMAL, 0);
PR_STDIO_INIT();
padStack (argc, argv);
}
/* bug1test.c */
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