Messages in this thread Patch in this message | | | Date | Thu, 29 Jul 2021 18:52:13 +0100 | Subject | [PATCH v2] sched/deadline: Fix sched_getattr() for DL tasks | From | Quentin Perret <> |
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In its current state, sched_getattr() can report incorrect sched_flags if called on a deadline task.
Firstly, if the reset_on_fork flag is set on a deadline task using sched_setattr() with SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS, p->sched_reset_on_fork will be set but __setscheduler() will bail out early without updating the dl_se->flags. Consequently, if sched_getattr is then called on the same task, __getparam_dl() will override kattr.sched_flags with the now out-of-date copy in dl_se->flags and report a stale reset_on_fork value to userspace.
And secondly, sched_getattr() currently reports SCHED_FLAG_SUGOV as set if called on a schedutil worker, despite this flag being a kernel-only value that is not exposed in UAPI headers.
To fix both of these problems, make sure to only copy the flags that are relevant to sched_deadline to dl_se->flags, and filter them out when reporting them back to userspace.
Signed-off-by: Quentin Perret <qperret@google.com> --- v1 can be found here: https://lore.kernel.org/r/20210727101103.2729607-1-qperret@google.com/
Changes since v1: - squashed the two patches together - moved the SCHED_FLAG_SUGOV filtering to __getparam_dl() --- 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..358a8a2acfc2 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 & ~SCHED_FLAG_SUGOV; } /* @@ -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 -- 2.32.0.554.ge1b32706d8-goog
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