Re: [Lynx-dev] Re: lynx randomly hanging at "HTTP/1.1 200 OK"

[Thomas Dickey]

On Sat, 7 Jan 2006, Fr?d?ric L. W. Meunier wrote:

> BTW, something I forgot and could be relevant. I set LYNX_TEMP_SPACE=~/tmp 
> and ~/tmp is using tmpfs (half my RAM = 256Mb):
>
> tmpfs /home/fredlwm/tmp tmpfs defaults,gid=102,mode=0700,uid=1000 0 0
>
> The only thing I'm sure is that it never runs out of space when this happens 
> (and there are always less than 60 lynx files). And also that I've been using 
> it for years.

Perhaps some odd problem with the configure script is making the 
used_tempname[] array very small.  You can verify that by adding
a
        CTRACE((tfp, "SIZEOF_used_tempname=%d\n", sizeof(used_tempname)));

to the beginning of the function and looking for that in the trace.

If it were looping in the caller of fmt_tempname(), I'd suspect that the
directory permissions are making lynx decide that it's insecure.  But it
seems to be stuck in this loop:

    counter = MAX_TEMPNAME;
    while (names_used < MAX_TEMPNAME) {
        counter = (unsigned) (((float) MAX_TEMPNAME * lynx_rand()) /
                              LYNX_RAND_MAX + 1);
        counter %= SIZE_TEMPNAME;       /* just in case... */
        /*
         * Avoid reusing a temporary name, since there are places in the code
         * which can refer to a temporary filename even after it has been
         * closed and removed from the filesystem.
         */
        offset = counter / BITS_PER_CHAR;
        mask = 1 << (counter % BITS_PER_CHAR);
        if ((used_tempname[offset] & mask) == 0) {
            names_used++;
            used_tempname[offset] |= mask;
            break;
        }
    }
    if (names_used >= MAX_TEMPNAME)
        HTAlert(gettext("Too many tempfiles"));

which sounds as if either the array is small, or there's something wrong
with the random number generated (whatever lynx_rand() happens to be 
defined to).  Or else there's something wrong with my assumptions for
the computation - thinking about it, since it is scaled (dividing by 
LYNX_RAND_MAX), it may keep trying to use the same filenames repeatedly.

We can improve on this by changing the loop to simply look for an unused 
entry in the table:

    counter = MAX_TEMPNAME;
    if (names_used < MAX_TEMPNAME) {
        counter = (unsigned) (((float) MAX_TEMPNAME * lynx_rand()) /
                              LYNX_RAND_MAX + 1);
        /*
         * Avoid reusing a temporary name, since there are places in the code
         * which can refer to a temporary filename even after it has been
         * closed and removed from the filesystem.
         */
        do {
            counter %= SIZE_TEMPNAME;
            offset = counter / BITS_PER_CHAR;
            mask = 1 << (counter % BITS_PER_CHAR);
            if ((used_tempname[offset] & mask) == 0) {
                names_used++;
                used_tempname[offset] |= mask;
                break;
            }
        } while ((used_tempname[offset] & mask) == 0);
    }
    if (names_used >= MAX_TEMPNAME)


--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net