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authorJuri Lelli <juri.lelli@arm.com>2014-10-07 09:52:11 +0100
committerIngo Molnar <mingo@kernel.org>2014-10-28 10:48:00 +0100
commitf82f80426f7afcf55953924e71555984a4bd6ce6 (patch)
tree3a3e15c85f04c11d8f9bc0708b4c8ca439d3431b
parent7f51412a415d87ea8598d14722fb31e4f5701257 (diff)
downloadop-kernel-dev-f82f80426f7afcf55953924e71555984a4bd6ce6.zip
op-kernel-dev-f82f80426f7afcf55953924e71555984a4bd6ce6.tar.gz
sched/deadline: Ensure that updates to exclusive cpusets don't break AC
How we deal with updates to exclusive cpusets is currently broken. As an example, suppose we have an exclusive cpuset composed of two cpus: A[cpu0,cpu1]. We can assign SCHED_DEADLINE task to it up to the allowed bandwidth. If we want now to modify cpusetA's cpumask, we have to check that removing a cpu's amount of bandwidth doesn't break AC guarantees. This thing isn't checked in the current code. This patch fixes the problem above, denying an update if the new cpumask won't have enough bandwidth for SCHED_DEADLINE tasks that are currently active. Signed-off-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Li Zefan <lizefan@huawei.com> Cc: cgroups@vger.kernel.org Link: http://lkml.kernel.org/r/5433E6AF.5080105@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/linux/sched.h2
-rw-r--r--kernel/cpuset.c10
-rw-r--r--kernel/sched/core.c19
3 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1d1fa08..320a977 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2052,6 +2052,8 @@ static inline void tsk_restore_flags(struct task_struct *task,
task->flags |= orig_flags & flags;
}
+extern int cpuset_cpumask_can_shrink(const struct cpumask *cur,
+ const struct cpumask *trial);
extern int task_can_attach(struct task_struct *p,
const struct cpumask *cs_cpus_allowed);
#ifdef CONFIG_SMP
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 7af8577..723cfc9 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -506,6 +506,16 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
goto out;
}
+ /*
+ * We can't shrink if we won't have enough room for SCHED_DEADLINE
+ * tasks.
+ */
+ ret = -EBUSY;
+ if (is_cpu_exclusive(cur) &&
+ !cpuset_cpumask_can_shrink(cur->cpus_allowed,
+ trial->cpus_allowed))
+ goto out;
+
ret = 0;
out:
rcu_read_unlock();
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9993fee..0456a55 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4650,6 +4650,25 @@ void init_idle(struct task_struct *idle, int cpu)
#endif
}
+int cpuset_cpumask_can_shrink(const struct cpumask *cur,
+ const struct cpumask *trial)
+{
+ int ret = 1, trial_cpus;
+ struct dl_bw *cur_dl_b;
+ unsigned long flags;
+
+ cur_dl_b = dl_bw_of(cpumask_any(cur));
+ trial_cpus = cpumask_weight(trial);
+
+ raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
+ if (cur_dl_b->bw != -1 &&
+ cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
+ ret = 0;
+ raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
+
+ return ret;
+}
+
int task_can_attach(struct task_struct *p,
const struct cpumask *cs_cpus_allowed)
{
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