shared memory problem


 
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Operating Systems HP-UX shared memory problem
# 1  
Old 09-02-2006
shared memory problem

Hi, there
On HP-UX, there is a problem about shared memory. The code open the data file and use the "mmap" system call to map into the shared memory, when the contents are make changes, there is no effective on shared memory. The codes look like the following:
Code:
 ...
sysdb=shm_open(path,O_CREAT|O_RDWR,S_IRWXO|S_IRWXG|S_IRWXU);
if (sysdb==-1)
 {
   perror("main:shm_open system database error");
   exit(1);
 }
 if(ftruncate(sysdb,SYSDB_SIZE)==-1)
   {
      perror("main:ftruncate sysdb failure");
      exit(1);
   }
   sysdb_addr=(caddr_t)mmap(0,SYSDB_SIZE,PROT_READ|PROT_WRITE,MAP_SHARED,\
              sysdb,0);
   if(sysdb_addr==(caddr_t)-1)
   {
      perror("main:system database mmap error");
      exit(1);
   }
   sysdb_header=(DB_HEADER *)sysdb_addr;
  
  ...

on the above codes, when the data changes in the file specified by 'path',
the value pointed by 'sysdb_addr' is still original.
Anyone can give some suggestion? thanks.

Last edited by blowtorch; 09-05-2006 at 03:31 AM.. Reason: put in code tags
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