Date: Mon, 16 Jul 2012 00:21:06 +0000 (UTC) From: Davide Italiano <davide@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r238512 - projects/calloutng/sys/kern Message-ID: <201207160021.q6G0L6U6087116@svn.freebsd.org>
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Author: davide Date: Mon Jul 16 00:21:05 2012 New Revision: 238512 URL: http://svn.freebsd.org/changeset/base/238512 Log: Refactor a comment in kern_clocksource.c to explain the need of an apparently duplicate check on event times. Modified: projects/calloutng/sys/kern/kern_clocksource.c Modified: projects/calloutng/sys/kern/kern_clocksource.c ============================================================================== --- projects/calloutng/sys/kern/kern_clocksource.c Mon Jul 16 00:14:25 2012 (r238511) +++ projects/calloutng/sys/kern/kern_clocksource.c Mon Jul 16 00:21:05 2012 (r238512) @@ -871,7 +871,13 @@ cpu_new_callout(int cpu, struct bintime state = DPCPU_ID_PTR(cpu, timerstate); ET_HW_LOCK(state); - /* If there is callout time already set earlier -- do nothing. */ + /* + * If there is callout time already set earlier -- do nothing. + * This check may appear redundant because we check already in + * callout_process() but this double check guarantees we're safe + * with respect to race conditions between interrupts execution + * and scheduling. + */ if (state->nextcall.sec != -1 && bintime_cmp(&bt, &state->nextcall, >=)) { ET_HW_UNLOCK(state);
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