From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:35960 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759045AbcDISdJ (ORCPT ); Sat, 9 Apr 2016 14:33:09 -0400 Subject: Patch "sched/cputime: Fix steal_account_process_tick() to always return jiffies" has been added to the 4.5-stable tree To: cbf123@mail.usask.ca, chris.friesen@windriver.com, fweisbec@gmail.com, gregkh@linuxfoundation.org, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: , From: Date: Sat, 09 Apr 2016 11:33:08 -0700 Message-ID: <1460226788255209@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled sched/cputime: Fix steal_account_process_tick() to always return jiffies to the 4.5-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sched-cputime-fix-steal_account_process_tick-to-always-return-jiffies.patch and it can be found in the queue-4.5 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From f9c904b7613b8b4c85b10cd6b33ad41b2843fa9d Mon Sep 17 00:00:00 2001 From: Chris Friesen Date: Sat, 5 Mar 2016 23:18:48 -0600 Subject: sched/cputime: Fix steal_account_process_tick() to always return jiffies From: Chris Friesen commit f9c904b7613b8b4c85b10cd6b33ad41b2843fa9d upstream. The callers of steal_account_process_tick() expect it to return whether a jiffy should be considered stolen or not. Currently the return value of steal_account_process_tick() is in units of cputime, which vary between either jiffies or nsecs depending on CONFIG_VIRT_CPU_ACCOUNTING_GEN. If cputime has nsecs granularity and there is a tiny amount of stolen time (a few nsecs, say) then we will consider the entire tick stolen and will not account the tick on user/system/idle, causing /proc/stats to show invalid data. The fix is to change steal_account_process_tick() to accumulate the stolen time and only account it once it's worth a jiffy. (Thanks to Frederic Weisbecker for suggestions to fix a bug in my first version of the patch.) Signed-off-by: Chris Friesen Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/56DBBDB8.40305@mail.usask.ca Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/sched/cputime.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -262,21 +262,21 @@ static __always_inline bool steal_accoun #ifdef CONFIG_PARAVIRT if (static_key_false(¶virt_steal_enabled)) { u64 steal; - cputime_t steal_ct; + unsigned long steal_jiffies; steal = paravirt_steal_clock(smp_processor_id()); steal -= this_rq()->prev_steal_time; /* - * cputime_t may be less precise than nsecs (eg: if it's - * based on jiffies). Lets cast the result to cputime + * steal is in nsecs but our caller is expecting steal + * time in jiffies. Lets cast the result to jiffies * granularity and account the rest on the next rounds. */ - steal_ct = nsecs_to_cputime(steal); - this_rq()->prev_steal_time += cputime_to_nsecs(steal_ct); + steal_jiffies = nsecs_to_jiffies(steal); + this_rq()->prev_steal_time += jiffies_to_nsecs(steal_jiffies); - account_steal_time(steal_ct); - return steal_ct; + account_steal_time(jiffies_to_cputime(steal_jiffies)); + return steal_jiffies; } #endif return false; Patches currently in stable-queue which might be from cbf123@mail.usask.ca are queue-4.5/sched-cputime-fix-steal_account_process_tick-to-always-return-jiffies.patch