Process page file usage in C

[mistretzu]

Hi all,

I'm using this code to obtain the process page file usage:

long getProcessPageFileUsage()
{
    int pid;
    char name[1024];
    char state;
    int ppid, pgrp, session, tty, tpgid;
    unsigned flags, minflt, cminflt, majflt, cmajflt;
    int utime, stime, cutime, cstime, counter, priority, timeout;
    unsigned itrealvalue, starttime, vsize = 0, rss = 0;

    FILE *f = fopen("/proc/self/stat", "r");
    
    fscanf(f, "%d %s %c %d %d %d %d %d %u "
              "%u %u %u %u %d %d %d "
              "%d %d %d %u %u %d "
	      "%u %u",
        &pid, name, &state, &ppid, &pgrp, &session, &tty, &tpgid, &flags,
        &minflt, &cminflt, &majflt, &cmajflt, &utime, &stime, &cutime,
        &cstime, &counter, &priority, &timeout, &itrealvalue, &starttime,
        &vsize, &rss);

    fclose(f);

    return rss * sysconf(_SC_PAGESIZE);
}

The problem is that it randomly crashes in fscanf().
That code is taken from http://www.cgal.org/Manual/3.2/inclu...Memory_sizer.h

I'm calling it from Java, so I have the hot spot crash log:

Stack: [0x746f1000,0x74742000],  sp=0x747406b8,  free space=317k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C  [libc.so.6+0x472a3]  _IO_vfscanf+0xa3
C  [libc.so.6+0x4c6a1]  vfscanf+0x31
C  [libc.so.6+0x50c2f]  fscanf+0x1f
C  [libnatutil.so+0x19e48]  _Z23getProcessPageFileUsagev+0xfe
C  [libnatutil.so+0x19e87]  Java_com_sync_util_NatUtil_getProcessPageFileUsage+0x17

Any ideas why it is failing? Besides checking the file pointer not to be NULL. Performing a read lock on that file, I don't think it will help. Since the kernel is changing the file.

[wje_lf]

That's puzzling, for sure. As a matter of superstition, I never use fscanf(). Try declaring a local

char fred[1024];

and doing an fgets() followed by an sscanf(), just to see what happens.