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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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