coredump设置

coredump路径查看及设置

coredump路径查看

命令1： cat /proc/sys/kernel/core_pattern

命令2： /sbin/sysctl kernel.core_pattern

coredump路径修改

临时修改：echo ‘/var/log/%e.core.%p’ > /proc/sys/kernel/core_pattern

永久修改： /sbin/sysctl -w kernel.core_pattern=/var/log/%e.core.%p

如果是ubuntu系统，上述设置方法不生效，因为ubuntu中默认开启了系统错误诊断，这项配置会阻止"echo /home/core-%e-%p >/proc/sys/kernel/core_pattern "的操作。需要做如下设置：

- 关闭系统诊断

sudo vim /etc/default/apport
将文件中enabled设置为0
enabled=0

- 修改/etc/sysctl.conf文件

vim /etc/sysctl.conf
kernel.core_pattern = /corefile/core-%e-%p-%t

重启后查看coredump路径，设置成功。

coredump size设置

查看coredump size

ulimit -c 返回0则不会生成coredump

ulimit -c unlimited 设置coredump长度，不限长

强制生成coredump

kill -6 pid会强制生成coredump

如dead_lock_demo.cc

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>static int sequence1 = 0;
static int sequence2 = 0;pthread_mutex_t lock1;
pthread_mutex_t lock2;int func1(){pthread_mutex_lock(&lock1); ++sequence1; sleep(1); pthread_mutex_lock(&lock2); ++sequence2; pthread_mutex_unlock(&lock2); pthread_mutex_unlock(&lock1); return sequence1; 
}int func2(){pthread_mutex_lock(&lock2); ++sequence2; sleep(1); pthread_mutex_lock(&lock1); ++sequence2; pthread_mutex_unlock(&lock1); pthread_mutex_unlock(&lock2); return sequence1; 
}void* thread1(void *arg)
{int rev = 0;while(1){rev = func1();       if (rev == 100000){pthread_exit(NULL);}}
}void* thread2(void *arg)
{int rev = 0;while(1){rev = func2();       if (rev == 100000){pthread_exit(NULL);}}
}void* thread3(void *arg){int count = 0;while(1){sleep(1);if ( count++ > 10000){pthread_exit(NULL);}}
}void* thread4(void *arg){int count = 0;while(1){sleep(1);if ( count++ > 10000){pthread_exit(NULL);}}
}int main(){float a = 0.0334;float b = -0.0321;printf("abs(a)=%.4f,abs(b)=%.4f\n",fabs(a),fabs(b));pthread_t tid[4];    pthread_mutex_init(&lock1, NULL);pthread_mutex_init(&lock2, NULL);if(pthread_create(&tid[0], NULL, &thread1, NULL) != 0){_exit(1);}if(pthread_create(&tid[1], NULL, &thread2, NULL) != 0){_exit(1);}if(pthread_create(&tid[2], NULL, &thread3, NULL) != 0){_exit(1);}if(pthread_create(&tid[3], NULL, &thread4, NULL) != 0){_exit(1);}sleep(5);pthread_join(tid[0], NULL);pthread_join(tid[1], NULL);pthread_join(tid[2], NULL);pthread_join(tid[3], NULL);pthread_mutex_destroy( &lock1 );pthread_mutex_destroy( &lock2 );return 0;
}

执行g++ -Wall -std=c++11 dead_lock_demo.cc -o dead_lock_demo -g -pthread

运行

./dead_lock_demo

找到pid,kill -6 pid会生成coredump

调试coredump gdb dead_lock_demo core-dead_lock_demo

Thread 5 (Thread 0x7f883fb92700 (LWP 6840)):
#0  0x00007f884147a7a0 in __GI___nanosleep (requested_time=requested_time@entry=0x7f883fb91e90, remaining=remaining@entry=0x7f883fb91e90)at ../sysdeps/unix/sysv/linux/nanosleep.c:28
#1  0x00007f884147a67a in __sleep (seconds=0) at ../sysdeps/posix/sleep.c:55
#2  0x0000562321db4b37 in thread4 (arg=0x0) at dead_lock_demo.cc:73
#3  0x00007f884178e6db in start_thread (arg=0x7f883fb92700) at pthread_create.c:463
#4  0x00007f88414b771f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 4 (Thread 0x7f8840393700 (LWP 6839)):
#0  0x00007f884147a7a0 in __GI___nanosleep (requested_time=requested_time@entry=0x7f8840392e90, remaining=remaining@entry=0x7f8840392e90)at ../sysdeps/unix/sysv/linux/nanosleep.c:28
#1  0x00007f884147a67a in __sleep (seconds=0) at ../sysdeps/posix/sleep.c:55
#2  0x0000562321db4afb in thread3 (arg=0x0) at dead_lock_demo.cc:63
#3  0x00007f884178e6db in start_thread (arg=0x7f8840393700) at pthread_create.c:463
#4  0x00007f88414b771f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 3 (Thread 0x7f8840b94700 (LWP 6838)):
#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007f8841791025 in __GI___pthread_mutex_lock (mutex=0x562321fb6040 <lock1>) at ../nptl/pthread_mutex_lock.c:80
#2  0x0000562321db4a53 in func2 () at dead_lock_demo.cc:29
#3  0x0000562321db4ac8 in thread2 (arg=0x0) at dead_lock_demo.cc:53
#4  0x00007f884178e6db in start_thread (arg=0x7f8840b94700) at pthread_create.c:463
#5  0x00007f88414b771f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 2 (Thread 0x7f8841395700 (LWP 6837)):
#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007f8841791025 in __GI___pthread_mutex_lock (mutex=0x562321fb6080 <lock2>) at ../nptl/pthread_mutex_lock.c:80
#2  0x0000562321db49ef in func1 () at dead_lock_demo.cc:17
#3  0x0000562321db4a9a in thread1 (arg=0x0) at dead_lock_demo.cc:42
#4  0x00007f884178e6db in start_thread (arg=0x7f8841395700) at pthread_create.c:463
#5  0x00007f88414b771f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 1 (Thread 0x7f8841bb6740 (LWP 6836)):
#0  0x00007f884178fd2d in __GI___pthread_timedjoin_ex (threadid=140223186556672, thread_return=0x0, abstime=0x0, block=<optimized out>) at pthread_join_common.c:89
#1  0x0000562321db4cd3 in main () at dead_lock_demo.cc:106

从thread 堆栈信息看出，line17 ，line29发生死锁。

也可以不生成coredump调试，gdb attach pid （or sudo gdb attach pid）

thread apply all bt

和coredump一样的堆栈信息

(gdb) thread apply all btThread 5 (Thread 0x7f648932e700 (LWP 6949)):
#0  0x00007f648ac167a0 in __GI___nanosleep (requested_time=requested_time@entry=0x7f648932de90, remaining=remaining@entry=0x7f648932de90)at ../sysdeps/unix/sysv/linux/nanosleep.c:28
#1  0x00007f648ac1667a in __sleep (seconds=0) at ../sysdeps/posix/sleep.c:55
#2  0x000056036b638b37 in thread4 (arg=0x0) at dead_lock_demo.cc:73
#3  0x00007f648af2a6db in start_thread (arg=0x7f648932e700) at pthread_create.c:463
#4  0x00007f648ac5371f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 4 (Thread 0x7f6489b2f700 (LWP 6948)):
#0  0x00007f648ac167a0 in __GI___nanosleep (requested_time=requested_time@entry=0x7f6489b2ee90, remaining=remaining@entry=0x7f6489b2ee90)at ../sysdeps/unix/sysv/linux/nanosleep.c:28
#1  0x00007f648ac1667a in __sleep (seconds=0) at ../sysdeps/posix/sleep.c:55
#2  0x000056036b638afb in thread3 (arg=0x0) at dead_lock_demo.cc:63
#3  0x00007f648af2a6db in start_thread (arg=0x7f6489b2f700) at pthread_create.c:463
#4  0x00007f648ac5371f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 3 (Thread 0x7f648a330700 (LWP 6947)):
#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007f648af2d025 in __GI___pthread_mutex_lock (mutex=0x56036b83a040 <lock1>) at ../nptl/pthread_mutex_lock.c:80
#2  0x000056036b638a53 in func2 () at dead_lock_demo.cc:29
#3  0x000056036b638ac8 in thread2 (arg=0x0) at dead_lock_demo.cc:53
#4  0x00007f648af2a6db in start_thread (arg=0x7f648a330700) at pthread_create.c:463
#5  0x00007f648ac5371f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 2 (Thread 0x7f648ab31700 (LWP 6946)):
#0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135
#1  0x00007f648af2d025 in __GI___pthread_mutex_lock (mutex=0x56036b83a080 <lock2>) at ../nptl/pthread_mutex_lock.c:80
#2  0x000056036b6389ef in func1 () at dead_lock_demo.cc:17
#3  0x000056036b638a9a in thread1 (arg=0x0) at dead_lock_demo.cc:42
#4  0x00007f648af2a6db in start_thread (arg=0x7f648ab31700) at pthread_create.c:463
#5  0x00007f648ac5371f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95Thread 1 (Thread 0x7f648b352740 (LWP 6945)):
#0  0x00007f648af2bd2d in __GI___pthread_timedjoin_ex (threadid=140069800449792, thread_return=0x0, abstime=0x0, block=<optimized out>) at pthread_join_common.c:89
#1  0x000056036b638cd3 in main () at dead_lock_demo.cc:106