From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756036Ab1KOEE6 (ORCPT ); Mon, 14 Nov 2011 23:04:58 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:38906 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755811Ab1KOEEy (ORCPT ); Mon, 14 Nov 2011 23:04:54 -0500 From: John Stultz To: LKML Cc: John Stultz , Thomas Gleixner , Eric Dumazet , Richard Cochran Subject: [PATCH 09/16] ntp: Add ntp_lock to replace xtime_locking Date: Mon, 14 Nov 2011 20:03:59 -0800 Message-Id: <1321329846-14755-10-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.3.2.146.gca209 In-Reply-To: <1321329846-14755-1-git-send-email-john.stultz@linaro.org> References: <1321329846-14755-1-git-send-email-john.stultz@linaro.org> x-cbid: 11111504-1976-0000-0000-0000037F03CB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use a ntp_lock seqlock to replace xtime_lock locking in ntp.c CC: Thomas Gleixner CC: Eric Dumazet CC: Richard Cochran Signed-off-by: John Stultz --- kernel/time/ntp.c | 63 +++++++++++++++++++++++++++++++++++++---------------- 1 files changed, 44 insertions(+), 19 deletions(-) diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index f131ba6..a0756b3 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -22,6 +22,9 @@ * NTP timekeeping variables: */ +DEFINE_SEQLOCK(ntp_lock); + + /* USER_HZ period (usecs): */ unsigned long tick_usec = TICK_USEC; @@ -133,7 +136,7 @@ static inline void pps_reset_freq_interval(void) /** * pps_clear - Clears the PPS state variables * - * Must be called while holding a write on the xtime_lock + * Must be called while holding a write on the ntp_lock */ static inline void pps_clear(void) { @@ -149,7 +152,7 @@ static inline void pps_clear(void) * the last PPS signal. When it reaches 0, indicate that PPS signal is * missing. * - * Must be called while holding a write on the xtime_lock + * Must be called while holding a write on the ntp_lock */ static inline void pps_dec_valid(void) { @@ -341,11 +344,13 @@ static void ntp_update_offset(long offset) /** * ntp_clear - Clears the NTP state variables - * - * Must be called while holding a write on the xtime_lock */ void ntp_clear(void) { + unsigned long flags; + + write_seqlock_irqsave(&ntp_lock, flags); + time_adjust = 0; /* stop active adjtime() */ time_status |= STA_UNSYNC; time_maxerror = NTP_PHASE_LIMIT; @@ -358,12 +363,21 @@ void ntp_clear(void) /* Clear PPS state variables */ pps_clear(); + write_sequnlock_irqrestore(&ntp_lock, flags); + } u64 ntp_tick_length(void) { - return tick_length; + unsigned long seq; + s64 ret; + + do { + seq = read_seqbegin(&ntp_lock); + ret = tick_length; + } while (read_seqretry(&ntp_lock, seq)); + return ret; } @@ -375,14 +389,14 @@ u64 ntp_tick_length(void) static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) { enum hrtimer_restart res = HRTIMER_NORESTART; + int leap = 0; - write_seqlock(&xtime_lock); - + write_seqlock(&ntp_lock); switch (time_state) { case TIME_OK: break; case TIME_INS: - timekeeping_leap_insert(-1); + leap = -1; time_state = TIME_OOP; printk(KERN_NOTICE "Clock: inserting leap second 23:59:60 UTC\n"); @@ -390,7 +404,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) res = HRTIMER_RESTART; break; case TIME_DEL: - timekeeping_leap_insert(1); + leap = 1; time_tai--; time_state = TIME_WAIT; printk(KERN_NOTICE @@ -405,8 +419,14 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) time_state = TIME_OK; break; } + write_sequnlock(&ntp_lock); - write_sequnlock(&xtime_lock); + /* + * We have to call this outside of the ntp_lock to keep + * the proper locking hierarchy + */ + if (leap) + timekeeping_leap_insert(leap); return res; } @@ -422,6 +442,9 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) void second_overflow(void) { s64 delta; + unsigned long flags; + + write_seqlock_irqsave(&ntp_lock, flags); /* Bump the maxerror field */ time_maxerror += MAXFREQ / NSEC_PER_USEC; @@ -441,23 +464,25 @@ void second_overflow(void) pps_dec_valid(); if (!time_adjust) - return; + goto out; if (time_adjust > MAX_TICKADJ) { time_adjust -= MAX_TICKADJ; tick_length += MAX_TICKADJ_SCALED; - return; + goto out; } if (time_adjust < -MAX_TICKADJ) { time_adjust += MAX_TICKADJ; tick_length -= MAX_TICKADJ_SCALED; - return; + goto out; } tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT; time_adjust = 0; +out: + write_sequnlock_irqrestore(&ntp_lock, flags); } #ifdef CONFIG_GENERIC_CMOS_UPDATE @@ -681,7 +706,7 @@ int do_adjtimex(struct timex *txc) getnstimeofday(&ts); - write_seqlock_irq(&xtime_lock); + write_seqlock_irq(&ntp_lock); if (txc->modes & ADJ_ADJTIME) { long save_adjust = time_adjust; @@ -723,7 +748,7 @@ int do_adjtimex(struct timex *txc) /* fill PPS status fields */ pps_fill_timex(txc); - write_sequnlock_irq(&xtime_lock); + write_sequnlock_irq(&ntp_lock); txc->time.tv_sec = ts.tv_sec; txc->time.tv_usec = ts.tv_nsec; @@ -921,7 +946,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) pts_norm = pps_normalize_ts(*phase_ts); - write_seqlock_irqsave(&xtime_lock, flags); + write_seqlock_irqsave(&ntp_lock, flags); /* clear the error bits, they will be set again if needed */ time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); @@ -934,7 +959,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) * just start the frequency interval */ if (unlikely(pps_fbase.tv_sec == 0)) { pps_fbase = *raw_ts; - write_sequnlock_irqrestore(&xtime_lock, flags); + write_sequnlock_irqrestore(&ntp_lock, flags); return; } @@ -949,7 +974,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) time_status |= STA_PPSJITTER; /* restart the frequency calibration interval */ pps_fbase = *raw_ts; - write_sequnlock_irqrestore(&xtime_lock, flags); + write_sequnlock_irqrestore(&ntp_lock, flags); pr_err("hardpps: PPSJITTER: bad pulse\n"); return; } @@ -966,7 +991,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) hardpps_update_phase(pts_norm.nsec); - write_sequnlock_irqrestore(&xtime_lock, flags); + write_sequnlock_irqrestore(&ntp_lock, flags); } EXPORT_SYMBOL(hardpps); -- 1.7.3.2.146.gca209