diff options
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 50 | ||||
| -rw-r--r-- | kernel/sched/psi.c | 5 |
2 files changed, 48 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 09fd62568ba9..8471a0f7eb32 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5496,6 +5496,8 @@ static int _sched_setscheduler(struct task_struct *p, int policy, * @policy: new policy. * @param: structure containing the new RT priority. * + * Use sched_set_fifo(), read its comment. + * * Return: 0 on success. An error code otherwise. * * NOTE that the task may be already dead. @@ -5505,13 +5507,11 @@ int sched_setscheduler(struct task_struct *p, int policy, { return _sched_setscheduler(p, policy, param, true); } -EXPORT_SYMBOL_GPL(sched_setscheduler); int sched_setattr(struct task_struct *p, const struct sched_attr *attr) { return __sched_setscheduler(p, attr, true, true); } -EXPORT_SYMBOL_GPL(sched_setattr); int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr) { @@ -5536,7 +5536,51 @@ int sched_setscheduler_nocheck(struct task_struct *p, int policy, { return _sched_setscheduler(p, policy, param, false); } -EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck); + +/* + * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally + * incapable of resource management, which is the one thing an OS really should + * be doing. + * + * This is of course the reason it is limited to privileged users only. + * + * Worse still; it is fundamentally impossible to compose static priority + * workloads. You cannot take two correctly working static prio workloads + * and smash them together and still expect them to work. + * + * For this reason 'all' FIFO tasks the kernel creates are basically at: + * + * MAX_RT_PRIO / 2 + * + * The administrator _MUST_ configure the system, the kernel simply doesn't + * know enough information to make a sensible choice. + */ +void sched_set_fifo(struct task_struct *p) +{ + struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 }; + WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); +} +EXPORT_SYMBOL_GPL(sched_set_fifo); + +/* + * For when you don't much care about FIFO, but want to be above SCHED_NORMAL. + */ +void sched_set_fifo_low(struct task_struct *p) +{ + struct sched_param sp = { .sched_priority = 1 }; + WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); +} +EXPORT_SYMBOL_GPL(sched_set_fifo_low); + +void sched_set_normal(struct task_struct *p, int nice) +{ + struct sched_attr attr = { + .sched_policy = SCHED_NORMAL, + .sched_nice = nice, + }; + WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0); +} +EXPORT_SYMBOL_GPL(sched_set_normal); static int do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index e53b711bd643..967732c0766c 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -616,11 +616,8 @@ out: static int psi_poll_worker(void *data) { struct psi_group *group = (struct psi_group *)data; - struct sched_param param = { - .sched_priority = 1, - }; - sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m); + sched_set_fifo_low(current); while (true) { wait_event_interruptible(group->poll_wait, |