Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757441Ab0DFVa7 (ORCPT ); Tue, 6 Apr 2010 17:30:59 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:43019 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756836Ab0DFVay (ORCPT ); Tue, 6 Apr 2010 17:30:54 -0400 From: John Stultz To: lkml Cc: John Stultz , =?utf-8?q?Petr=20Tit=C4=9Bra?= , Thomas Gleixner Subject: [PATCH] time: remove xtime_cache (take 2) Date: Tue, 6 Apr 2010 14:30:51 -0700 Message-Id: <1270589451-30773-1-git-send-email-johnstul@us.ibm.com> X-Mailer: git-send-email 1.6.0.4 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5320 Lines: 170 Thomas: Mind queueing this up for 2.6.35? With the earlier logarithmic time accumulation patch, xtime will now always be within one "tick" of the current time, instead of possibly half a second off. This removes the need for the xtime_cache value, which always stored the time at the last interrupt, so this patch cleans that up removing the xtime_cache related code. This patch also addresses an issue with an earlier version of this change, where xtime_cache was normalizing xtime, which could in some cases be not valid (ie: tv_nsec == NSEC_PER_SEC). This is fixed by handling the edge case in update_wall_time(). Cc: Petr Titěra Cc: Thomas Gleixner Signed-off-by: John Stultz --- include/linux/time.h | 1 - kernel/time.c | 1 - kernel/time/timekeeping.c | 35 ++++++++++++++++------------------- 3 files changed, 16 insertions(+), 21 deletions(-) diff --git a/include/linux/time.h b/include/linux/time.h index 6e026e4..ea3559f 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -150,7 +150,6 @@ extern struct timespec timespec_trunc(struct timespec t, unsigned gran); extern int timekeeping_valid_for_hres(void); extern u64 timekeeping_max_deferment(void); extern void update_wall_time(void); -extern void update_xtime_cache(u64 nsec); extern void timekeeping_leap_insert(int leapsecond); struct tms; diff --git a/kernel/time.c b/kernel/time.c index 656dccf..129fe12 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -135,7 +135,6 @@ static inline void warp_clock(void) write_seqlock_irq(&xtime_lock); wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60; xtime.tv_sec += sys_tz.tz_minuteswest * 60; - update_xtime_cache(0); write_sequnlock_irq(&xtime_lock); clock_was_set(); } diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 39f6177..dec9175 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -165,13 +165,6 @@ struct timespec raw_time; /* flag for if timekeeping is suspended */ int __read_mostly timekeeping_suspended; -static struct timespec xtime_cache __attribute__ ((aligned (16))); -void update_xtime_cache(u64 nsec) -{ - xtime_cache = xtime; - timespec_add_ns(&xtime_cache, nsec); -} - /* must hold xtime_lock */ void timekeeping_leap_insert(int leapsecond) { @@ -332,8 +325,6 @@ int do_settimeofday(struct timespec *tv) xtime = *tv; - update_xtime_cache(0); - timekeeper.ntp_error = 0; ntp_clear(); @@ -559,7 +550,6 @@ void __init timekeeping_init(void) } set_normalized_timespec(&wall_to_monotonic, -boot.tv_sec, -boot.tv_nsec); - update_xtime_cache(0); total_sleep_time.tv_sec = 0; total_sleep_time.tv_nsec = 0; write_sequnlock_irqrestore(&xtime_lock, flags); @@ -593,7 +583,6 @@ static int timekeeping_resume(struct sys_device *dev) wall_to_monotonic = timespec_sub(wall_to_monotonic, ts); total_sleep_time = timespec_add_safe(total_sleep_time, ts); } - update_xtime_cache(0); /* re-base the last cycle value */ timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock); timekeeper.ntp_error = 0; @@ -788,7 +777,6 @@ void update_wall_time(void) { struct clocksource *clock; cycle_t offset; - u64 nsecs; int shift = 0, maxshift; /* Make sure we're fully resumed: */ @@ -847,7 +835,9 @@ void update_wall_time(void) timekeeper.ntp_error += neg << timekeeper.ntp_error_shift; } - /* store full nanoseconds into xtime after rounding it up and + + /* + * Store full nanoseconds into xtime after rounding it up and * add the remainder to the error difference. */ xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1; @@ -855,8 +845,15 @@ void update_wall_time(void) timekeeper.ntp_error += timekeeper.xtime_nsec << timekeeper.ntp_error_shift; - nsecs = clocksource_cyc2ns(offset, timekeeper.mult, timekeeper.shift); - update_xtime_cache(nsecs); + /* + * Finally, make sure that after the rounding + * xtime.tv_nsec isn't larger then NSEC_PER_SEC + */ + if (unlikely(xtime.tv_nsec >= NSEC_PER_SEC)) { + xtime.tv_nsec -= NSEC_PER_SEC; + xtime.tv_sec++; + second_overflow(); + } /* check to see if there is a new clocksource to use */ update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult); @@ -896,13 +893,13 @@ EXPORT_SYMBOL_GPL(monotonic_to_bootbased); unsigned long get_seconds(void) { - return xtime_cache.tv_sec; + return xtime.tv_sec; } EXPORT_SYMBOL(get_seconds); struct timespec __current_kernel_time(void) { - return xtime_cache; + return xtime; } struct timespec current_kernel_time(void) @@ -913,7 +910,7 @@ struct timespec current_kernel_time(void) do { seq = read_seqbegin(&xtime_lock); - now = xtime_cache; + now = xtime; } while (read_seqretry(&xtime_lock, seq)); return now; @@ -928,7 +925,7 @@ struct timespec get_monotonic_coarse(void) do { seq = read_seqbegin(&xtime_lock); - now = xtime_cache; + now = xtime; mono = wall_to_monotonic; } while (read_seqretry(&xtime_lock, seq)); -- 1.6.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/