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sched/core: Allow sched_setattr() to use the current policy 

The sched_setattr() syscall mandates that a policy is always specified.
This requires to always know which policy a task will have when
attributes are configured and this makes it impossible to add more
generic task attributes valid across different scheduling policies.
Reading the policy before setting generic tasks attributes is racy since
we cannot be sure it is not changed concurrently.

Introduce the required support to change generic task attributes without
affecting the current task policy. This is done by adding an attribute flag
(SCHED_FLAG_KEEP_POLICY) to enforce the usage of the current policy.

Add support for the SETPARAM_POLICY policy, which is already used by the
sched_setparam() POSIX syscall, to the sched_setattr() non-POSIX
syscall.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alessio Balsini <balsini@android.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Perret <quentin.perret@arm.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Steve Muckle <smuckle@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@google.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lkml.kernel.org/r/20190621084217.8167-6-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Patrick Bellasi 2019-06-21 09:42:06 +01:00 committed by Ingo Molnar
parent e8f14172c6
commit 1d6362fa0c
2 changed files with 5 additions and 1 deletions
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4
include/uapi/linux/sched.h
View File

@ -51,9 +51,11 @@
#define SCHED_FLAG_RESET_ON_FORK 0x01
#define SCHED_FLAG_RECLAIM 0x02
#define SCHED_FLAG_DL_OVERRUN 0x04
#define SCHED_FLAG_KEEP_POLICY 0x08
#define SCHED_FLAG_ALL (SCHED_FLAG_RESET_ON_FORK | \
SCHED_FLAG_RECLAIM | \
SCHED_FLAG_DL_OVERRUN)
SCHED_FLAG_DL_OVERRUN | \
SCHED_FLAG_KEEP_POLICY)
#endif /* _UAPI_LINUX_SCHED_H */

2
kernel/sched/core.c
View File

@ -4897,6 +4897,8 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
if ((int)attr.sched_policy < 0)
return -EINVAL;
if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
attr.sched_policy = SETPARAM_POLICY;
rcu_read_lock();
retval = -ESRCH;