From cd95851785bcfe95fdf73689e8ecb5a1c5959231 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 17 Aug 2008 07:37:15 -0700 Subject: rcu: fix classic RCU locking cleanup lockdep problem On Fri, Aug 15, 2008 at 04:24:30PM +0200, Ingo Molnar wrote: > > Paul, > > one of your two recent RCU patches caused this lockdep splat in -tip > testing: > > -------------------> > Brought up 2 CPUs > Total of 2 processors activated (6850.87 BogoMIPS). > PM: Adding info for No Bus:platform > khelper used greatest stack depth: 3124 bytes left > > ================================= > [ INFO: inconsistent lock state ] > 2.6.27-rc3-tip #1 > --------------------------------- > inconsistent {softirq-on-W} -> {in-softirq-W} usage. > ksoftirqd/0/4 [HC0[0]:SC1[1]:HE1:SE0] takes: > (&rcu_ctrlblk.lock){-+..}, at: [] __rcu_process_callbacks+0x1ac/0x1f0 > {softirq-on-W} state was registered at: > [] __lock_acquire+0x3f4/0x5b0 > [] lock_acquire+0x89/0xc0 > [] _spin_lock+0x3b/0x70 > [] rcu_init_percpu_data+0x29/0x80 > [] rcu_cpu_notify+0xaf/0xd0 > [] notifier_call_chain+0x2d/0x60 > [] __raw_notifier_call_chain+0x1e/0x30 > [] _cpu_up+0x79/0x110 > [] cpu_up+0x4d/0x70 > [] kernel_init+0xb1/0x200 > [] kernel_thread_helper+0x7/0x10 > [] 0xffffffff > irq event stamp: 14 > hardirqs last enabled at (14): [] trace_hardirqs_on+0xb/0x10 > hardirqs last disabled at (13): [] trace_hardirqs_off+0xb/0x10 > softirqs last enabled at (0): [] copy_process+0x276/0x1190 > softirqs last disabled at (11): [] call_on_stack+0x1a/0x30 > > other info that might help us debug this: > no locks held by ksoftirqd/0/4. > > stack backtrace: > Pid: 4, comm: ksoftirqd/0 Not tainted 2.6.27-rc3-tip #1 > [] print_usage_bug+0x16c/0x1b0 > [] mark_lock+0xa75/0xb10 > [] ? sched_clock+0x15/0x30 > [] __lock_acquire+0x3ad/0x5b0 > [] lock_acquire+0x89/0xc0 > [] ? __rcu_process_callbacks+0x1ac/0x1f0 > [] _spin_lock+0x3b/0x70 > [] ? __rcu_process_callbacks+0x1ac/0x1f0 > [] __rcu_process_callbacks+0x1ac/0x1f0 > [] rcu_process_callbacks+0x26/0x50 > [] __do_softirq+0x95/0x120 > [] ? __do_softirq+0x0/0x120 > [] call_on_stack+0x1a/0x30 > [] ? ksoftirqd+0x96/0x110 > [] ? ksoftirqd+0x0/0x110 > [] ? kthread+0x47/0x80 > [] ? kthread+0x0/0x80 > [] ? kernel_thread_helper+0x7/0x10 > ======================= > calling init_cpufreq_transition_notifier_list+0x0/0x20 > initcall init_cpufreq_transition_notifier_list+0x0/0x20 returned 0 after 0 msecs > calling net_ns_init+0x0/0x190 > net_namespace: 676 bytes > initcall net_ns_init+0x0/0x190 returned 0 after 0 msecs > calling cpufreq_tsc+0x0/0x20 > initcall cpufreq_tsc+0x0/0x20 returned 0 after 0 msecs > calling reboot_init+0x0/0x20 > initcall reboot_init+0x0/0x20 returned 0 after 0 msecs > calling print_banner+0x0/0x10 > Booting paravirtualized kernel on bare hardware > > <----------------------- > > my guess is on: > > commit 1f7b94cd3d564901f9e04a8bc5832ae7bfd690a0 > Author: Paul E. McKenney > Date: Tue Aug 5 09:21:44 2008 -0700 > > rcu: classic RCU locking and memory-barrier cleanups > > Ingo Fixes a problem detected by lockdep in which rcu->lock was acquired both in irq context and in process context, but without disabling from process context. Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- kernel/rcuclassic.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'kernel/rcuclassic.c') diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c index 5de126630b1..fb1f1cc4514 100644 --- a/kernel/rcuclassic.c +++ b/kernel/rcuclassic.c @@ -700,7 +700,9 @@ void rcu_check_callbacks(int cpu, int user) static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, struct rcu_data *rdp) { - spin_lock(&rcp->lock); + long flags; + + spin_lock_irqsave(&rcp->lock, flags); memset(rdp, 0, sizeof(*rdp)); rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist; rdp->donetail = &rdp->donelist; @@ -708,7 +710,7 @@ static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, rdp->qs_pending = 0; rdp->cpu = cpu; rdp->blimit = blimit; - spin_unlock(&rcp->lock); + spin_unlock_irqrestore(&rcp->lock, flags); } static void __cpuinit rcu_online_cpu(int cpu) -- cgit v1.2.3