Date: Wed, 6 Mar 2013 22:40:47 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r247903 - head/sys/kern Message-ID: <201303062240.r26MelaH095463@svn.freebsd.org>
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Author: mav Date: Wed Mar 6 22:40:47 2013 New Revision: 247903 URL: http://svnweb.freebsd.org/changeset/base/247903 Log: Reduce minimal time intervals of setitimer(2) from 1/HZ to 1/(16*HZ) by using callout_reset_sbt() instead of callout_reset(). We can't remove lower limit completely in this case because of significant processing overhead, caused by unability to use direct callout execution due to using process mutex in callout handler for sending SEGALRM signal. With support of periodic events that would allow unprivileged user to abuse the system. Reviewed by: davide Modified: head/sys/kern/kern_time.c Modified: head/sys/kern/kern_time.c ============================================================================== --- head/sys/kern/kern_time.c Wed Mar 6 22:12:45 2013 (r247902) +++ head/sys/kern/kern_time.c Wed Mar 6 22:40:47 2013 (r247903) @@ -691,7 +691,7 @@ kern_getitimer(struct thread *td, u_int *aitv = p->p_realtimer; PROC_UNLOCK(p); if (timevalisset(&aitv->it_value)) { - getmicrouptime(&ctv); + microuptime(&ctv); if (timevalcmp(&aitv->it_value, &ctv, <)) timevalclear(&aitv->it_value); else @@ -736,28 +736,33 @@ kern_setitimer(struct thread *td, u_int { struct proc *p = td->td_proc; struct timeval ctv; + sbintime_t sbt, pr; if (aitv == NULL) return (kern_getitimer(td, which, oitv)); if (which > ITIMER_PROF) return (EINVAL); - if (itimerfix(&aitv->it_value)) + if (itimerfix(&aitv->it_value) || + aitv->it_value.tv_sec > INT32_MAX / 2) return (EINVAL); if (!timevalisset(&aitv->it_value)) timevalclear(&aitv->it_interval); - else if (itimerfix(&aitv->it_interval)) + else if (itimerfix(&aitv->it_interval) || + aitv->it_interval.tv_sec > INT32_MAX / 2) return (EINVAL); if (which == ITIMER_REAL) { PROC_LOCK(p); if (timevalisset(&p->p_realtimer.it_value)) callout_stop(&p->p_itcallout); - getmicrouptime(&ctv); + microuptime(&ctv); if (timevalisset(&aitv->it_value)) { - callout_reset(&p->p_itcallout, tvtohz(&aitv->it_value), - realitexpire, p); + pr = tvtosbt(aitv->it_value) >> tc_precexp; timevaladd(&aitv->it_value, &ctv); + sbt = tvtosbt(aitv->it_value); + callout_reset_sbt(&p->p_itcallout, sbt, pr, + realitexpire, p, C_ABSOLUTE); } *oitv = p->p_realtimer; p->p_realtimer = *aitv; @@ -793,7 +798,8 @@ void realitexpire(void *arg) { struct proc *p; - struct timeval ctv, ntv; + struct timeval ctv; + sbintime_t isbt; p = (struct proc *)arg; kern_psignal(p, SIGALRM); @@ -803,19 +809,17 @@ realitexpire(void *arg) wakeup(&p->p_itcallout); return; } - for (;;) { + isbt = tvtosbt(p->p_realtimer.it_interval); + if (isbt >= sbt_timethreshold) + getmicrouptime(&ctv); + else + microuptime(&ctv); + do { timevaladd(&p->p_realtimer.it_value, &p->p_realtimer.it_interval); - getmicrouptime(&ctv); - if (timevalcmp(&p->p_realtimer.it_value, &ctv, >)) { - ntv = p->p_realtimer.it_value; - timevalsub(&ntv, &ctv); - callout_reset(&p->p_itcallout, tvtohz(&ntv) - 1, - realitexpire, p); - return; - } - } - /*NOTREACHED*/ + } while (timevalcmp(&p->p_realtimer.it_value, &ctv, <=)); + callout_reset_sbt(&p->p_itcallout, tvtosbt(p->p_realtimer.it_value), + isbt >> tc_precexp, realitexpire, p, C_ABSOLUTE); } /* @@ -830,8 +834,9 @@ itimerfix(struct timeval *tv) if (tv->tv_sec < 0 || tv->tv_usec < 0 || tv->tv_usec >= 1000000) return (EINVAL); - if (tv->tv_sec == 0 && tv->tv_usec != 0 && tv->tv_usec < tick) - tv->tv_usec = tick; + if (tv->tv_sec == 0 && tv->tv_usec != 0 && + tv->tv_usec < (u_int)tick / 16) + tv->tv_usec = (u_int)tick / 16; return (0); }
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