Both callers of finish_task_switch() need to recalculate this_rq() and pass it as an argument, plus __schedule() does this again after context_switch().
It would be simpler to call this_rq() once in finish_task_switch() and return the this rq to the callers. Note: probably "int cpu" in __schedule() should die; it is not used and both rcu_note_context_switch() and wq_worker_sleeping() do not really need this argument. Signed-off-by: Oleg Nesterov <[email protected]> --- kernel/sched/core.c | 37 +++++++++++++++---------------------- 1 files changed, 15 insertions(+), 22 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index cfe9905..3bfbd3d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2200,10 +2200,16 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev, * so, we finish that here outside of the runqueue lock. (Doing it * with the lock held can cause deadlocks; see schedule() for * details.) + * + * The context switch have flipped the stack from under us and restored the + * local variables which were saved when this task called schedule() in the + * past. prev == current is still correct but we need to recalculate this_rq + * because prev may have moved to another CPU. */ -static void finish_task_switch(struct rq *rq, struct task_struct *prev) +static struct rq *finish_task_switch(struct task_struct *prev) __releases(rq->lock) { + struct rq *rq = this_rq(); struct mm_struct *mm = rq->prev_mm; long prev_state; @@ -2243,6 +2249,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev) } tick_nohz_task_switch(current); + return rq; } #ifdef CONFIG_SMP @@ -2281,8 +2288,7 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev) /* finish_task_switch() drops rq->lock and enables preemtion */ preempt_disable(); - rq = this_rq(); - finish_task_switch(rq, prev); + rq = finish_task_switch(prev); post_schedule(rq); preempt_enable(); @@ -2291,10 +2297,9 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev) } /* - * context_switch - switch to the new MM and the new - * thread's register state. + * context_switch - switch to the new MM and the new thread's register state. */ -static inline void +static inline struct rq * context_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) { @@ -2335,14 +2340,9 @@ context_switch(struct rq *rq, struct task_struct *prev, context_tracking_task_switch(prev, next); /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); - barrier(); - /* - * this_rq must be evaluated again because prev may have moved - * CPUs since it called schedule(), thus the 'rq' on its stack - * frame will be invalid. - */ - finish_task_switch(this_rq(), prev); + + return finish_task_switch(prev); } /* @@ -2802,15 +2802,8 @@ need_resched: rq->curr = next; ++*switch_count; - context_switch(rq, prev, next); /* unlocks the rq */ - /* - * The context switch have flipped the stack from under us - * and restored the local variables which were saved when - * this task called schedule() in the past. prev == current - * is still correct, but it can be moved to another cpu/rq. - */ - cpu = smp_processor_id(); - rq = cpu_rq(cpu); + rq = context_switch(rq, prev, next); /* unlocks the rq */ + cpu = rq->cpu; } else raw_spin_unlock_irq(&rq->lock); -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
