The putback for 6565503 "callout processing is single threaded, throttling
applications that rely on scalable callouts" in build 103 apparently has
changed the kernel function cv_waituntil_sig() to create callouts with
a new flag CALLOUT_FLAG_HRESTIME. This flag is described in
uts/common/sys/callo.h as:
* CALLOUT_FLAG_HRESTIME
* Normally, callouts are not affected by changes to system time
* (hrestime). This flag is used to create a callout that is affected
* by system time. If system time changes, these timers must expire
* at once. These are used by condition variables and LWP timers that
* need this behavior.
cv_waituntil_sig() is used with several system calls (poll() / select() /
sigtimedwait(), semtimedop(), ...). What I'm observing is that with
build 103 or newer all of these system calls return prematurely -
before the timeout expires - when the system time is set (e.g. by
ntp / ntpdate or rdate).
Test cases are:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main(int argc, char **argv)
{
struct timeval tv;
int i;
tv.tv_sec = 250;
tv.tv_usec = 0;
i = select(0, NULL, NULL, NULL, &tv);
if (i < 0) {
perror("select");
exit(1);
}
printf("select returned %d\n", i);
exit(0);
}
-----------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
int
main(int argc, char **argv)
{
sigset_t set;
siginfo_t info;
struct timespec tmout;
sigemptyset(&set);
sigaddset(&set, SIGALRM);
tmout.tv_sec = 250;
tmout.tv_nsec = 0;
sigtimedwait(&set, &info, &tmout);
}
-----------------------------------------------
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
int
main(int argc, char **argv)
{
int sem;
struct sembuf ops[1];
struct timespec ts;
sem = semget(IPC_PRIVATE, 1, 0600);
if (sem < 0) {
perror("semget");
exit(1);
}
ops[0].sem_num = 0;
ops[0].sem_op = -1;
ops[0].sem_flg = 0;
ts.tv_sec = 250;
ts.tv_nsec = 0;
semtimedop(sem, ops, 1, &ts);
}
If you start any one of these on build 103 or newer
and run "rdate {time-server}" or set the date with
"date HHMM" in another window, the system call
gets a timeout and the program terminates.
Expected behavior would be that these programs
wait 250 seconds for some event, and changing
the system clock does not affect waiting.
Is this a bug or a feature of 6565503?
Btw. the changed timeout for poll() behavior did break hald:
Bug ID: 6792302
Synopsis: hald occasionally exits on startup with status 2
http://bugs.opensolaris.org/view_bug.do?bug_id=6792302
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