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| author | Frederic Weisbecker <fweisbec@gmail.com> | 2011-10-07 16:31:02 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-12-11 10:31:38 -0800 |
| commit | 416eb33cd60ef405e2860a186364e57bcb2d89f6 (patch) | |
| tree | c8c67e399b99246ce47a411b3518d4365f139606 /kernel/softirq.c | |
| parent | 98ad1cc14a5c4fd658f9d72c6ba5c86dfd3ce0d5 (diff) | |
| download | lwn-416eb33cd60ef405e2860a186364e57bcb2d89f6.tar.gz lwn-416eb33cd60ef405e2860a186364e57bcb2d89f6.zip | |
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.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c index f9f2aa81ce53..4eb3a0fa351e 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(); } |