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Subject[tip: sched/core] sched/cpuacct: Fix charge cpuacct.usage_sys
The following commit has been merged into the sched/core branch of tip:

Commit-ID: dbe9337109c2705f08e6a00392f991eb2d2570a5
Gitweb: https://git.kernel.org/tip/dbe9337109c2705f08e6a00392f991eb2d2570a5
Author: Muchun Song <songmuchun@bytedance.com>
AuthorDate: Mon, 20 Apr 2020 15:04:53 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 19 May 2020 20:34:14 +02:00

sched/cpuacct: Fix charge cpuacct.usage_sys

The user_mode(task_pt_regs(tsk)) always return true for
user thread, and false for kernel thread. So it means that
the cpuacct.usage_sys is the time that kernel thread uses
not the time that thread uses in the kernel mode. We can
try get_irq_regs() first, if it is NULL, then we can fall
back to task_pt_regs().

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200420070453.76815-1-songmuchun@bytedance.com
---
kernel/sched/cpuacct.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 6448b04..941c28c 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -5,6 +5,7 @@
* Based on the work by Paul Menage (menage@google.com) and Balbir Singh
* (balbir@in.ibm.com).
*/
+#include <asm/irq_regs.h>
#include "sched.h"

/* Time spent by the tasks of the CPU accounting group executing in ... */
@@ -339,7 +340,7 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime)
{
struct cpuacct *ca;
int index = CPUACCT_STAT_SYSTEM;
- struct pt_regs *regs = task_pt_regs(tsk);
+ struct pt_regs *regs = get_irq_regs() ? : task_pt_regs(tsk);

if (regs && user_mode(regs))
index = CPUACCT_STAT_USER;
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