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List:       uclibc-cvs
Subject:    [Bug 7220] New: thread can'=?UTF-8?Q?t=20be=20scheduled=EF=BC=88pthread=5Fmutex=5Flock=EF=BC=89?=
From:       bugzilla () busybox ! net
Date:       2014-06-21 3:40:44
Message-ID: bug-7220-159 () https ! bugs ! busybox ! net/
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https://bugs.busybox.net/show_bug.cgi?id=7220

           Summary: thread can't be scheduled（pthread_mutex_lock）
           Product: uClibc
           Version: 0.9.33.3
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P5
         Component: Threads
        AssignedTo: unassigned@uclibc.org
        ReportedBy: jh@yealink.com
                CC: uclibc-cvs@uclibc.org
   Estimated Hours: 0.0


Linux version:
Linux version 3.4.20-rt31+

gcc version:
gcc version 4.6.4 20120303 (prerelease) (GCC)

processor infomation:
Processor       : ARM926EJ-S rev 5 (v5l)
BogoMIPS        : 199.06
Features        : swp half thumb fastmult edsp java 

testing procedure:
1.build test code
# arm-dspg-linux-uclibceabi-gcc -o lock_test pthread_lock_test.c -lpthread
-Wall
2.run at linux shell
# ./lock_test 
212121212121211111111111111111111111111111111111111111^C
# 
# ./lock_test 
12211221211221122121212112212121212121^C
# 
# ./lock_test 
12211212121221111111111111111111111111111111111111111111111111^C
# ./lock_test 
122112211212211221121221122112212112211221212121122121212121212121212121212121212121212222222222222222222222222222222222222222222222222222222222222222222^C
 # 

The results of the analysis：
1.When problems arise PC at pthread_mutex_lock function call can not quit,this
thread can't be scheduled(stopped).
2.Two threads(thread1,thread2) are likely happen.

test code：pthread_lock_test.c
/*************************************************/
#include <unistd.h> 
#include <pthread.h> 
#include <string.h> 
#include <stdio.h>
#include <linux/futex.h>
#include <sys/time.h>
#include <errno.h>

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

static int sequence1 = 0; 
static int sequence2 = 0; 

int func1() 
{
    pthread_mutex_lock(&mutex);
    ++sequence1;
    pthread_mutex_unlock(&mutex); 

    if(sequence1 % 60000 == 0)
        write(2, "1", 1);

    return 0;
} 

int func2() 
{
    pthread_mutex_lock(&mutex); 
    ++sequence2;
    pthread_mutex_unlock(&mutex);

    if(sequence2 % 60000 == 0)
        write(2, "2", 1);

    return 0;
} 

void* thread1(void* arg) 
{ 
    while (1)
        func1();
} 

void* thread2(void* arg) 
{ 
    while (1)
        func2();
} 

int main() 
{ 
    pthread_t tid[2];

    if (pthread_create(&tid[0], NULL, &thread1, NULL) != 0) 
    { 
        _exit(1); 
    } 
    if (pthread_create(&tid[1], NULL, &thread2, NULL) != 0) 
    { 
        _exit(1); 
    }

    while(1)
        sleep(50000000); 

    return 0; 
}

/*************************************************/

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