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SubjectRe: [PATCH 01/13] sched: Add 3 new scheduler syscalls to support an extended scheduling parameters ABI
On Fri, Feb 14, 2014 at 03:13:22PM +0100, Michael Kerrisk (man-pages) wrote:
> Peter, Dario,
>
> This is a little late in the day, but I think it's an important point
> to just check before this API goes final.
>
> > SYNOPSIS
> > #include <sched.h>
> >
> > struct sched_attr {
> > u32 size;
> >
> > u32 sched_policy;
> > u64 sched_flags;
> [...]
> > };
> >
> > int sched_setattr(pid_t pid, const struct sched_attr *attr);
> >
> > int sched_getattr(pid_t pid, const struct sched_attr *attr, unsigned int size);
>
> So, I that there's a flags field in the structure, which allows for
> some extensibility for these calls in the future. However, is it
> worthwhile to consider adding a 'flags' argument in the base signature
> of either of these calls, to allow for some possible extensions in the
> future. (See http://lwn.net/SubscriberLink/585415/7b905c0248a158a2/ ).

Sure why not.. I picked 'unsigned long' for the flags argument; I don't
think there's a real standard for this, I've seen: 'int' 'unsigned int'
and 'unsigned long' flags.

Please holler if there is indeed a preference and I picked the wrong
one.

BTW; do you need more text on the manpage thingy I send you or was that
sufficient?

---
Subject: sched: Add 'flags' argument to sched_{set,get}attr() syscalls

Because of a recent syscall design debate; its deemed appropriate for
each syscall to have a flags argument for future extension; without
immediately requiring new syscalls.

Suggested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
include/linux/syscalls.h | 6 ++++--
kernel/sched/core.c | 11 ++++++-----
2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 40ed9e9a77e5..bf41aeb09078 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -281,13 +281,15 @@ asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
asmlinkage long sys_sched_setparam(pid_t pid,
struct sched_param __user *param);
asmlinkage long sys_sched_setattr(pid_t pid,
- struct sched_attr __user *attr);
+ struct sched_attr __user *attr,
+ unsigned long flags);
asmlinkage long sys_sched_getscheduler(pid_t pid);
asmlinkage long sys_sched_getparam(pid_t pid,
struct sched_param __user *param);
asmlinkage long sys_sched_getattr(pid_t pid,
struct sched_attr __user *attr,
- unsigned int size);
+ unsigned int size,
+ unsigned long flags);
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr);
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fb9764fbc537..deeaa54fdf92 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3631,13 +3631,14 @@ SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
* @pid: the pid in question.
* @uattr: structure containing the extended parameters.
*/
-SYSCALL_DEFINE2(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr)
+SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
+ unsigned long, flags)
{
struct sched_attr attr;
struct task_struct *p;
int retval;

- if (!uattr || pid < 0)
+ if (!uattr || pid < 0 || flags)
return -EINVAL;

if (sched_copy_attr(uattr, &attr))
@@ -3774,8 +3775,8 @@ static int sched_read_attr(struct sched_attr __user *uattr,
* @uattr: structure containing the extended parameters.
* @size: sizeof(attr) for fwd/bwd comp.
*/
-SYSCALL_DEFINE3(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
- unsigned int, size)
+SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
+ unsigned int, size, unsigned long, flags)
{
struct sched_attr attr = {
.size = sizeof(struct sched_attr),
@@ -3784,7 +3785,7 @@ SYSCALL_DEFINE3(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
int retval;

if (!uattr || pid < 0 || size > PAGE_SIZE ||
- size < SCHED_ATTR_SIZE_VER0)
+ size < SCHED_ATTR_SIZE_VER0 || flags)
return -EINVAL;

rcu_read_lock();

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