Re: problem with MAP_SHARED|MAP_ANONYMOUS mapping in openMosix-2.4.26-1

Sir,

May be you are modifying /proc/pid/migrate manually, in this case -1 will 
be returned by the write system call because of the condition check in 
proc_mosix_pid_set_migrate() in hpc/hpcproc.c .

1673	if (task != current)
1674               return (-EPERM);


if the process_to_be_migrated, itself (sharing MAP_SHARED|MAP_ANONYMOUS 
page with some other process) writesB some node no in /proc/pid/migrate 
then it is migrating(it should not migrate) and giving wrong result.

OR if you manually modify /proc/pid/goto, it is migrating.

I am attaching the om_test.c which is forking a child and writing a node 
no in /proc/pid/migrate.

Ratna

On Sun, 25 Sep 2005, Moshe Bar wrote:

> Ratna
>
> Just tried to recreate the problem and I can't. It's not migrating the
> process when I use mmap shared.
>
> Moshe
>
> On 9/25/05, Ratna Manoj Bolla <[email protected]> wrote:
>>
>>
>>
>> //-----------------------------------------------------------------------------
>> #include<stdio.h>
>> #include<sys/mman.h>
>> #include <sys/types.h>
>> #include <sys/stat.h>
>> #include <fcntl.h>
>> main() {
>> int *a =
>> mmap(0,4096,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,0,0);
>> *a = 0;
>> if(fork())
>> while(1) { sleep(2); ++(*a); }
>> else
>> while(1) { printf("%d\n",*a); sleep(2); }
>> }
>>
>>
>> //------------------------------------------------------------------------------
>>
>> The output of this program should be
>> 0
>> 1
>> 2
>> 3
>> .
>> .
>>
>> but output would remain constant after migrating one of the processes.
>>
>> openMosix shold not allow migrating processes sharing
>> MAP_SHARED|MAP_ANONYMOUS pages.
>>
>> from,
>> Ratna Manoj Bolla,
>> M.Tech IInd year,
>> dept. of CSE,
>> Indian Institute of Technology,
>> Guwahati,
>> India.
>>
>>
>>
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>

/* output should be:
child:0
parent:1
child:1
parent:2
child:2
parent:3
child:3
parent:4
child:4
parent:5
CHild MIGRATED TO NODE 1
child:6
parent:6
child:7
parent:7
child:8
parent:8
child:9
parent:9
but it is giving:
child:0
parent:1
child:1
parent:2
child:2
parent:3
child:3
parent:4
child:4
parent:5
CHild MIGRATED TO NODE 1
child:6
parent:6
child:6
parent:7
child:6
parent:8
child:6
parent:9

*/
#include<stdio.h>
#include<sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
char *pid2proc_path(int);
char path[50];
main() {
	int *a = mmap(0,4096,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,0,0);
	*a = 0;
	if(fork()) {
		while(1) {	
			sleep(1); 
			++(*a); 
			printf("parent:%d\n",*a);	
		}
	}
	else {
		while(1) {
	 		printf("child:%d\n",*a);  
			sleep(1); 
			if((*a) == 5) {
                                int fd = open(pid2proc_path(getpid()),O_RDWR);
                                char ch = '1'; // Migrating child to node no 1 in my cluster
                                if(write(fd,&ch,1) == 1)  printf("CHild MIGRATED TO NODE 1\n");
				*a = 6;
                        }
		}
	}
}
char *pid2proc_path(int pid) {      // Ex: from process-id:7014 to '/proc/7014/migrate'
	char a[10];
	int i;
	a[i=9] = 0;
	do {
		a[--i] = pid%10 + '0';
		pid /= 10;
	}while(pid!=0);
	strcpy(path,"/proc/");
 	strcat(path,a+i);
	strcat(path,"/migrate");	
	return path;
}