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Message-ID: <163845435389.11128.15096993127413247810.tip-bot2@tip-bot2>
Date: Thu, 02 Dec 2021 14:12:33 -0000
From: "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Hasegawa Hitomi <hasegawa-hitomi@...itsu.com>,
Frederic Weisbecker <frederic@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Masayoshi Mizuma <m.mizuma@...fujitsu.com>,
Phil Auld <pauld@...hat.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: sched/urgent] sched/cputime: Fix getrusage(RUSAGE_THREAD) with
nohz_full
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: e7f2be115f0746b969c0df14c0d182f65f005ca5
Gitweb: https://git.kernel.org/tip/e7f2be115f0746b969c0df14c0d182f65f005ca5
Author: Frederic Weisbecker <frederic@...nel.org>
AuthorDate: Tue, 26 Oct 2021 16:10:55 +02:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 02 Dec 2021 15:08:22 +01:00
sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.
task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.
To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.
Reported-by: Hasegawa Hitomi <hasegawa-hitomi@...itsu.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@...itsu.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
Acked-by: Phil Auld <pauld@...hat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
---
include/linux/sched/cputime.h | 5 +++--
kernel/sched/cputime.c | 12 +++++++++---
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h
index 6c9f19a..ce3c582 100644
--- a/include/linux/sched/cputime.h
+++ b/include/linux/sched/cputime.h
@@ -18,15 +18,16 @@
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
-extern void task_cputime(struct task_struct *t,
+extern bool task_cputime(struct task_struct *t,
u64 *utime, u64 *stime);
extern u64 task_gtime(struct task_struct *t);
#else
-static inline void task_cputime(struct task_struct *t,
+static inline bool task_cputime(struct task_struct *t,
u64 *utime, u64 *stime)
{
*utime = t->utime;
*stime = t->stime;
+ return false;
}
static inline u64 task_gtime(struct task_struct *t)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 872e481..9392aea 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -615,7 +615,8 @@ void task_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
.sum_exec_runtime = p->se.sum_exec_runtime,
};
- task_cputime(p, &cputime.utime, &cputime.stime);
+ if (task_cputime(p, &cputime.utime, &cputime.stime))
+ cputime.sum_exec_runtime = task_sched_runtime(p);
cputime_adjust(&cputime, &p->prev_cputime, ut, st);
}
EXPORT_SYMBOL_GPL(task_cputime_adjusted);
@@ -828,19 +829,21 @@ u64 task_gtime(struct task_struct *t)
* add up the pending nohz execution time since the last
* cputime snapshot.
*/
-void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
+bool task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
{
struct vtime *vtime = &t->vtime;
unsigned int seq;
u64 delta;
+ int ret;
if (!vtime_accounting_enabled()) {
*utime = t->utime;
*stime = t->stime;
- return;
+ return false;
}
do {
+ ret = false;
seq = read_seqcount_begin(&vtime->seqcount);
*utime = t->utime;
@@ -850,6 +853,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
if (vtime->state < VTIME_SYS)
continue;
+ ret = true;
delta = vtime_delta(vtime);
/*
@@ -861,6 +865,8 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
else
*utime += vtime->utime + delta;
} while (read_seqcount_retry(&vtime->seqcount, seq));
+
+ return ret;
}
static int vtime_state_fetch(struct vtime *vtime, int cpu)
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