Does something like the below make sense to you guys?
---
Subject: sched: Move SCHED_RESET_ON_FORK into attr::sched_flags
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed Jan 15 17:05:04 CET 2014
I noticed the new sched_{set,get}attr() calls didn't properly deal
with the SCHED_RESET_ON_FORK hack.
Instead of propagating the flags in high bits nonsense use the brand
spanking new attr::sched_flags field.
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-h96ck1ivcs35jbpcnuwyu5fr@xxxxxxxxxxxxxx
---
include/uapi/linux/sched.h | 5 +++++
kernel/sched/core.c | 42 ++++++++++++++++++++++++++++--------------
2 files changed, 33 insertions(+), 14 deletions(-)
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -40,8 +40,13 @@
/* SCHED_ISO: reserved but not implemented yet */
#define SCHED_IDLE 5
#define SCHED_DEADLINE 6
+
/* Can be ORed in to make sure the process is reverted back to SCHED_NORMAL on fork */
#define SCHED_RESET_ON_FORK 0x40000000
+/*
+ * For the sched_{set,get}attr() calls
+ */
+#define SCHED_FLAG_RESET_ON_FORK 0x01
#endif /* _UAPI_LINUX_SCHED_H */
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3267,8 +3267,7 @@ static int __sched_setscheduler(struct t
reset_on_fork = p->sched_reset_on_fork;
policy = oldpolicy = p->policy;
} else {
- reset_on_fork = !!(policy & SCHED_RESET_ON_FORK);
- policy &= ~SCHED_RESET_ON_FORK;
+ reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
if (policy != SCHED_DEADLINE &&
policy != SCHED_FIFO && policy != SCHED_RR &&
@@ -3277,6 +3276,9 @@ static int __sched_setscheduler(struct t
return -EINVAL;
}
+ if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
+ return -EINVAL;
+
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
@@ -3444,6 +3446,26 @@ static int __sched_setscheduler(struct t
return 0;
}
+static int _sched_setscheduler(struct task_struct *p, int policy,
+ const struct sched_param *param, bool check)
+{
+ struct sched_attr attr = {
+ .sched_policy = policy,
+ .sched_priority = param->sched_priority,
+ .sched_nice = PRIO_TO_NICE(p->static_prio),
+ };
+
+ /*
+ * Fixup the legacy SCHED_RESET_ON_FORK hack
+ */
+ if (policy & SCHED_RESET_ON_FORK) {
+ attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+ policy &= ~SCHED_RESET_ON_FORK;
+ attr.sched_policy = policy;
+ }
+
+ return __sched_setscheduler(p, &attr, check);
+}
/**
* sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
* @p: the task in question.
@@ -3457,12 +3479,7 @@ static int __sched_setscheduler(struct t
int sched_setscheduler(struct task_struct *p, int policy,
const struct sched_param *param)
{
- struct sched_attr attr = {
- .sched_policy = policy,
- .sched_priority = param->sched_priority,
- .sched_nice = PRIO_TO_NICE(p->static_prio),
- };
- return __sched_setscheduler(p, &attr, true);
+ return _sched_setscheduler(p, policy, param, true);
}
EXPORT_SYMBOL_GPL(sched_setscheduler);
@@ -3488,12 +3505,7 @@ EXPORT_SYMBOL_GPL(sched_setattr);
int sched_setscheduler_nocheck(struct task_struct *p, int policy,
const struct sched_param *param)
{
- struct sched_attr attr = {
- .sched_policy = policy,
- .sched_priority = param->sched_priority,
- .sched_nice = PRIO_TO_NICE(p->static_prio),
- };
- return __sched_setscheduler(p, &attr, false);
+ return _sched_setscheduler(p, policy, param, false);
}
static int
@@ -3793,6 +3805,8 @@ SYSCALL_DEFINE3(sched_getattr, pid_t, pi
goto out_unlock;
attr.sched_policy = p->policy;
+ if (p->sched_reset_on_fork)
+ attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
if (task_has_dl_policy(p))
__getparam_dl(p, &attr);
else if (task_has_rt_policy(p))
--
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