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authorFrederic Weisbecker <fweisbec@gmail.com>2011-10-07 16:31:02 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-12-11 10:31:38 -0800
commit416eb33cd60ef405e2860a186364e57bcb2d89f6 (patch)
treec8c67e399b99246ce47a411b3518d4365f139606 /kernel/softirq.c
parent98ad1cc14a5c4fd658f9d72c6ba5c86dfd3ce0d5 (diff)
rcu: Fix early call to rcu_idle_enter()
On the irq exit path, tick_nohz_irq_exit() may raise a softirq, which action leads to the wake up path and select_task_rq_fair() that makes use of rcu to iterate the domains. This is an illegal use of RCU because we may be in RCU extended quiescent state if we interrupted an RCU-idle window in the idle loop: [ 132.978883] =============================== [ 132.978883] [ INFO: suspicious RCU usage. ] [ 132.978883] ------------------------------- [ 132.978883] kernel/sched_fair.c:1707 suspicious rcu_dereference_check() usage! [ 132.978883] [ 132.978883] other info that might help us debug this: [ 132.978883] [ 132.978883] [ 132.978883] rcu_scheduler_active = 1, debug_locks = 0 [ 132.978883] RCU used illegally from extended quiescent state! [ 132.978883] 2 locks held by swapper/0: [ 132.978883] #0: (&p->pi_lock){-.-.-.}, at: [<ffffffff8105a729>] try_to_wake_up+0x39/0x2f0 [ 132.978883] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff8105556a>] select_task_rq_fair+0x6a/0xec0 [ 132.978883] [ 132.978883] stack backtrace: [ 132.978883] Pid: 0, comm: swapper Tainted: G W 3.0.0+ #178 [ 132.978883] Call Trace: [ 132.978883] <IRQ> [<ffffffff810a01f6>] lockdep_rcu_suspicious+0xe6/0x100 [ 132.978883] [<ffffffff81055c49>] select_task_rq_fair+0x749/0xec0 [ 132.978883] [<ffffffff8105556a>] ? select_task_rq_fair+0x6a/0xec0 [ 132.978883] [<ffffffff812fe494>] ? do_raw_spin_lock+0x54/0x150 [ 132.978883] [<ffffffff810a1f2d>] ? trace_hardirqs_on+0xd/0x10 [ 132.978883] [<ffffffff8105a7c3>] try_to_wake_up+0xd3/0x2f0 [ 132.978883] [<ffffffff81094f98>] ? ktime_get+0x68/0xf0 [ 132.978883] [<ffffffff8105aa35>] wake_up_process+0x15/0x20 [ 132.978883] [<ffffffff81069dd5>] raise_softirq_irqoff+0x65/0x110 [ 132.978883] [<ffffffff8108eb65>] __hrtimer_start_range_ns+0x415/0x5a0 [ 132.978883] [<ffffffff812fe3ee>] ? do_raw_spin_unlock+0x5e/0xb0 [ 132.978883] [<ffffffff8108ed08>] hrtimer_start+0x18/0x20 [ 132.978883] [<ffffffff8109c9c3>] tick_nohz_stop_sched_tick+0x393/0x450 [ 132.978883] [<ffffffff810694f2>] irq_exit+0xd2/0x100 [ 132.978883] [<ffffffff81829e96>] do_IRQ+0x66/0xe0 [ 132.978883] [<ffffffff81820d53>] common_interrupt+0x13/0x13 [ 132.978883] <EOI> [<ffffffff8103434b>] ? native_safe_halt+0xb/0x10 [ 132.978883] [<ffffffff810a1f2d>] ? trace_hardirqs_on+0xd/0x10 [ 132.978883] [<ffffffff810144ea>] default_idle+0xba/0x370 [ 132.978883] [<ffffffff810147fe>] amd_e400_idle+0x5e/0x130 [ 132.978883] [<ffffffff8100a9f6>] cpu_idle+0xb6/0x120 [ 132.978883] [<ffffffff817f217f>] rest_init+0xef/0x150 [ 132.978883] [<ffffffff817f20e2>] ? rest_init+0x52/0x150 [ 132.978883] [<ffffffff81ed9cf3>] start_kernel+0x3da/0x3e5 [ 132.978883] [<ffffffff81ed9346>] x86_64_start_reservations+0x131/0x135 [ 132.978883] [<ffffffff81ed944d>] x86_64_start_kernel+0x103/0x112 Fix this by calling rcu_idle_enter() after tick_nohz_irq_exit(). Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/softirq.c')
-rw-r--r--kernel/softirq.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c
index f9f2aa81ce5..4eb3a0fa351 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -347,12 +347,12 @@ void irq_exit(void)
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
- rcu_irq_exit();
#ifdef CONFIG_NO_HZ
/* Make sure that timer wheel updates are propagated */
if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
tick_nohz_irq_exit();
#endif
+ rcu_irq_exit();
preempt_enable_no_resched();
}