Date: Fri, 25 Sep 2015 13:03:58 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r288216 - head/sys/kern Message-ID: <201509251303.t8PD3wjh038618@repo.freebsd.org>
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Author: kib Date: Fri Sep 25 13:03:57 2015 New Revision: 288216 URL: https://svnweb.freebsd.org/changeset/base/288216 Log: Use per-cpu values for base and last in tc_cpu_ticks(). The values are updated lockess, different CPUs write its own view of timecounter state. The critical section is done for safety, callers of tc_cpu_ticks() are supposed to already enter critical section, or to own a spinlock. The change fixes sporadical reports of too high values reported for the (W)CPU on platforms that do not provide cpu ticker and use tc_cpu_ticks(), in particular, arm*. Diagnosed and reviewed by: jhb Sponsored by: The FreeBSD Foundation MFC after: 1 week Modified: head/sys/kern/kern_tc.c Modified: head/sys/kern/kern_tc.c ============================================================================== --- head/sys/kern/kern_tc.c Fri Sep 25 10:14:39 2015 (r288215) +++ head/sys/kern/kern_tc.c Fri Sep 25 13:03:57 2015 (r288216) @@ -1924,20 +1924,27 @@ SYSINIT(timecounter, SI_SUB_CLOCKS, SI_O static int cpu_tick_variable; static uint64_t cpu_tick_frequency; +static DPCPU_DEFINE(uint64_t, tc_cpu_ticks_base); +static DPCPU_DEFINE(unsigned, tc_cpu_ticks_last); + static uint64_t tc_cpu_ticks(void) { - static uint64_t base; - static unsigned last; - unsigned u; struct timecounter *tc; + uint64_t res, *base; + unsigned u, *last; + critical_enter(); + base = DPCPU_PTR(tc_cpu_ticks_base); + last = DPCPU_PTR(tc_cpu_ticks_last); tc = timehands->th_counter; u = tc->tc_get_timecount(tc) & tc->tc_counter_mask; - if (u < last) - base += (uint64_t)tc->tc_counter_mask + 1; - last = u; - return (u + base); + if (u < *last) + *base += (uint64_t)tc->tc_counter_mask + 1; + *last = u; + res = u + *base; + critical_exit(); + return (res); } void
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