Date: Tue, 19 Dec 2006 12:29:35 -0800 From: Garrett Cooper <youshi10@u.washington.edu> To: freebsd-current@freebsd.org Subject: Re: settimeofday function taking 24 - 30 minutes to complete Message-ID: <6EBDAA3A-A78C-4AA2-B9B7-E94C5C7DB186@u.washington.edu> In-Reply-To: <9ab217670612191201y47b7bb3codf979f88f56e81cc@mail.gmail.com> References: <790a9fff0612190915va75678at895efa0bc93ac3a1@mail.gmail.com> <458843B8.1060704@u.washington.edu> <9ab217670612191201y47b7bb3codf979f88f56e81cc@mail.gmail.com>
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On Dec 19, 2006, at 12:01 PM, Devon H. O'Dell wrote:
> 2006/12/19, Garrett Cooper <youshi10@u.washington.edu>:
>> Scot Hetzel wrote:
>> > While working on implementing the settimeofday function in the
>> > linuxolator, I was using the LTP testcase settimeofday01 to test
>> it.
>> > Running this test caused the system to hang for 24-30 minutes.
>> >
>> > I then decided to rewrite the testcase so that it would run on
>> > FreeBSD, and it also hung the system for 24-30 minutes. What the
>> > settimeofday01 test was doing is to set the time to a known
>> value (100
>> > sec, 100 usec) and then use gettimeofday to retrieve the current
>> time.
>> > It then compared the returned value to check if it was within
>> +/- 500
>> > msec.
>> >
>> > I have since reduced the testcode down to the following testcase
>> that
>> > is causing the hang.
>> >
>> > Any ideals as to what could be causing this hang?
>> >
>> > Scot
>> >
>> > #include <sys/time.h>
>> > #include <errno.h>
>> > #include <unistd.h>
>> >
>> > #define VAL_SEC 100
>> > #define VAL_MSEC 100
>> >
>> > int main(int argc, char **argv)
>> > {
>> > struct timeval tp, tp1, save_tv;
>> > long return_test, errno_test;
>> > suseconds_t delta;
>> >
>> > #define TEST(SCALL) \
>> > do { \
>> > errno = 0; \
>> > return_test = SCALL; \
>> > errno_test = errno; \
>> > } while (0)
>> >
>> > /* Save the current time values */
>> > if ((gettimeofday(&save_tv, (struct timezone *)&tp1)) ==
>> -1) {
>> > printf("BROK: gettimeofday failed. errno=%d\n",
>> errno);
>> > exit(1);
>> > } else {
>> > printf("INFO: Saved current time\n");
>> > }
>> >
>> > tp.tv_sec = VAL_SEC;
>> > tp.tv_usec = VAL_MSEC;
>> >
>> > /* Hang occurs here */
>> > TEST(settimeofday(&tp, NULL));
>> > if (return_test == -1) {
>> > printf("FAIL: Error Setting Time, errno=%d\n",
>> > errno_test);
>> > } else {
>> > printf("INFO: settimeofday completed sucessfully
>> \n");
>> > }
>> >
>> > /* restore the original time values. */
>> > if ((settimeofday(&save_tv, NULL)) == -1) {
>> > printf("WARN: FATAL COULD NOT RESET THE CLOCK\n");
>> > printf("FAIL: Error Setting Time, errno=%d (%d, %
>> d)\n",
>> > errno, tp.tv_sec, tp.tv_usec);
>> > } else {
>> > printf("INFO: Reset time to original value\n");
>> > }
>> >
>> > return(0);
>> > }
>> >
>> Not sure about why it takes so long to complete, but it seems
>> as if
>> the system is 'hanging' because it probably is using up all of
>> your CPU
>> resources in the while loop under your TEST macro. Maybe the near
>> 100%
>> CPU usage is effecting kernel operations as well, i.e. slowing it
>> down
>> to stone age speeds? sleep(3)/nanosleep(2) to the rescue?
>
> The while loop in the TEST macro is a do { /* ... */ } while (0); so
> it should only execute once.
>
> --Devon
Comes back near instantly, unsuccessful as a regular user and
successful as superuser under OS X. Trying linux now..
-Garrett
PS You didn't include stdio.h or stdlib.h and the compiler (gcc)
complained quite a bit.
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