Messages in this thread Patch in this message | | | Subject | Re: [BUG -tip/sched] INFO: suspicious RCU usage | From | Peter Zijlstra <> | Date | Wed, 07 Dec 2011 14:28:05 +0100 |
| |
On Wed, 2011-12-07 at 15:39 +0800, Yong Zhang wrote: > =============================== > [ INFO: suspicious RCU usage. ] > ------------------------------- > /build/linux/kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > > rcu_scheduler_active = 1, debug_locks = 1 > 1 lock held by swapper/0/1: > #0: (&sb->s_type->i_mutex_key#2){+.+.+.}, at: [<ffffffff812a0e0c>] debugfs_create_file+0x8c/0x270 > > stack backtrace: > Pid: 1, comm: swapper/0 Not tainted 3.2.0-rc1-00339-gcd490c5 #14 > Call Trace: > <IRQ> [<ffffffff815f9968>] ? _raw_spin_unlock_irqrestore+0x38/0x80 > [<ffffffff8109407f>] lockdep_rcu_suspicious+0xbf/0xe0 > [<ffffffff8107dd48>] trigger_load_balance+0x5b8/0x5c0 > [<ffffffff81070544>] scheduler_tick+0x104/0x160 > [<ffffffff8104a1ce>] update_process_times+0x6e/0x90 > [<ffffffff8108e32c>] tick_periodic+0x2c/0x70 > [<ffffffff8108e394>] tick_handle_periodic+0x24/0x80 > [<ffffffff812a07a7>] ? T.562+0xf7/0x170 > [<ffffffff815fce56>] smp_apic_timer_interrupt+0x66/0x98 > [<ffffffff815fb2f0>] apic_timer_interrupt+0x70/0x80 > <EOI> [<ffffffff810984a4>] ? lock_release+0xe4/0x2b0 > [<ffffffff815f98f3>] _raw_spin_unlock+0x23/0x60 > [<ffffffff812a07a7>] T.562+0xf7/0x170 > [<ffffffff812a0e71>] debugfs_create_file+0xf1/0x270 > [<ffffffff810e96c9>] trace_create_file+0x19/0x50 > [<ffffffff81af7b3c>] tracer_init_debugfs+0x2bd/0x3c0 > [<ffffffff810e96c9>] ? trace_create_file+0x19/0x50 > [<ffffffff81af787f>] ? clear_boot_tracer+0x2d/0x2d > [<ffffffff810001d3>] do_one_initcall+0x43/0x180 > [<ffffffff81adf637>] kernel_init+0xd0/0x156 > [<ffffffff815fc574>] kernel_thread_helper+0x4/0x10 > [<ffffffff8106fdb8>] ? finish_task_switch+0x88/0xf0 > [<ffffffff815f99eb>] ? _raw_spin_unlock_irq+0x3b/0x70 > [<ffffffff815f9f61>] ? retint_restore_args+0xe/0xe > [<ffffffff81adf567>] ? parse_early_options+0x20/0x20 > [<ffffffff815fc570>] ? gs_change+0xb/0xb > > Seems due to commit [0b005cf5: sched, nohz: Implement sched group, domain > aware nohz idle load balancing]
I think something like the below should suffice, the sd argument only lives inside the for_each_domain() so wrapping the whole block should suffice.
--- kernel/sched/fair.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6482136..a4d2b7a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5088,23 +5088,28 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu) if (rq->nr_running >= 2) goto need_kick; + rcu_read_lock(); for_each_domain(cpu, sd) { struct sched_group *sg = sd->groups; struct sched_group_power *sgp = sg->sgp; int nr_busy = atomic_read(&sgp->nr_busy_cpus); if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) - goto need_kick; + goto need_kick_unlock; if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) - goto need_kick; + goto need_kick_unlock; if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING))) break; } + rcu_read_unlock(); return 0; + +need_kick_unlock: + rcu_read_unlock(); need_kick: return 1; }
| |