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    SubjectRe: Leap second insertion causes futex to repeatedly timeout
    On 2012.07.01 at 02:57 +0200, Jan Engelhardt wrote:
    >
    > This year's leap second insertion has had the strange effect on at least
    > Linux versions 3.4.4 (my end) and 3.5-rc4 (Simon's box, Cc) that certain
    > processes use up all CPU power, because of futexes repeatedly timing
    > out. This seems to only affect certain processes.
    >
    > Simon observes - http://s85.org/owXfmLvt - that
    > Firefox/Thunderbird/Chrome/Java are affected.

    On my ntp synchronized Linux 3.5 testbox I saw a similar issue.

    The leap second was successfully inserted last night:
    Jul 1 01:59:59 x4 kernel: Clock: inserting leap second 23:59:60 UTC

    Because glibc-2.16 was released yesterday I've build it this morning.
    During "make check" I saw several mutex related tests failures. For
    example /nptl/tst-mutex5a.c failed with a "premature timeout difference"
    of one second.

    tst-mutex5a.c:
    #define TYPE PTHREAD_MUTEX_ADAPTIVE_NP
    #include "tst-mutex5.c"

    from tst-mutex5.c:
    // ...
    gettimeofday (&tv, NULL);
    TIMEVAL_TO_TIMESPEC (&tv, &ts);

    ts.tv_sec += 2; /* Wait 2 seconds. */

    err = pthread_mutex_timedlock (&m, &ts);
    // ...
    {
    int clk_tck = sysconf (_SC_CLK_TCK);

    gettimeofday (&tv2, NULL);

    tv2.tv_sec -= tv.tv_sec;
    tv2.tv_usec -= tv.tv_usec;
    if (tv2.tv_usec < 0)
    {
    tv2.tv_usec += 1000000;
    tv2.tv_sec -= 1;
    }

    /* Be a bit tolerant, add one CLK_TCK. */
    tv2.tv_usec += 1000000 / clk_tck;
    if (tv2.tv_usec >= 1000000)
    {
    tv2.tv_usec -= 1000000;
    ++tv2.tv_sec;
    }

    if (tv2.tv_sec < 2)
    {
    printf ("premature timeout: %ld.%06ld difference\n",
    tv2.tv_sec, tv2.tv_usec);
    return 1;
    }
    }
    // ...

    --
    Markus


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