From: Quentin Perret <qperret@google.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
linux-kernel@vger.kernel.org
Cc: Quentin Perret <qperret@google.com>
Subject: [PATCH 1/2] sched/deadline: Fix reset_on_fork reporting of DL tasks
Date: Tue, 27 Jul 2021 11:11:01 +0100 [thread overview]
Message-ID: <20210727101103.2729607-2-qperret@google.com> (raw)
In-Reply-To: <20210727101103.2729607-1-qperret@google.com>
It is possible for sched_getattr() to incorrectly report the state of
the reset_on_fork flag when called on a deadline task.
Indeed, if the flag was set on a deadline task using sched_setattr()
with flags (SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS), then
p->sched_reset_on_fork will be set, but __setscheduler() will bail out
early, which means that the dl_se->flags will not get updated by
__setscheduler_params()->__setparam_dl(). Consequently, if
sched_getattr() is then called on the task, __getparam_dl() will
override kattr.sched_flags with the now out-of-date copy in dl_se->flags
and report the stale value to userspace.
To fix this, make sure to only copy the flags that are relevant to
sched_deadline to and from the dl_se->flags field.
Signed-off-by: Quentin Perret <qperret@google.com>
---
kernel/sched/deadline.c | 7 ++++---
kernel/sched/sched.h | 2 ++
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index aaacd6cfd42f..5cafc642e647 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2741,7 +2741,7 @@ void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
dl_se->dl_runtime = attr->sched_runtime;
dl_se->dl_deadline = attr->sched_deadline;
dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
- dl_se->flags = attr->sched_flags;
+ dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS;
dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
}
@@ -2754,7 +2754,8 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
attr->sched_runtime = dl_se->dl_runtime;
attr->sched_deadline = dl_se->dl_deadline;
attr->sched_period = dl_se->dl_period;
- attr->sched_flags = dl_se->flags;
+ attr->sched_flags &= ~SCHED_DL_FLAGS;
+ attr->sched_flags |= dl_se->flags;
}
/*
@@ -2851,7 +2852,7 @@ bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
if (dl_se->dl_runtime != attr->sched_runtime ||
dl_se->dl_deadline != attr->sched_deadline ||
dl_se->dl_period != attr->sched_period ||
- dl_se->flags != attr->sched_flags)
+ dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS))
return true;
return false;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 14a41a243f7b..ad3aee63db26 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -227,6 +227,8 @@ static inline void update_avg(u64 *avg, u64 sample)
*/
#define SCHED_FLAG_SUGOV 0x10000000
+#define SCHED_DL_FLAGS (SCHED_FLAG_RECLAIM | SCHED_FLAG_DL_OVERRUN | SCHED_FLAG_SUGOV)
+
static inline bool dl_entity_is_special(struct sched_dl_entity *dl_se)
{
#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
--
2.32.0.432.gabb21c7263-goog
next prev parent reply other threads:[~2021-07-27 10:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 10:11 [PATCH 0/2] A couple of sched_getattr() fixes for DL Quentin Perret
2021-07-27 10:11 ` Quentin Perret [this message]
2021-07-29 16:26 ` [PATCH 1/2] sched/deadline: Fix reset_on_fork reporting of DL tasks Dietmar Eggemann
2021-08-05 9:34 ` [tip: sched/core] " tip-bot2 for Quentin Perret
2021-07-27 10:11 ` [PATCH 2/2] sched: Don't report SCHED_FLAG_SUGOV in sched_getattr() Quentin Perret
2021-07-28 9:12 ` Juri Lelli
2021-07-28 9:39 ` Quentin Perret
2021-07-28 12:36 ` Juri Lelli
2021-07-29 17:21 ` Dietmar Eggemann
2021-07-29 17:28 ` Quentin Perret
2021-08-05 9:34 ` [tip: sched/core] " tip-bot2 for Quentin Perret
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