Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752575AbaF1Knz (ORCPT ); Sat, 28 Jun 2014 06:43:55 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:50653 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752450AbaF1Knr (ORCPT ); Sat, 28 Jun 2014 06:43:47 -0400 From: Xie XiuQi To: CC: , , , , Subject: [PATCH 1/2] tracing: fix uptime overflow problem Date: Sat, 28 Jun 2014 19:10:00 +0800 Message-ID: <1403953801-19068-2-git-send-email-xiexiuqi@huawei.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1403953801-19068-1-git-send-email-xiexiuqi@huawei.com> References: <1403953801-19068-1-git-send-email-xiexiuqi@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The "uptime" tracer added in: commit 8aacf017b065a805d27467843490c976835eb4a5 tracing: Add "uptime" trace clock that uses jiffies has wraparound problems when the system has been up more than 1 hour 11 minutes and 34 seconds. It converts jiffies to nanoseconds using: (u64)jiffies_to_usecs(jiffy) * 1000ULL but since jiffies_to_usecs() only returns a 32-bit value, it truncates at 2^32 microseconds. An additional problem on 32-bit systems is that the argument is "unsigned long", so fixing the return value only helps until 2^32 jiffies (49.7 days on a HZ=1000 system). Tony provide full featured jiffies_to_nsecs() function, but can't resolve another problem that jiffies_lock is not safe in NMI context. Now we use the lockless function __current_kernel_time() and getboottime() to calculate the uptime. The former discussion is here: http://lkml.org/lkml/2014/4/8/525 Additional, I changed trace_clock_jiffies to trace_clock_uptime, in order to better describe its function. Reported-by: Tony Luck Cc: Tony Luck Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: stable@vger.kernel.org # 3.10+ Signed-off-by: Xie XiuQi --- include/linux/trace_clock.h | 2 +- kernel/trace/trace.c | 2 +- kernel/trace/trace_clock.c | 15 +++++++++++---- 3 files changed, 13 insertions(+), 6 deletions(-) diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h index 1d7ca27..2961ac7 100644 --- a/include/linux/trace_clock.h +++ b/include/linux/trace_clock.h @@ -16,7 +16,7 @@ extern u64 notrace trace_clock_local(void); extern u64 notrace trace_clock(void); -extern u64 notrace trace_clock_jiffies(void); +extern u64 notrace trace_clock_uptime(void); extern u64 notrace trace_clock_global(void); extern u64 notrace trace_clock_counter(void); diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 384ede3..867e849 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -809,7 +809,7 @@ static struct { { trace_clock_local, "local", 1 }, { trace_clock_global, "global", 1 }, { trace_clock_counter, "counter", 0 }, - { trace_clock_jiffies, "uptime", 1 }, + { trace_clock_uptime, "uptime", 1 }, { trace_clock, "perf", 1 }, ARCH_TRACE_CLOCKS }; diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c index 26dc348..59e4d4d 100644 --- a/kernel/trace/trace_clock.c +++ b/kernel/trace/trace_clock.c @@ -19,6 +19,7 @@ #include #include #include +#include #include /* @@ -58,14 +59,20 @@ u64 notrace trace_clock(void) } /* - * trace_jiffy_clock(): Simply use jiffies as a clock counter. + * trace_clock_uptime(): Use lockless version __current_kernel_time, + * so it's safe in NMI context. */ -u64 notrace trace_clock_jiffies(void) +u64 notrace trace_clock_uptime(void) { - u64 jiffy = jiffies - INITIAL_JIFFIES; + struct timespec uptime, now, boottime; + + /* Does not take xtime_lock, so it's safe in NMI context. */ + now = __current_kernel_time(); + getboottime(&boottime); + uptime = timespec_sub(now, boottime); /* Return nsecs */ - return (u64)jiffies_to_usecs(jiffy) * 1000ULL; + return timespec_to_ns(&uptime); } /* -- 2.0.0 -- 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/