lkml.org 
[lkml]   [2012]   [Nov]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH RESEND 1/3] printk: convert byte-buffer to variable-length record buffer
    On Thu, Nov 29, 2012 at 2:28 PM, Kay Sievers <kay@vrfy.org> wrote:
    > On Thu, Nov 29, 2012 at 2:18 PM, Michael Kerrisk (man-pages)
    > <mtk.manpages@gmail.com> wrote:
    >> On Wed, Nov 28, 2012 at 6:51 PM, Kay Sievers <kay@vrfy.org> wrote:
    >
    >>> Before:
    >>> syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 286965
    >>> syslog(SYSLOG_ACTION_READ_CLEAR, "<12>"..., 1000000) = 24000
    >>> syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 286965
    >>>
    >>> After:
    >>> syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 90402
    >>> syslog(SYSLOG_ACTION_READ_CLEAR, "<5>"..., 1000000) = 90402
    >>> syslog(SYSLOG_ACTION_SIZE_UNREAD, 0, 0) = 0
    >
    >> I'm going to call my report yesterday bogus. Somewhere along the way,
    >> I got confused while testing something, and my statement about 2.6.31
    >> behavior is wrong: the 2.6.31 and 3.5 behaviors are the same. As such,
    >> your patch is unneeded. Sorry for wasting your time.
    >
    > I think you have been right with your report. The above pasted
    > before/after from the patch commit text is actually a result of real
    > testing with current git. And your initial description sounds right,
    > and the patch seems to produce the expected results here. I just
    > confused the numbers in your report and wrongly parsed 2.6 > 3.6.
    >
    > Hmm, at least do far we did not blame anybody else than ourselves as
    > confused. One of us at least is right, and it looks you have been, and
    > I also think the patch is at least intended to be right. :)

    Okay -- I'm pretty sure I am right about being wrong ;-).

    Could you do some comparative testing please between 3.5 and pre-3.5.
    I have a little test program below. When I rechecked 2.6.31 and 3.5
    using this program I found the behavior was the same, which is why I
    conclude my report is wrong. (And also, your proposed patch in
    response to my bogus report produces different behavior from 2.6.31).

    Thanks,

    Michael

    /*#* t_klogctl.c

    klogctl(3) is the glibc interface for syslog(2)

    */

    #include <sys/klog.h>
    #include <sys/types.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <string.h>
    #include <errno.h>

    #define errMsg(msg) do { perror(msg); } while (0)

    #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \
    } while (0)

    #define fatal(msg) do { fprintf(stderr, "%s\n", msg); \
    exit(EXIT_FAILURE); } while (0)


    /* Close the log. Currently a NOP. */
    #define SYSLOG_ACTION_CLOSE 0
    /* Open the log. Currently a NOP. */
    #define SYSLOG_ACTION_OPEN 1
    /* Read from the log. */
    #define SYSLOG_ACTION_READ 2
    /* Read all messages remaining in the ring buffer. */
    #define SYSLOG_ACTION_READ_ALL 3
    /* Read and clear all messages remaining in the ring buffer */
    #define SYSLOG_ACTION_READ_CLEAR 4
    /* Clear ring buffer. */
    #define SYSLOG_ACTION_CLEAR 5
    /* Disable printk's to console */
    #define SYSLOG_ACTION_CONSOLE_OFF 6
    /* Enable printk's to console */
    #define SYSLOG_ACTION_CONSOLE_ON 7
    /* Set level of messages printed to console */
    #define SYSLOG_ACTION_CONSOLE_LEVEL 8
    /* Return number of unread characters in the log buffer */
    #define SYSLOG_ACTION_SIZE_UNREAD 9
    /* Return size of the log buffer */
    #define SYSLOG_ACTION_SIZE_BUFFER 10


    int
    main(int argc, char *argv[])
    {
    int s;
    #define BSIZE 500000
    char buf[BSIZE];

    if (argc < 2) {
    fprintf(stderr, "Usage: %s command-num [arg]\n", argv[0]);
    exit(EXIT_FAILURE);
    }

    int cmd;

    cmd = atoi(argv[1]);

    switch (cmd) {

    case SYSLOG_ACTION_READ: /* 2 */
    printf("SYSLOG_ACTION_READ\n");
    s = klogctl(SYSLOG_ACTION_READ, buf,
    (argc > 2) ? atoi(argv[2]) : BSIZE);
    if (s == -1)
    errExit("klogctl-READ");
    printf("Return value: %d\n", s);

    if (write(2, buf, s) != s)
    errMsg("write");
    break;

    case SYSLOG_ACTION_READ_ALL: /* 3 */
    case SYSLOG_ACTION_READ_CLEAR: /* 4 */
    if (cmd == SYSLOG_ACTION_READ_CLEAR)
    printf("SYSLOG_ACTION_READ_CLEAR\n");
    else
    printf("SYSLOG_ACTION_READ_ALL\n");


    s = klogctl(cmd, buf,
    (argc > 2) ? atoi(argv[2]) : BSIZE);
    if (s == -1)
    errExit("klogctl-READ_ALL/READ_CLEAR");
    printf("Return value: %d\n", s);

    if (write(2, buf, s) != s)
    errMsg("write");

    if (cmd == SYSLOG_ACTION_READ_CLEAR)
    printf("Ring buffer cleared\n");
    break;

    case SYSLOG_ACTION_CLEAR: /* 5 */
    printf("SYSLOG_ACTION_CLEAR\n");
    s = klogctl(SYSLOG_ACTION_CLEAR, NULL, 0);
    if (s == -1)
    errExit("klogctl-CLEAR");
    printf("Return value: %d\n", s);
    printf("Ring buffer cleared\n");
    break;

    case SYSLOG_ACTION_SIZE_UNREAD: /* 9 */
    printf("SYSLOG_ACTION_SIZE_UNREAD\n");
    s = klogctl(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0);
    if (s == -1)
    errExit("klogctl-SIZE_UNREAD");
    printf("Number of unread bytes: %d\n", s);
    break;

    case SYSLOG_ACTION_SIZE_BUFFER: /* 10 */
    printf("SYSLOG_ACTION_SIZE_BUFFER\n");
    s = klogctl(SYSLOG_ACTION_SIZE_BUFFER, NULL, 0);
    if (s == -1)
    errExit("klogctl-SIZE_BUFFER");
    printf("Size of buffer: %d\n", s);
    break;

    default:
    fatal("Bad command");
    break;
    }

    exit(EXIT_SUCCESS);
    }


    \
     
     \ /
      Last update: 2012-11-29 15:21    [W:3.316 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site