Very Computer

> Hi, All

>     I use clone() to create thread in LINUX. the call of clone is as
> follows:
>         for(i = 0; i < n; i++) {
>             if((stack[i] = (char*)malloc(CHILD_STACK * sizeof(char)))
> == NULL) {
>                        fprintf(stderr, "<main>malloc stack error.");
>                        exit(-1);
>             }
>             parm[i] = i;
>             if((pid[i] = clone(child_send_process, stack[i] +
> CHILD_STACK, CLONE_VM|CLONE_FILES, &parm[i])) < 0) {
>                        fprintf(stderr, "<main>clone send_child_process
> error.");
>                        exit(-1);
>             }
>         }
>     so n threads are created. But some of the thread will encounter
> segmentation fault after runing some time. I am sure the pointer
> allocated by my code is released correctly and the stack size here is
> 3M bytes.
>     Can anybody tell me some possibilities which will case segfault in
> thread made by clone()??

> Thanks.

> ----Kent

>> Hi, All

>>     I use clone() to create thread in LINUX. the call of clone is as
>> follows:
>>         for(i = 0; i < n; i++) {
>>             if((stack[i] = (char*)malloc(CHILD_STACK * sizeof(char)))
>> == NULL) {
>>                        fprintf(stderr, "<main>malloc stack error.");
>>                        exit(-1);
>>             }
>>             parm[i] = i;
>>             if((pid[i] = clone(child_send_process, stack[i] +
>> CHILD_STACK, CLONE_VM|CLONE_FILES, &parm[i])) < 0) {
>>                        fprintf(stderr, "<main>clone send_child_process
>> error.");
>>                        exit(-1);
>>             }
>>         }
>>     so n threads are created. But some of the thread will encounter
>> segmentation fault after runing some time. I am sure the pointer
>> allocated by my code is released correctly and the stack size here is
>> 3M bytes.
>>     Can anybody tell me some possibilities which will case segfault in
>> thread made by clone()??

>> Thanks.

>> ----Kent

> Same reasons as any other code + race conditions. How does your code
> work - do you create a thread pool or do you create a new thread to
> handle each new request? Is all access to shared variables protected by
> mutexes or semaphores?

> Have you considered using fork instead of clone? Using fork can solve a
> lot of problems, it is usually worth the extra effort of communicating
> shared information via anonymous pipes rather than via direct access to
> shared memory.

> You could also try installing Electric Fence or a similar memory
> debugging tool, this will help you isolate faulty memory management
> code.

> >> Hi, All

> >>     I use clone() to create thread in LINUX. the call of clone is as
> >> follows:
> >>         for(i = 0; i < n; i++) {
> >>             if((stack[i] = (char*)malloc(CHILD_STACK * sizeof(char)))
> >> == NULL) {
> >>                        fprintf(stderr, "<main>malloc stack error.");
> >>                        exit(-1);
> >>             }
> >>             parm[i] = i;
> >>             if((pid[i] = clone(child_send_process, stack[i] +
> >> CHILD_STACK, CLONE_VM|CLONE_FILES, &parm[i])) < 0) {
> >>                        fprintf(stderr, "<main>clone send_child_process
> >> error.");
> >>                        exit(-1);
> >>             }
> >>         }
> >>     so n threads are created. But some of the thread will encounter
> >> segmentation fault after runing some time. I am sure the pointer
> >> allocated by my code is released correctly and the stack size here is
> >> 3M bytes.
> >>     Can anybody tell me some possibilities which will case segfault in
> >> thread made by clone()??

> >> Thanks.

> >> ----Kent

> > Same reasons as any other code + race conditions. How does your code
> > work - do you create a thread pool or do you create a new thread to
> > handle each new request? Is all access to shared variables protected by
> > mutexes or semaphores?

> > Have you considered using fork instead of clone? Using fork can solve a
> > lot of problems, it is usually worth the extra effort of communicating
> > shared information via anonymous pipes rather than via direct access to
> > shared memory.

> > You could also try installing Electric Fence or a similar memory
> > debugging tool, this will help you isolate faulty memory management
> > code.
> And last, is there any reason to use clone directly and not pthreads
> (if threads are what one want ?)

> I have a share memory and fd between these two processes. so thread is
> suitable for me instead of using fork().

> How to use eletric fence? If segfault appeared, How can i trace back
> to find where the error is?

> thanks

>> >> Hi, All

>> >>     I use clone() to create thread in LINUX. the call of clone is as
>> >> follows:
>> >>         for(i = 0; i < n; i++) {
>> >>             if((stack[i] = (char*)malloc(CHILD_STACK * sizeof(char)))
>> >> == NULL) {
>> >>                        fprintf(stderr, "<main>malloc stack error.");
>> >>                        exit(-1);
>> >>             }
>> >>             parm[i] = i;
>> >>             if((pid[i] = clone(child_send_process, stack[i] +
>> >> CHILD_STACK, CLONE_VM|CLONE_FILES, &parm[i])) < 0) {
>> >>                        fprintf(stderr, "<main>clone send_child_process
>> >> error.");
>> >>                        exit(-1);
>> >>             }
>> >>         }
>> >>     so n threads are created. But some of the thread will encounter
>> >> segmentation fault after runing some time. I am sure the pointer
>> >> allocated by my code is released correctly and the stack size here is
>> >> 3M bytes.
>> >>     Can anybody tell me some possibilities which will case segfault in
>> >> thread made by clone()??

>> >> Thanks.

>> >> ----Kent

>> > Same reasons as any other code + race conditions. How does your code
>> > work - do you create a thread pool or do you create a new thread to
>> > handle each new request? Is all access to shared variables protected by
>> > mutexes or semaphores?

>> > Have you considered using fork instead of clone? Using fork can solve a
>> > lot of problems, it is usually worth the extra effort of communicating
>> > shared information via anonymous pipes rather than via direct access to
>> > shared memory.

>> > You could also try installing Electric Fence or a similar memory
>> > debugging tool, this will help you isolate faulty memory management
>> > code.
>> And last, is there any reason to use clone directly and not pthreads
>> (if threads are what one want ?)

> I have heard that pthread in linux is not so stable for High
> Availability Program which needs 7x24 peformance. So I use clone()
> instead of pthread.

>>I have heard that pthread in linux is not so stable for High
>>Availability Program which needs 7x24 peformance. So I use clone()
>>instead of pthread.

> AFAIK pthread and clone are both stable.