The patch titled lockdep: re-annotate scheduler runqueues has been removed from the -mm tree. Its filename was lockdep-re-annotate-scheduler-runqueues.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: lockdep: re-annotate scheduler runqueues From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Instead of using a per-rq lock class, use the regular nesting operations. However, take extra care with double_lock_balance() as it can release the already held rq->lock (and therefore change its nesting class). So what can happen is: spin_lock(rq->lock); // this rq subclass 0 double_lock_balance(rq, other_rq); // release rq // acquire other_rq->lock subclass 0 // acquire rq->lock subclass 1 spin_unlock(other_rq->lock); leaving you with rq->lock in subclass 1 So a subsequent double_lock_balance() call can try to nest a subclass 1 lock while already holding a subclass 1 lock. Fix this by introducing double_unlock_balance() which releases the other rq's lock, but also re-sets the subclass for this rq's lock to 0. Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/sched.c | 21 +++++++++++++-------- kernel/sched_rt.c | 8 +++++--- 2 files changed, 18 insertions(+), 11 deletions(-) diff -puN kernel/sched.c~lockdep-re-annotate-scheduler-runqueues kernel/sched.c --- a/kernel/sched.c~lockdep-re-annotate-scheduler-runqueues +++ a/kernel/sched.c @@ -600,7 +600,6 @@ struct rq { /* BKL stats */ unsigned int bkl_count; #endif - struct lock_class_key rq_lock_key; }; static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); @@ -2756,10 +2755,10 @@ static void double_rq_lock(struct rq *rq } else { if (rq1 < rq2) { spin_lock(&rq1->lock); - spin_lock(&rq2->lock); + spin_lock_nested(&rq2->lock, SINGLE_DEPTH_NESTING); } else { spin_lock(&rq2->lock); - spin_lock(&rq1->lock); + spin_lock_nested(&rq1->lock, SINGLE_DEPTH_NESTING); } } update_rq_clock(rq1); @@ -2802,14 +2801,21 @@ static int double_lock_balance(struct rq if (busiest < this_rq) { spin_unlock(&this_rq->lock); spin_lock(&busiest->lock); - spin_lock(&this_rq->lock); + spin_lock_nested(&this_rq->lock, SINGLE_DEPTH_NESTING); ret = 1; } else - spin_lock(&busiest->lock); + spin_lock_nested(&busiest->lock, SINGLE_DEPTH_NESTING); } return ret; } +static void double_unlock_balance(struct rq *this_rq, struct rq *busiest) + __releases(busiest->lock) +{ + spin_unlock(&busiest->lock); + lock_set_subclass(&this_rq->lock.dep_map, 0, _RET_IP_); +} + /* * If dest_cpu is allowed for this process, migrate the task to it. * This is accomplished by forcing the cpu_allowed mask to only @@ -3634,7 +3640,7 @@ redo: ld_moved = move_tasks(this_rq, this_cpu, busiest, imbalance, sd, CPU_NEWLY_IDLE, &all_pinned); - spin_unlock(&busiest->lock); + double_unlock_balance(this_rq, busiest); if (unlikely(all_pinned)) { cpu_clear(cpu_of(busiest), *cpus); @@ -3749,7 +3755,7 @@ static void active_load_balance(struct r else schedstat_inc(sd, alb_failed); } - spin_unlock(&target_rq->lock); + double_unlock_balance(busiest_rq, target_rq); } #ifdef CONFIG_NO_HZ @@ -7987,7 +7993,6 @@ void __init sched_init(void) rq = cpu_rq(i); spin_lock_init(&rq->lock); - lockdep_set_class(&rq->lock, &rq->rq_lock_key); rq->nr_running = 0; init_cfs_rq(&rq->cfs, rq); init_rt_rq(&rq->rt, rq); diff -puN kernel/sched_rt.c~lockdep-re-annotate-scheduler-runqueues kernel/sched_rt.c --- a/kernel/sched_rt.c~lockdep-re-annotate-scheduler-runqueues +++ a/kernel/sched_rt.c @@ -861,6 +861,8 @@ static void put_prev_task_rt(struct rq * #define RT_MAX_TRIES 3 static int double_lock_balance(struct rq *this_rq, struct rq *busiest); +static void double_unlock_balance(struct rq *this_rq, struct rq *busiest); + static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep); static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) @@ -1022,7 +1024,7 @@ static struct rq *find_lock_lowest_rq(st break; /* try again */ - spin_unlock(&lowest_rq->lock); + double_unlock_balance(rq, lowest_rq); lowest_rq = NULL; } @@ -1091,7 +1093,7 @@ static int push_rt_task(struct rq *rq) resched_task(lowest_rq->curr); - spin_unlock(&lowest_rq->lock); + double_unlock_balance(rq, lowest_rq); ret = 1; out: @@ -1197,7 +1199,7 @@ static int pull_rt_task(struct rq *this_ } skip: - spin_unlock(&src_rq->lock); + double_unlock_balance(this_rq, src_rq); } return ret; _ Patches currently in -mm which might be from a.p.zijlstra@xxxxxxxxx are origin.patch linux-next.patch irq-warn-about-irqf_disabledirqf_shared.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html