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From "Sorin Manolache" <>
Subject Re: null pollset
Date Thu, 08 Jan 2009 08:06:30 GMT
On Thu, Jan 8, 2009 at 03:13, Brian Adams <> wrote:
> Hi,
> I just created a new dev box on Fedora 10 and I'm seeing something strange with httpd
that I built from source.  It's segfaulting constantly (even though I can get pages and modules
to execute).  If I look at a coredump I see this:
> (gdb) where
> #0  apr_pollset_add (pollset=0x0, descriptor=0xbf8aadec) at poll/unix/epoll.c:150
> #1  0x080bd161 in child_main (child_num_arg=<value optimized out>) at prefork.c:532
> #2  0x080bd613 in make_child (s=0x8ee4830, slot=1) at prefork.c:746
> #3  0x080bdc9a in startup_children () at prefork.c:764
> #4  ap_mpm_run (_pconf=0x8edf550, plog=0x8f19638, s=0x8ee4830) at prefork.c:985
> #5  0x08069800 in main (argc=Cannot access memory at address 0x0
> ) at main.c:740
> Looks like apr_pollset_create is failing in prefork.c.  Any ideas on why this would happen?

Here you have a part of the code of apr_pollset_create.

child_main calls this function with flags = 0 and size =
num_listeners. I don't know how num_listeners is initialised. Anyway,
"man epoll_create" says that the size argument is ignored by

Anyway, I would recommend you to try a small program calling
epoll_create. It could be that you don't have a kernel compiled with
epoll (epoll_create returns -1).

APR_DECLARE(apr_status_t) apr_pollset_create(apr_pollset_t **pollset,
                                             apr_uint32_t size,
                                             apr_pool_t *p,
                                             apr_uint32_t flags)
    apr_status_t rv;
    int fd;

    fd = epoll_create(size);
    if (fd < 0) {
        *pollset = NULL;
        return errno;

    *pollset = apr_palloc(p, sizeof(**pollset));

// skipped the rest. If we reach here, pollset cannot be NULL anymore.
There's more code but "flags" being 0 makes sure that the code where
*pollset = NULL is not executed.

    return APR_SUCCESS;

> Thanks for the help.
> Brian

A: Because it reverses the logical flow of conversation.
Q: Why is top-posting frowned upon?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

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