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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2018-07-06 15:06:15 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-07-16 00:16:29 +0200 |
| commit | af0fffd9300b97d8875aa745bc78e2f6fdb3c1f0 (patch) | |
| tree | cea49fd154fce8fb2b34bc06349950dcc40fe302 /kernel/sched/core.c | |
| parent | 45f5519ec55e75af3565dd737586d3b041834f71 (diff) | |
| download | linux-af0fffd9300b97d8875aa745bc78e2f6fdb3c1f0.tar.bz2 | |
sched/core: Remove get_cpu() from sched_fork()
get_cpu() disables preemption for the entire sched_fork() function.
This get_cpu() was introduced in commit:
dd41f596cda0 ("sched: cfs core code")
... which also invoked sched_balance_self() and this function
required preemption do be off.
Today, sched_balance_self() seems to be moved to ->task_fork callback
which is invoked while the ->pi_lock is held.
set_load_weight() could invoke reweight_task() which then via $callchain
might end up in smp_processor_id() but since `update_load' is false
this won't happen.
I didn't find any this_cpu*() or similar usage during the initialisation
of the task_struct.
The `cpu' value (from get_cpu()) is only used later in __set_task_cpu()
while the ->pi_lock lock is held.
Based on this it is possible to remove get_cpu() and use
smp_processor_id() for the `cpu' variable without breaking anything.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180706130615.g2ex2kmfu5kcvlq6@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/core.c')
| -rw-r--r-- | kernel/sched/core.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ba6bb805693a..c3cf7d992159 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2294,7 +2294,6 @@ static inline void init_schedstats(void) {} int sched_fork(unsigned long clone_flags, struct task_struct *p) { unsigned long flags; - int cpu = get_cpu(); __sched_fork(clone_flags, p); /* @@ -2330,14 +2329,12 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) p->sched_reset_on_fork = 0; } - if (dl_prio(p->prio)) { - put_cpu(); + if (dl_prio(p->prio)) return -EAGAIN; - } else if (rt_prio(p->prio)) { + else if (rt_prio(p->prio)) p->sched_class = &rt_sched_class; - } else { + else p->sched_class = &fair_sched_class; - } init_entity_runnable_average(&p->se); @@ -2353,7 +2350,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) * We're setting the CPU for the first time, we don't migrate, * so use __set_task_cpu(). */ - __set_task_cpu(p, cpu); + __set_task_cpu(p, smp_processor_id()); if (p->sched_class->task_fork) p->sched_class->task_fork(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); @@ -2370,8 +2367,6 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) plist_node_init(&p->pushable_tasks, MAX_PRIO); RB_CLEAR_NODE(&p->pushable_dl_tasks); #endif - - put_cpu(); return 0; } |