From mboxrd@z Thu Jan  1 00:00:00 1970
From: yannick.brosseau@gmail.com (Yannick Brosseau)
Date: Mon, 21 Feb 2011 14:50:59 -0500
Subject: [ltt-dev] [UST] open_buffers_list in tracectl.c
Message-ID: <4D62C223.3080504@gmail.com>

Question for UST experts (Nils?)

While trying to fix the fork case, I've found problems with the the
open_buffers_list. I've fixed the segfault by moving the
ltt_trace_destroy later in ust_fork, but now I get some warnings about
already closed file descriptor.
It seems that we try to close the fd twice.
Now I'm wondering if we really need to close the fd referenced by the
open buffers list in ust_fork()? All these FD are closed when we destroy
the channels in the call to ltt_trace_destroy, so it seems redundant to
me. 

Am I missing something?

For quick reference here's the code using open_buffer_list from
tracectl.c in ust_fork(void)

    /* Delete all blocked consumers */
    cds_list_for_each_entry_safe(buf, buf_tmp, &open_buffers_list,
                 open_buffers_list) {
        result = close(buf->data_ready_fd_read);
        if (result == -1) {
            PERROR("close");
        }
        result = close(buf->data_ready_fd_write);
        if (result == -1) {
            PERROR("close");
        }
        cds_list_del(&buf->open_buffers_list);
    }

It would  suggest to change it to simply

    /* Empty the list of open buffers */
    cds_list_for_each_entry_safe(buf, buf_tmp, &open_buffers_list,
                 open_buffers_list) {
        cds_list_del(&buf->open_buffers_list);
    }