@@ -259,21 +259,21 @@ static __always_inline bool steal_account_process_tick(void)
#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;
This is a note to let you know that I have just added a patch titled sched/cputime: Fix steal_account_process_tick() to always return jiffies to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue This patch is scheduled to be released in version 3.19.8-ckt18. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.19.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 95543c69e17d8ae9a2a73b11ec1e9a6d4af150bc Mon Sep 17 00:00:00 2001 From: Chris Friesen <cbf123@mail.usask.ca> Date: Sat, 5 Mar 2016 23:18:48 -0600 Subject: sched/cputime: Fix steal_account_process_tick() to always return jiffies 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 <chris.friesen@windriver.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/56DBBDB8.40305@mail.usask.ca Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- kernel/sched/cputime.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) -- 2.7.4