Re: [PATCH] Fix POD reading...

[Justin Erenkrantz <je...@ebuilt.com>]

[ Moving to dev@apr since this is now an APR issue ]

On Fri, Jul 20, 2001 at 10:58:49AM -0400, Jeff Trawick wrote:
> I'd first look into what happens if we use O_NONBLOCK instead of
> O_NDELAY on Solaris.  That is the simplest fix, and it avoids the need
> to add extra pathlength to apr_read().

Well, first we should already be using O_NONBLOCK with pipes (I 
checked with gcc -E) - APR is using flag 0x80 which is Solaris's 
definiton for O_NONBLOCK.

According to the man page, we're seeing what would happen if O_NDELAY 
is set - not what would happen if we had O_NONBLOCK set.  Odd.

Something funny is going on here or I'm incredibly stupid.  I'll try 
and recreate this again.  -- justin

Re: [PATCH] Fix POD reading...

[Justin Erenkrantz <je...@ebuilt.com>]

Here is my testpipe.c which shows the problem on Solaris.

Whether PIPE_AS_SOCKET is defined doesn't seem to matter, but notice
that with the pipe it doesn't read 64000 times.  Odd.  To state the 
obvious, -nohack is when SOLARIS_HACK is undefined.  -hack is when 
SOLARIS_HACK is defined.

jerenkrantz@dogbert% wc -c file-nohack
   64000 file-nohack
jerenkrantz@dogbert% wc -c file-hack
    1000 file-hack
jerenkrantz@dogbert% wc -c pipe-nohack
   63936 pipe-nohack
jerenkrantz@dogbert% wc -c pipe-hack
    1000 pipe-hack

Anyone else is welcome to see if they can reproduce this (maybe you can
spot something bad in my code - but this is close to how the threaded
MPM does it).  I'm going to keep looking.  -- justin

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#include <stdio.h>
#include "apr_file_io.h"
#include "apr_errno.h"
#include "apr_general.h"
#include "apr_lib.h"
#include "apr_network_io.h"
#include <stdlib.h>
#include <unistd.h>

apr_file_t *readp = NULL;
apr_file_t *writep = NULL;

#define PIPE_AS_SOCKET
#define SOLARIS_HACK

void pipe_child()
{
    char b = ' ';
    int one = 1;
    int i = 0;
    apr_status_t ret;
#ifdef PIPE_AS_SOCKET
    apr_socket_t *s;
    apr_socket_from_file(&s, readp);
#endif
    while (i < 1000)
    {
#ifdef PIPE_AS_SOCKET
        ret = apr_recv(s, &b, &one);
#else
        ret = apr_file_read(readp, &b, &one)
#endif
        if (APR_STATUS_IS_EAGAIN(ret)) {
            /* It lost the lottery. It must continue to suffer
             * through a life of servitude. */
        }
        else {
#ifdef SOLARIS_HACK
            if (one == 1)
                printf("%c", b);
#else
            printf("%c", b);
#endif
        }
        i++;
    }
}

void pipe_parent()
{
    char c = '!';
    int one = 1;
    int i = 0;
    while (i < 1000)
    {
        apr_file_write(writep, &c, &one);
        i++;
    } 
}

void go()
{
    fflush(stdout);
    if (fork())
    {
        fork();
        fork();
        fork();
        fork();
        fork();
        fork();
        pipe_child();
    }
    else
    {
        pipe_parent();
    }
}

int main(void)
{
    apr_pool_t *context;
    apr_size_t nbytes;
    apr_status_t rv;
    char *buf;
    char msgbuf[120];

    if (apr_initialize() != APR_SUCCESS) {
        exit(-1);
    }
    atexit(apr_terminate);
    if (apr_pool_create(&context, NULL) != APR_SUCCESS) {
        exit(-1);
    }

    if ((rv = apr_file_pipe_create(&readp, &writep, context)) != APR_SUCCESS) {
        exit(-1);
    }
    
    if ((rv = apr_file_pipe_timeout_set(readp, 1 * APR_USEC_PER_SEC)) != 
        APR_SUCCESS) {
        exit(-1);
    }        

    go();
    return 1;
}